Note: Descriptions are shown in the official language in which they were submitted.
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Title: SYSTEM AND METHOD FOR ENABLING BULK RETRIEVAL OF
CERTIFICATES
Field of the Invention
[0001] The invention relates generally to the processing of messages,
such as e-mail messages, and more specifically to a system and method for
searching and retrieving certificates used in the processing of encoded
messages.
Background of the Invention
[0002] Electronic mail ("e-mail") messages may be encoded using one of a
number of known protocols. Some of these protocols, such as Secure Multiple
Internet Mail Extensions ("S/MIME") for example, rely on public and private
encryption keys to provide confidentiality and integrity, and on a Public Key
Infrastructure (PKI) to communicate information that provides authentication
and
authorization. Data encrypted using a private key of a private key/public key
pair
can only be decrypted using the corresponding public key of the pair, and vice-
versa. The authenticity of public keys used in the encoding of messages is
validated using certificates. In particular, if a user of a computing device
wishes
to encrypt a message before the message is sent to a particular individual,
the
user will require a certificate for that individual. That certificate will
typically
comprise the public key of the individual, as well as other identification-
related
information.
[0003] If the requisite certificate for the intended recipient is not already
stored on the user's computing device, the certificate must first be
retrieved.
Searching for and retrieving a certificate for a specific recipient is a
process that
generally involves querying a certificate server by having the user manually
enter
the name and/or e-mail address of the intended recipient in a search form
displayed on the computing device. Certificates located in the search are then
temporarily downloaded to the computing device for consideration, and a list
of
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located certificates may be displayed to the user. Selected certificates in
the list
may then be manually identified by a user for storage in a non-volatile store
of
the computing device, for potential future use.
[0004] Many organizations set up their own certificate servers that contain
all of the certificates that have been issued to people in the organization
who are
able to send and receive encoded messages. If an individual in the
organization
plans to communicate with other individuals in the organization, the
certificates of
these other individuals will potentially need to be obtained. Manually
searching
for certificates issued to particular individuals in an organization, as they
become
needed, can be inconvenient and time-consuming. Furthermore, manual
searching for certificates may be particularly cumbersome if the computing
device on which the certificate searches are initiated is small in size (e.g.
a
mobile device). It might not also be clear who is enabled to send and receive
encoded messages within an organization, and therefore some attempted
certificate searches may not return the desired results, if any results are
returned
at all.
Summary of the Invention
[0005] Embodiments of the invention are generally directed to a system
and method for searching and retrieving certificates that automates at least
some
of the tasks typically performed manually by users in known techniques, and
which may be employed by individuals within an organization to more
efficiently
exchange encoded messages with other individuals in the organization that are
able to do so. More specifically, embodiments of the invention may be employed
to retrieve large numbers of certificates from one or more certificate
servers.
[0006] In one broad aspect of the invention, there is provided a method for
searching and retrieving certificates comprising the steps of: performing a
search
on each of one or more certificate servers for a plurality of certificates,
wherein at
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least one query is submitted to the respective certificate server to request
retrieval of the respective plurality of certificates; for each certificate
server that
returns all of the respective plurality of certificates as a result of the
search
performed thereon, downloading the respective plurality of certificates to the
computing device; for each certificate server that does not return all of the
respective plurality of certificates as a result of the search performed
thereon,
performing the substeps of dividing the respective search into a plurality of
subsearches, performing the subsearches recursively, wherein at least one
query
is submitted to the respective certificate server for each subsearch, wherein
the
respective certificate server returns at least a subset of the respective
plurality of
certificates as a collective result of the subsearches of the respective
search, and
downloading the at least a subset of the respective plurality of certificates
to the
computing device; and storing at least a subset of certificates downloaded to
the
computing device in one or more certificate stores.
[0007] In another broad aspect of the invention, the steps are performed
by a certificate synchronization application executing and residing on the
computing device upon initiation of the search by a user.
[0008] In another broad aspect of the invention, the storing step comprises
storing at least a subset of certificates downloaded to the computing device
in a
certificate store on the computing device and/or in a certificate store on a
mobile
device.
[0009] In another broad aspect of the invention, the method further
comprises the steps of: generating a list of certificates identifying one or
more
certificates downloaded to the computing device; displaying the list to a
user; and
receiving user selections of selected certificates identified in the list;
wherein the
at least a subset of certificates stored in the storing step comprises the
selected
certificates.
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[0010] In another broad aspect of the invention, the method further
comprises the step of filtering out duplicate downloaded certificates prior to
the
storing step.
[0011] In another broad aspect of the invention, the dividing substep
comprises dividing the respective search into subsearches, each subsearch for
searching certificates issued to names beginning with one of a plurality of
prefixes, such as a letter of the alphabet, for example.
Brief Description of the Drawings
[0012] For a better understanding of embodiments of the invention, and to
show more clearly how it may be carried into effect, reference will now be
made,
by way of example, to the accompanying drawings in which:
FIG. 1 is a block diagram of a mobile device in one example implementation;
FIG. 2 is a block diagram of a communication subsystem component of the
mobile device of FIG. 1;
FIG. 3 is a block diagram of a node of a wireless network;
FIG. 4 is a block diagram illustrating components of a host system in one
example configuration;
FIG. 5 is a block diagram showing an example of a certificate chain;
FIG. 6 is a block diagram illustrating components of an example of an encoded
message;
FIG. 7A is a flowchart illustrating steps in a method of searching and
retrieving
certificates in an embodiment of the invention; and
FIG. 7B is a flowchart illustrating steps in a method of searching and
retrieving
certificates in another embodiment of the invention.
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Detailed Description of Embodiments of the Invention
[0013] Some embodiments of the invention make use of a mobile station.
A mobile station is a two-way communication device with advanced data
communication capabilities having the capability to communicate with other
computer systems, and is also referred to herein generally as a mobile device.
A
mobile device may also include the capability for voice communications.
Depending on the functionality provided by a mobile device, it may be referred
to
as a data messaging device, a two-way pager, a cellular telephone with data
messaging capabilities, a wireless Internet appliance, or a data communication
device (with or without telephony capabilities). A mobile device communicates
with other devices through a network of transceiver stations.
[0014] To aid the reader in understanding the structure of a mobile device
and how it communicates with other devices, reference is made to FIGS. 1
through 3.
[0015] Referring first to FIG. 1, a block diagram of a mobile device in one
example implementation is shown generally as 100. Mobile device 100
comprises a number of components, the controlling component being
microprocessor 102. Microprocessor 102 controls the overall operation of
mobile
device 100. Communication functions, including data and voice communications,
are performed through communication subsystem 104. Communication
subsystem 104 receives messages from and sends messages to a wireless
network 200. In this example implementation of mobile device 100,
communication subsystem 104 is configured in accordance with the Global
System for Mobile Communication (GSM) and General Packet Radio Services
(GPRS) standards. The GSM/GPRS wireless network is used worldwide and it is
expected that these standards will be superseded eventually by Enhanced Data
GSM Environment (EDGE) and Universal Mobile Telecommunications Service
(UMTS). New standards are still being defined, but it is believed that they
will
have similarities to the network behaviour described herein, and it will also
be
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understood by persons skilled in the art that the invention is intended to use
any
other suitable standards that are developed in the future. The wireless link
connecting communication subsystem 104 with network 200 represents one or
more different Radio Frequency (RF) channels, operating according to defined
protocols specified for GSM/GPRS communications. With newer network
protocols, these channels are capable of supporting both circuit switched
voice
communications and packet switched data communications.
[0016] Although the wireless network associated with mobile device 100 is
a GSM/GPRS wireless network in one example implementation of mobile device
100, other wireless networks may also be associated with mobile device 100 in
variant implementations. Different types of wireless networks that may be
employed include, for example, data-centric wireless networks, voice-centric
wireless networks, and dual-mode networks that can support both voice and data
communications over the same physical base stations. Combined dual-mode
networks include, but are not limited to, Code Division Multiple Access (CDMA)
or CDMA2000 networks, GSM/GPRS networks (as mentioned above), and future
third-generation (3G) networks like EDGE and UMTS. Some older examples of
data-centric networks include the MobitexTM Radio Network and the DataTACTM
Radio Network. Examples of older voice-centric data networks include Personal
Communication Systems (PCS) networks like GSM and Time Division Multiple
Access (TDMA) systems.
[0017] Microprocessor 102 also interacts with additional subsystems such
as a Random Access Memory (RAM) 106, flash memory 108, display 110,
auxiliary input/output (I/O) subsystem 112, serial port 114, keyboard 116,
speaker 118, microphone 120, short-range communications 122 and other
devices 124.
[0018] Some of the subsystems of mobile device 100 perform
communication-related functions, whereas other subsystems may provide
"resident" or on-device functions. By way of example, display 110 and keyboard
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116 may be used for both communication-related functions, such as entering a
text message for transmission over network 200, and device-resident functions
such as a calculator or task list. Operating system software used by
microprocessor 102 is typically stored in a persistent store such as flash
memory
108, which may alternatively be a read-only memory (ROM) or similar storage
element (not shown). Those skilled in the art will appreciate that the
operating
system, specific device applications, or parts thereof, may be temporarily
loaded
into a volatile store such as RAM 106.
[0019] Mobile device 100 may send and receive communication signals
over network 200 after required network registration or activation procedures
have been completed. Network access is associated with a subscriber or user of
a mobile device 100. To identify a subscriber, mobile device 100 requires a
Subscriber Identity Module or "SIM" card 126 to be inserted in a SIM interface
128 in order to communicate with a network. SIM 126 is one type of a
conventional "smart card" used to identify a subscriber of mobile device 100
and
to personalize the mobile device 100, among other things. Without SIM 126,
mobile device 100 is not fully operational for communication with network 200.
By inserting SIM 126 into SIM interface 128, a subscriber can access all
subscribed services. Services. could include: web browsing and messaging such
as e-mail, voice mail, Short Message Service (SMS), and Multimedia Messaging
Services (MMS). More advanced services may include: point of sale, field
service and sales force automation. SIM 126 includes a processor and memory
for storing information. Once SIM 126 is inserted in SIM interface 128, it is
coupled to microprocessor 102. In order to identify the subscriber, SIM 126
contains some user parameters such as an International Mobile Subscriber
Identity (IMSI). An advantage of using SIM 126 is that a subscriber is not
necessarily bound by any single physical mobile device. SIM 126 may store
additional subscriber information for a mobile device as well, including
datebook
(or calendar) information and recent call information.
-------
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[0020] Mobile device 100 is a battery-powered device and includes a
battery interface 132 for receiving one or more rechargeable batteries 130.
Battery interface 132 is coupled to a regulator (not shown), which assists
battery
130 in providing power V+ to mobile device 100. Although current technology
makes use of a battery, future technologies such as micro fuel cells may
provide
the power to mobile device 100.
[0021] Microprocessor 102, in addition to its operating system functions,
enables execution of software applications on mobile device 100. A set of
applications that control basic device operations, including data and voice
communication applications, will normally be installed on mobile device 100
during its manufacture. Another application that may be loaded onto mobile
device 100 would be a personal information manager (PIM). A PIM has
functionality to organize and manage data items of interest to a subscriber,
such
as, but not limited to, e-mail, calendar events, voice mails, appointments,
and
task items. A PIM application has the ability to send and receive data items
via
wireless network 200. PIM data items may be seamlessly integrated,
synchronized, and updated via wireless network 200 with the mobile device
subscriber's corresponding data items stored and/or associated with a host
computer system. This functionality creates a mirrored host computer on mobile
device 100 with respect to such items. This can be particularly advantageous
where the host computer system is the mobile device subscriber's office
computer system.
[0022] Additional applications may also be loaded onto mobile device 100
through network 200, auxiliary I/O subsystem 112, serial port 114, short-range
communications subsystem 122, or any other suitable subsystem 124. This
flexibility in application installation increases the functionality of mobile
device
100 and may provide enhanced on-device functions, communication-related
functions, or both. For example, secure communication applications may enable
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electronic commerce functions and other such financial transactions to be
performed using mobile device 100.
[0023] Serial port 114 enables a subscriber to set preferences through an
external device or software application and extends the capabilities of mobile
device 100 by providing for information or software downloads to mobile device
100 other than through a wireless communication network. The alternate
download path may, for example, be used to load an encryption key onto mobile
device 100 through a direct and thus reliable and trusted connection to
provide
secure device communication.
[0024] Short-range communications subsystem 122 provides for
communication between mobile device 100 and different systems or devices,
without the use of network 200. For example, subsystem 122 may include an
infrared device and associated circuits and components for short-range
communication. Examples of short range communication would include
standards developed by the Infrared Data Association (IrDA), Bluetooth and
the 802.11 family of standards developed by IEEE.
[0025] In use, a received signal such as a text message, an e-mail
message, or web page download will be processed by communication
subsystem 104 and input to microprocessor 102. Microprocessor 102 will then
process the received signal for output to display 110 or alternatively to
auxiliary
I/O subsystem 112. A subscriber may also compose data items, such as e-mail
messages, for example, using keyboard 116 in conjunction with display 110 and
possibly auxiliary I/O subsystem 112. Auxiliary subsystem 112 may include
devices such as: a touch screen, mouse, track ball, infrared fingerprint
detector,
or a roller wheel with dynamic button pressing capability. Keyboard 116 is an
alphanumeric keyboard and/or telephone-type keypad. A composed item may
be transmitted over network 200 through communication subsystem 104.
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[0026] For voice communications, the overall operation of mobile device
100 is substantially similar, except that the received signals would be output
to
speaker 118, and signals for transmission would be generated by microphone
120. Alternative voice or audio I/O subsystems, such as a voice message
recording subsystem, may also be implemented on mobile device 100. Although
voice or audio signal output is accomplished primarily through speaker 118,
display 110 may also be used to provide additional information such as the
identity of a calling party, duration of a voice call, or other voice call
related
information.
[0027] Referring now to FIG. 2, a block diagram of the communication
subsystem component 104 of FIG. 1 is shown. Communication subsystem 104
comprises a receiver 150, a transmitter 152, one or more embedded or internal
antenna elements 154, 156, Local Oscillators (LOs) 158, and a processing
module such as a Digital Signal Processor (DSP) 160.
[0028] The particular design of communication subsystem 104 is
dependent upon the network 200 in which mobile device 100 is intended to
operate, thus it should be understood that the design illustrated in FIG. 2
serves
only as one example. Signals received by antenna 154 through network 200 are
input to receiver 150, which may perform such common receiver functions as
signal amplification, frequency down conversion, filtering, channel selection,
and
analog-to-digital (AID) conversion. A/D conversion of a received signal allows
more complex communication functions such as demodulation and decoding to
be performed in DSP 160. In a similar manner, signals to be transmitted are
processed, including modulation and encoding, by DSP 160. These DSP-
processed signals are input to transmitter 152 for digital-to-analog (D/A)
conversion, frequency up conversion, filtering, amplification and transmission
over network 200 via antenna 156. DSP 160 not only processes communication
signals, but also provides for receiver and transmitter control. For example,
the
gains applied to communication signals in receiver 150 and transmitter 152 may
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be adaptively controlled through automatic gain control algorithms implemented
in DSP 160.
[0029] The wireless link between mobile device 100 and a network 200
may contain one or more different channels, typically different RF channels,
and
associated protocols used between mobile device 100 and network 200. A RF
channel is a limited resource that must be conserved, typically due to limits
in
overall bandwidth and limited battery power of mobile device 100.
[0030] When mobile device 100 is fully operational, transmitter 152 is
typically keyed or turned on only when it is sending to network 200 and is
otherwise turned off to conserve resources. Similarly, receiver 150 is
periodically
turned off to conserve power until it is needed to receive signals or
information (if
at all) during designated time periods.
[0031] Referring now to FIG. 3, a block diagram of a node of a wireless
network is shown as 202. In practice, network 200 comprises one or more nodes
202. Mobile device 100 communicates with a node 202 within wireless network
200. In the example implementation of FIG. 3, node 202 is configured in
accordance with General Packet Radio Service (GPRS) and Global Systems for
Mobile (GSM) technologies. Node 202 includes a base station controller (BSC)
204 with an associated tower station 206, a Packet Control Unit (PCU) 208
added for GPRS support in GSM, a Mobile Switching Center (MSC) 210, a Home
Location Register (HLR) 212, a Visitor Location Registry (VLR) 214, a Serving
GPRS Support Node (SGSN) 216, a Gateway GPRS Support Node (GGSN)
218, and a Dynamic Host Configuration Protocol (DHCP) 220. This list of
components is not meant to be an exhaustive list of the components of every
node 202 within a GSM/GPRS network, but rather a list of components that are
commonly used in communications through network 200.
[0032] In a GSM network, MSC 210 is coupled to BSC 204 and to a
landline network, such as a Public Switched Telephone Network (PSTN) 222 to
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satisfy circuit switched requirements. The connection through PCU 208, SGSN
216 and GGSN 218 to the public or private network (Internet) 224 (also
referred
to herein generally as a shared network infrastructure) represents the data
path
for GPRS capable mobile devices. In a GSM network extended with GPRS
capabilities, BSC 204 also contains a Packet Control Unit (PCU) 208 that
connects to SGSN 216 to control segmentation, radio channel allocation and to
satisfy packet switched requirements. To track mobile device location and
availability for both circuit switched and packet switched management, HLR 212
is shared between MSC 210 and SGSN 216. Access to VLR 214 is controlled by
MSC 210.
[0033] Station 206 is a fixed transceiver station. Station 206 and BSC 204
together form the fixed transceiver equipment. The fixed transceiver equipment
provides wireless network coverage for a particular coverage area commonly
referred to as a "cell". The fixed transceiver equipment transmits
communication
signals to and receives communication signals from mobile devices within its
cell
via station 206. The fixed transceiver equipment normally performs such
functions as modulation and possibly encoding and/or encryption of signals to
be
transmitted to the mobile device in accordance with particular, usually
predetermined, communication protocols and parameters, under control of its
controller. The fixed transceiver equipment similarly demodulates and possibly
decodes and decrypts, if necessary, any communication signals received from
mobile device 100 within its cell. Communication protocols and parameters may
vary between different nodes. For example, one node may employ a different
modulation scheme and operate at different frequencies than other nodes.
[0034] For all mobile devices 100 registered with a specific network,
permanent configuration data such as a user profile is stored in HLR 212. HLR
212 also contains location information for each registered mobile device and
can
be queried to determine the current location of a mobile device. MSC 210 is
responsible for a group of location areas and stores the data of the mobile
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devices currently in its area of responsibility in VLR 214. Further VLR 214
also
contains information on mobile devices that are visiting other networks. The
information in VLR 214 includes part of the permanent mobile device data
transmitted from HLR 212 to VLR 214 for faster access. By moving additional
information from a remote HLR 212 node to VLR 214, the amount of traffic
between these nodes can be reduced so that voice and data services can be
provided with faster response times and at the same time requiring less use of
computing resources.
[0035] SGSN 216 and GGSN 218 are elements added for GPRS support;
namely packet switched data support, within GSM. SGSN 216 and MSC 210
have similar responsibilities within wireless network 200 by keeping track of
the
location of each mobile device 100. SGSN 216 also performs security functions
and access control for data traffic on network 200. GGSN 218 provides
internetworking connections with external packet switched networks and
connects to one or more SGSN's 216 via an Internet Protocol (IP) backbone
network operated within the network 200. During normal operations, a given
mobile device 100 must perform a "GPRS Attach" to acquire an IP address and
to access data services. This requirement is not present in circuit switched
voice
channels as Integrated Services Digital Network (ISDN) addresses are used for
routing incoming and outgoing calls. Currently, all GPRS capable networks use
private, dynamically assigned IP addresses, thus requiring a DHCP server 220
connected to the GGSN 218. There are many mechanisms for dynamic IP
assignment, including using a combination of a Remote Authentication Dial-In
User Service (RADIUS) server and DHCP server. Once the GPRS Attach is
complete, a logical connection is established from a mobile device 100,
through
PCU 208, and SGSN 216 to an Access Point Node (APN) within GGSN 218.
The APN represents a logical end of an IP tunnel that can either access direct
Internet compatible services or private network connections. The APN also
represents a security mechanism for network 200, insofar as each mobile device
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100 must be assigned to one or more APNs and mobile devices 100 cannot
exchange data without first performing a GPRS Attach to an APN that it has
been
authorized to use. The APN may be considered to be similar to an Internet
domain name such as "myconnection.wireless.com".
[0036] Once the GPRS Attach is complete, a tunnel is created and all
traffic is exchanged within standard IP packets using any protocol that can be
supported in IP packets. This includes tunneling methods such as IP over IP as
in the case with some IPSecurity (IPsec) connections used with Virtual Private
Networks (VPN). These tunnels are also referred to as Packet Data Protocol
(PDP) Contexts and there are a limited number of these available in the
network
200. To maximize use of the PDP Contexts, network 200 will run an idle timer
for
each PDP Context to determine if there is a lack of activity. When a mobile
device 100 is not using its PDP Context, the PDP Context can be deallocated
and the IP address returned to the IP address pool managed by DHCP server
220.
[0037] Referring now to FIG. 4, a block diagram illustrating components of
a host system in one example configuration is shown. Host system 250 will
typically be a corporate office or other local area network (LAN), but may
instead
be a home office computer or some other private system, for example, in
variant
implementations. In this example shown in FIG. 4, host system 250 is depicted
as a LAN of an organization to which a user of mobile device 100 belongs.
[0038] LAN 250 comprises a number of network components connected to
each other by LAN connections 260. For instance, a user's desktop computer
262a with an accompanying cradle 264 for the user's mobile device 100 is
situated on LAN 250. Cradle 264 for mobile device 100 may be coupled to
computer 262a by a serial or a Universal Serial Bus (USB) connection, for
example. Other user computers 262b are also situated on LAN 250, and each
may or may not be equipped with an accompanying cradle 264 for a mobile
device. Cradle 264 facilitates the loading of information (e.g. PIM data,
private
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symmetric encryption keys to facilitate secure communications between mobile
device 100 and LAN 250) from user computer 262a to mobile device 100, and
may be particularly useful for bulk information updates often performed in
initializing mobile device 100 for use. The information downloaded to mobile
device 100 may include certificates used in the exchange of messages. It will
be
understood by persons skilled in the art that user computers 262a, 262b will
typically be also connected to other peripheral devices not explicitly shown
in
FIG. 4.
[0039] Embodiments of the invention relate generally to the processing of
messages, such as e-mail messages, and some embodiments relate generally to
the communication of such messages to and from mobile device 100.
Accordingly, only a subset of network components of LAN 250 are shown in FIG.
4 for ease of exposition, and it will be understood by persons skilled in the
art
that LAN 250 will comprise additional components not explicitly shown in FIG.
4,
for this example configuration. More generally, LAN 250 may represent a
smaller
part of a larger network [not shown] of the organization, and may comprise
different components and/or be arranged in different topologies than that
shown
in the example of FIG. 4.
[0040] In this example, mobile device 100 communicates with LAN 250
through a node 202 of wireless network 200 and a shared network infrastructure
224 such as a service provider network or the public Internet. Access to LAN
250 may be provided through one or more routers [not shown], and computing
devices of LAN 250 may operate from behind a firewall or proxy server 266.
[0041] In a variant implementation, LAN 250 comprises a wireless VPN
router [not shown] to facilitate data exchange between the LAN 250 and mobile
device 100. The concept of a wireless VPN router is new in the wireless
industry
and implies that a VPN connection can be established directly through a
specific
wireless network to mobile device 100. The possibility of using a wireless VPN
router has only recently been available and could be used when the new
Internet
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Protocol (IP) Version 6 (IPV6) arrives into IP-based wireless networks. This
new
protocol will provide enough IP addresses to dedicate an IP address to every
mobile device, making it possible to push information to a mobile device at
any
time. An advantage of using a wireless VPN router is that it could be an off-
the-
shelf VPN component, not requiring a separate wireless gateway and separate
wireless infrastructure to be used. A VPN connection would preferably be a
Transmission Control Protocol (TCP)/IP or User Datagram Protocol (UDP)/IP
connection to deliver the messages directly to mobile device 100 in this
variant
implementation.
[0042] Messages intended for a user of mobile device 100 are initially
received by a message server 268 of LAN 250. Such messages may originate
from any of a number of sources. For instance, a message may have been sent
by a sender from a computer 262b within LAN 250, from a different mobile
device
[not shown] connected to wireless network 200 or to a different wireless
network,
or from a different computing device or other device capable of sending
messages, via the shared network infrastructure 224, and possibly through an
application service provider (ASP) or Internet service provider (ISP), for
example.
[0043] Message server 268 typically acts as the primary interface for the
exchange of messages, particularly e-mail messages, within the organization
and
over the shared network infrastructure 224. Each user in the organization that
has been set up to send and receive messages is typically associated with a
user
account managed by message server 268. One example of a message server
268 is a Microsoft ExchangeTM Server. In some implementations, LAN 250 may
comprise multiple message servers 268. Message server 268 may also be
adapted to provide additional functions beyond message management, including
the management of data associated with calendars and task lists, for example.
[0044] When messages are received by message server 268, they are
typically stored in a message store [not explicitly shown], from which
messages
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can be subsequently retrieved and delivered to users. For instance, an e-mail
client application operating on a user's computer 262a may request the e-mail
messages associated with that user's account stored on message server 268.
These messages would then typically be retrieved from message server 268 and
stored locally on computer 262a.
[0045] When operating mobile device 100, the user may wish to have e-
mail messages retrieved for delivery to the handheld. An e-mail client
application
operating on mobile device 100 may also request messages associated with the
user's account from message server 268. The e-mail client may be configured
(either by the user or by an administrator, possibly in accordance with an
organization's information technology (IT) policy) to make this request at the
direction of the user, at some pre-defined time interval, or upon the
occurrence of
some pre-defined event. In some implementations, mobile device 100 is
assigned its own e-mail address, and messages addressed specifically to mobile
device 100 are automatically redirected to mobile device 100 as they are
received by message server 268.
[0046] To facilitate the wireless communication of messages and
message-related data between mobile device 100 and components of LAN 250,
a number of wireless communications support components 270 may be provided.
In this example implementation, wireless communications support components
270 comprise a message management server 272, for example. Message
management server 272 is used to specifically provide support for the
management of messages, such as e-mail messages, that are to be handled by
mobile devices. Generally, while messages are still stored on message server
268, message management server 272 can be used to control when, if, and how
messages should be sent to mobile device 100. Message management server
272 also facilitates the handling of messages composed on mobile device 100,
which are sent to message server 268 for subsequent delivery.
CA 02477026 2004-08-09
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[0047] For example, message management server 272 may: monitor the
user's "mailbox" (e.g. the message store associated with the user's account on
message server 268) for new e-mail messages; apply user-definable filters to
new messages to determine if and how the messages will be relayed to the
user's mobile device 100; compress and encrypt new messages (e.g. using an
encryption technique such as Data Encryption Standard (DES) or Triple DES)
and push them to mobile device 100 via the shared network infrastructure 224
and wireless network 200; and receive messages composed on mobile device
100 (e.g. encrypted using Triple DES), decrypt and decompress the composed
messages, re-format the composed messages if desired so that they will appear
to have originated from the user's computer 262a, and re-route the composed
messages to message server 268 for delivery.
[0048] Certain properties or restrictions associated with messages that are
to be sent from and/or received by mobile device 100 can be defined (e.g. by
an
administrator in accordance with IT policy) and enforced by message
management server 272. These may include whether mobile device 100 may
receive encrypted and/or signed messages, minimum encryption key sizes,
whether outgoing messages must be encrypted and/or signed, and whether
copies of all secure messages sent from mobile device 100 are to be sent to a
pre-defined copy address, for example.
[0049] Message management server 272 may also be adapted to provide
other control functions, such as only pushing certain message information or
pre-
defined portions (e.g. "blocks") of a message stored on message server 268 to
mobile device 100. For example, when a message is initially retrieved by
mobile
device 100 from message server 268, message management server 272 is
adapted to push only the first part of a message to mobile device 100, with
the
part being of a pre-defined size (e.g. 2 KB). The user can then request more
of
the message, to be delivered in similar-sized blocks by message management
CA 02477026 2004-08-09
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server 272 to mobile device 100, possibly up to a maximum pre-defined message
size.
[0050] Accordingly, message management server 272 facilitates better
control over the type of data and the amount of data that is communicated to
mobile device 100, and can help to minimize potential waste of bandwidth or
other resources.
[0051] It will be understood by persons skilled in the art that message
management server 272 need not be implemented on a separate physical server
in LAN 250 or other network. For example, some or all of the functions
associated with message management server 272 may be integrated with
message server 268, or some other server in LAN 250. Furthermore, LAN 250
may comprise multiple message management servers 272, particularly in variant
implementations where a large number of mobile devices need to be supported.
[0052] Embodiments of the invention relate generally to the processing of
encoded messages, such as e-mail messages that are encrypted and/or signed.
While Simple Mail Transfer Protocol (SMTP), RFC822 headers, and
Multipurpose Internet Mail Extensions (MIME) body parts may be used to define
the format of a typical e-mail message not requiring encoding, Secure/MIME
(S/MIME), a version of the MIME protocol, may be used in the communication of
encoded messages (i.e. in secure messaging applications). S/MIME enables
end-to-end authentication and confidentiality, and protects data integrity and
privacy from the time an originator of a message sends a message until it is
decoded and read by the message recipient. Other known standards and
protocols may be employed to facilitate secure message communication, such as
Pretty Good PrivacyTM (PGP), OpenPGP, and others known in the art.
[0053] Secure messaging protocols such as S/MIME rely on public and
private encryption keys to provide confidentiality and integrity, and on a
Public
Key Infrastructure (PKI) to communicate information that provides
authentication
- .. 3.aRF?*U~W ~S~SNe)Yl&"'4 W ' -' Rk' A".-, A.. ."u9m'xrve
uMmm~:i+uA"rc'++nmmam~re.*rvw....e.,.n...s.~_...-. ._._
CA 02477026 2004-08-09
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and authorization. Data encrypted using a private key of a private key/public
key
pair can only be decrypted using the corresponding public key of the pair, and
vice-versa. Private key information is never made public, whereas public key
information is shared.
[0054] For example, if a sender wishes to send a message to a recipient in
encrypted form, the recipient's public key is used to encrypt a message, which
can then be decrypted only using the recipient's private key. Alternatively,
in
some encoding techniques, a one-time session key is generated and used to
encrypt the body of a message, typically with a symmetric encryption technique
(e.g. Triple DES). The session key is then encrypted using the recipient's
public
key (e.g. with a public key encryption algorithm such as RSA), which can then
be
decrypted only using the recipient's private key. The decrypted session key
can
then be used to decrypt the message body. The message header may be used
to specify the particular encryption scheme that must be used to decrypt the
message. Other encryption techniques based on public key cryptography may
be used in variant implementations. However, in each of these cases, only the
recipient's private key may be used to facilitate decryption of the message,
and in
this way, the confidentiality of messages can be maintained.
[0055] As a further example, a sender may sign a message using a digital
signature. A digital signature is a digest of the message (e.g. a hash of the
message) encrypted using the sender's private key, which can then be appended
to the outgoing message. To verify the signature of the message when received,
the recipient uses the same technique as the sender (e.g. using the same
standard hash algorithm) to obtain a digest of the received message. The
recipient also uses the sender's public key to decrypt the digital signature,
in
order to obtain what should be a matching digest for the received message. If
the digests of the received message do not match, this suggests that either
the
message content was changed during transport and/or the message did not
originate from the sender whose public key was used for verification. By
CA 02477026 2004-08-09
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verifying a digital signature in this way, authentication of the sender and
message
integrity can be maintained.
[0056] An encoded message may be encrypted, signed, or both encrypted
and signed. The authenticity of public keys used in these operations is
validated
using certificates. A certificate is a digital document issued by a
certificate
authority (CA). Certificates are used to authenticate the association between
users and their public keys, and essentially, provides a level of trust in the
authenticity of the users' public keys. Certificates contain information about
the
certificate holder, with certificate contents typically formatted in
accordance with
an accepted standard (e.g. X.509).
[0057] Consider FIG. 5, in which an example certificate chain 300 is
shown. Certificate 310 issued to "John Smith" is an example of a certificate
issued to an individual, which may be referred to as an end entity
certificate. End
entity certificate 310 typically identifies the certificate holder 312 (i.e.
John Smith
in this example) and the issuer of the certificate 314, and includes a digital
signature of the issuer 316 and the certificate holder's public key 318.
Certificate
310 will also typically include other information and attributes that identify
the
certificate holder (e.g. e-mail address, organization name, organizational
unit
name, location, etc.). When the individual composes a message to be sent to a
recipient, it is customary to include that individual's certificate 300 with
the
message.
[0058] For a public key to be trusted, its issuing organization must be
trusted. The relationship between a trusted CA and a user's public key can be
represented by a series of related certificates, also referred to as a
certificate
chain. The certificate chain can be followed to determine the validity of a
certificate.
[0059] For instance, in the example certificate chain 300 shown in FIG. 5,
the recipient of a message purported to be sent by John Smith may wish to
verify
CA 02477026 2010-08-30
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the trust status of certificate 310 attached to the received message. To
verify the
trust status of certificate 310 on a recipient's computing device (e.g.
computer
262a of FIG. 4) for example, the certificate 320 of issuer ABC is obtained,
and
ABC's public key 322 is used to verify that certificate 310 was indeed signed
by
issuer ABC. Certificate 320 may already be stored in a certificate store on
the
computing device, or it may need to be retrieved from a certificate source
(e.g.
LDAP server 284 of FIG. 4 or some other public or private LDAP server). If
certificate 320 is already stored in the recipient's computing device and the
certificate has been designated as trusted by the recipient, then certificate
310 is
considered to be trusted since it chains to a stored, trusted certificate.
[0060] However, in the example shown in FIG. 5, certificate 330 is also
required to verify the trust of certificate 310. Certificate 330 is self-
signed, and is
referred to as a "root certificate". Accordingly, certificate 320 may be
referred to
as an "intermediate certificate" in certificate chain 300; any given
certificate chain
to a root certificate, assuming a chain to the root certificate can be
determined for
a particular end entity certificate, may contain zero, one, or multiple
intermediate
certificates. If certificate 330 is a root certificate issued by a trusted
source (from
a large certificate authority such as Verisign or Entrust, for example), then
certificate 310 may be considered to be trusted since it chains to a trusted
certificate. The implication is that both the sender and the recipient of the
message trust the source of the root certificate 330. If a certificate cannot
be
chained to a trusted certificate, the certificate may be considered to be "not
trusted".
[0061] Certificate servers store information about certificates and lists
identifying certificates that have been revoked. These certificate servers can
be
accessed to obtain certificates and to verify certificate authenticity and
revocation
status. For example, a Lightweight Directory Access Protocol (LDAP) server
may be used to obtain certificates, and an Online Certificate Status Protocol
(OCSP) server may be used to verify certificate revocation status.
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[0062] Standard e-mail security protocols typically facilitate secure
message transmission between non-mobile computing devices (e.g. computers
262a, 262b of FIG. 4; remote desktop devices). Referring again to FIG. 4, in
order that signed messages received from senders may be read from mobile
device 100 and encrypted messages be sent to those senders, mobile device
100 is adapted to store certificates and associated public keys of other
individuals. Certificates stored on a user's computer 262a will typically be
downloaded from computer 262a to mobile device 100 through cradle 264, for
example.
[0063] Certificates stored on computer 262a and downloaded to mobile
device 100 are not limited to certificates associated with individuals but may
also
include certificates issued to CAs, for example. Certain certificates stored
in
computer 262a and/or mobile device 100 can also be explicitly designated as
"trusted" by the user. Accordingly, when a certificate is received by a user
on
mobile device 100, it can be verified on mobile device 100 by matching the
certificate with one stored on mobile device 100 and designated as trusted, or
otherwise determined to be chained to a trusted certificate.
[0064] Mobile device 100 may also be adapted to store the private key of
the public key/private key pair associated with the user, so that the user of
mobile
device 100 can sign outgoing messages composed on mobile device 100, and
decrypt messages sent to the user encrypted with the user's public key. The
private key may be downloaded to mobile device 100 from the user's computer
262a through cradle 264, for example. The private key is preferably exchanged
between the computer 262a and mobile device 100 so that the user may share
one identity and one method for accessing messages.
[0065] User computers 262a, 262b can obtain certificates from a number
of sources, for storage on computers 262a, 262b and/or mobile devices (e.g.
mobile device 100). These certificate sources may be private (e.g. dedicated
for
use within an organization) or public, may reside locally or remotely, and may
be
CA 02477026 2004-08-09
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accessible from within an organization's private network or through the
Internet,
for example. In the example shown in FIG. 4, multiple PKI servers 280
associated with the organization reside on LAN 250. PKI servers 280 include a
CA server 282 for issuing certificates, an LDAP server 284 used to search for
and download certificates (e.g. for individuals within the organization), and
an
OCSP server 286 used to verify the revocation status of certificates.
[0066] Certificates may be retrieved from LDAP server 284 by a user
computer 262a, for example, to be downloaded to mobile device 100 via cradle
264. However, in a variant implementation, LDAP server 284 may be accessed
directly (i.e. "over the air" in this context) by mobile device 100, and
mobile
device 100 may search for and retrieve individual certificates through a
mobile
data server 288. Similarly, mobile data server 288 may be adapted to allow
mobile device 100 to directly query OCSP server 286 to verify the revocation
status of certificates.
[0067] In variant implementations, only selected PKI servers 280 may be
made accessible to mobile devices (e.g. allowing certificates to be downloaded
only from a user's computer 262a, 262b, while allowing the revocation status
of
certificates to be checked from mobile device 100).
[0068] In variant implementations, certain PKI servers 280 may be made
accessible only to mobile devices registered to particular users, as specified
by
an IT administrator, possibly in accordance with an IT policy, for example.
[0069] Other sources of certificates [not shown] may include a Windows
certificate store, another secure certificate store on or outside LAN 250, and
smart cards, for example.
[0070] Referring now to FIG. 6, a block diagram illustrating components of
an example of an encoded message, as may be received by a message server
(e.g. message server 268 of FIG. 4), is shown generally as 350. Encoded
message 350 typically includes one or more of the following: a header portion
CA 02477026 2004-08-09
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352, an encoded body portion 354, optionally one or more encoded attachments
356, one or more encrypted session keys 358, and signature and signature-
related information 360. For example, header portion 352 typically includes
addressing information such as "To", "From", and "CC" addresses, and may also
include message length indicators, and sender encryption and signature scheme
identifiers, for example. Actual message content normally includes a message
body or data portion 354 and possibly one or more attachments 356, which may
be encrypted by the sender using a session key. If a session key was used, it
is
typically encrypted for each intended recipient using the respective public
key for
each recipient, and included in the message at 358. If the message was signed,
a signature and signature-related information 360 are also included. This may
include the sender's certificate, for example.
[0071] The format for an encoded message as shown in FIG. 6 is provided
by way of example only, and persons skilled in the art will understand that
embodiments of the invention will be applicable to encoded messages of other
formats. Depending on the specific messaging scheme used, components of an
encoded message may appear in a different order than shown in FIG. 6, and an
encoded message may include fewer, additional, or different components, which
may depend on whether the encoded message is encrypted, signed or both.
[0072] Embodiments of the invention are generally directed to a system
and method for searching and retrieving certificates that automates at least
some
of the tasks typically performed manually by users in known techniques for
searching certificates, and provide means for large numbers of certificates to
be
retrieved from one or more certificate servers.
[0073] Many certificate servers (e.g. LDAP servers, such as LDAP server
284 of FIG. 4) are configured to impose limits on the number of certificates
that
will be located on and retrieved from the server in the processing of a given
search query. For example, this may be done to prevent a search from
inadvertently returning too many results if the query used was, perhaps
CA 02477026 2004-08-09
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unintentionally, defined too broadly. Typically, a search is performed on a
certificate server to locate a few, select certificates for specific
individuals.
[0074] However, in certain situations, it may be desirable to obtain a large
number, if not all of the certificates, particularly end entity certificates,
which are
stored on one or more specific certificate servers. For example, many
organizations set up their own LDAP servers to store certificates issued to
people
within the organization who are able (or set up) to send and receive encoded
messages. If the organization is not too large, some individuals within the
organization may wish to download most or all of the end entity certificates
on the
organization's LDAP server, and store them on that individual's computing
device
for future use. In the event that a particular certificate is subsequently
needed to
encode or decode a message exchanged (or to be exchanged) with another
individual in the same organization, it is likely that the requisite
certificate has
already been retrieved and stored, and a manual search for and retrieval of
the
certificate from the LDAP server may not be required.
[0075] In one embodiment of the invention, a certificate synchronization
application is provided on a user's computing device. The certificate
synchronization application is programmed to allow users to initiate
certificate
searches of one or more certificate servers and retrieve large numbers of
certificates, if not all of the certificates, on those certificate servers in
accordance
with one of the methods in an embodiment of the invention, as may be described
with reference to the remaining Figures.
[0076] In one embodiment of the invention, the certificate synchronization
application executes and resides on a user's desktop computer (e.g. computer
262a of FIG. 4) to which a cradle (e.g. cradle 264 of FIG. 4) for a mobile
device
(e.g. mobile device 100 of FIG. 4) is connected. However, in variant
embodiments of the invention, the certificate synchronization application may
execute and reside on a desktop computer not equipped with a cradle for a
mobile device, or on some other computing device. For example, the certificate
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synchronization application may execute and reside on a mobile device, which
may have direct access to certificate servers (e.g. through mobile data server
288 of FIG. 4). By way of further example, the certificate synchronization
application need not be executing on the same computing device to which
certificates would typically be downloaded. For example, the certificate
synchronization application may execute on a central server, such as a message
management server (e.g. message management server 272 of FIG. 4) or
message server (e.g. message server 268 of FIG. 4), for example. Moreover,
the certificate synchronization application need not be a stand-alone
application,
and the functions of the certificate synchronization application described
herein
may be integrated with the functions of some other application, residing and
executing on a computing device such as a desktop computer, a mobile device, a
message management server, a message server, or some other computing
device.
[0077] Referring to FIG. 7A, a flowchart illustrating steps in a method of
searching and retrieving certificates in an embodiment of the invention is
shown
generally as 400. The method facilitates at least partial automation of a pre-
loading of certificates, to minimize the need for a user to manually search
for a
certificate for individuals whose certificates are stored on specific
certificate
servers. These certificate servers may be maintained by an organization to
which the user belongs, for example.
[0078] In one embodiment of the invention, at least some of the steps of
the method are performed by a certificate synchronization application that
executes and resides on a desktop computer. In variant embodiments, the
certificate synchronization application may be residing and executing on a
computing device such as a mobile device, a message management server, a
message server, or some other computing device.
[0079] At step 410, one or more certificate servers (e.g. LDAP server 284
of FIG. 4) that will be used for certificate searches are configured for
access. Of
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those configured certificate servers, one or more certificate servers may be
designated for certificate searching in accordance with an embodiment of the
invention.
[0080] Typically, information required to configure a certificate server may
include, for example, a host name, a host address or uniform resource locator
(URL), a port number (e.g. for LDAP servers), a default base query, a query
limit
(e.g. user-defined, independent of the limit that the server itself may
impose),
and/or an indication of whether certificate information is to be compressed
for
transmission. In one implementation, such configuration information can be
input
by a user, and default values for certain inputs may be set in the certificate
synchronization application. In other implementations, such configuration
information may already be pre-defined in the certificate synchronization
application, possibly by an IT administrator in accordance with an IT policy.
Still
other implementations may permit some configuration information to be input or
modified by users, while not permitting other configuration information to be
user-
modified.
[0081] Similarly, in one implementation, the certificate synchronization
application may permit users to manually designate specific certificate
servers
that will be queried and searched in accordance with an embodiment of the
invention. In other implementations, the certificate synchronization
application
may automatically designate certain pre-identified specific certificate
servers to
be searched, possibly as directed by an IT administrator in accordance with an
IT
policy. Still other implementations may permit some degree of user
configuration, by allowing a user to designate specific certificate servers
but only
from a set defined by an IT administrator, in accordance with an IT policy,
for
example.
[0082] At step 420, a request is received by the certificate synchronization
application from the user to initiate a search for all certificates in the
servers
designated at step 410.
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[0083] At step 430, the certificate synchronization application searches for
certificates by automatically querying a designated certificate server,
attempting
to locate and retrieve all of the certificates stored on each server. For
example,
certain certificate servers will accept blank queries or queries employing
some
"wild card" type search indicator, and return all certificates stored on the
server.
[0084] In this embodiment of the invention, the queries are defined to
return end entity certificates only. However, in variant embodiments of the
invention, the queries may be defined to return other types of certificates
(e.g.
root and/or intermediate certificates issued to CAs), or some combination of
different types of certificates.
[0085] Depending on the particular certificate server, if all of the
certificates on the certificate server cannot be successfully located and
retrieved,
possibly due to a limit on the number of potential search results being
exceeded
(also referred to herein in the specification and claims as a "quota"), the
certificate server may terminate the search and issue an error indicator, and
return no results or return a limited number of results.
[0086] If some, but not all certificates could be located and retrieved at
step 430 as determined at step 440, these certificates (i.e. the truncated
search
results) may be discarded at step 450 to avoid potential duplication that
might
arise as a result of further searching. However, step 450 is optional, and the
removal of any duplicates may be deferred, after searching of the designated
certificate server has been completed, for example.
[0087] If at step 440, it is determined that not all certificates stored on
the
designated server searched at step 430 were successfully located and
retrieved,
a "divide-and-conquer" approach may then be employed. Such an approach to
the searching of certificates on certificate servers may not have been
considered
by persons skilled in the art, since quotas on the number of search results
that
can be obtained from a search of a certificate server are typically
established
CA 02477026 2004-08-09
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specifically to prevent or at least impede such a mass (or "bulk") downloading
of
certificates. Accordingly, a divide-and-conquer technique is used to overcome
the search limitations imposed by such quotas.
[0088] Generally, algorithms that follow a divide-and-conquer approach
break a particular problem into several subproblems that are similar to the
original problem but smaller in size, solve the subproblems recursively, and
then
combine these solutions to create a solution to the original problem. More
specifically, the divide-and-conquer paradigm generally involves three steps
at
each level of the recursion:
= divide the problem into a number of subproblems;
= solve each of the subproblems recursively ("conquer"); if the
subproblem sizes are small enough, however, then the subproblems
can be solved in a straightforward manner; and
= combine the solutions to the subproblems to obtain the solution for the
original problem.
[0089] In the context of embodiments of the invention, the problem to be
solved relates to the searching and retrieval of all of the certificates from
the
designated certificate server(s). If at step 440, it is determined that not
all
certificates stored on the designated certificate server searched at step 430
were
successfully located and retrieved, the search is divided into two or more
narrower searches ("subsearches") at step 460. The subsearches are defined so
that the results of the two subsearches can be combined to obtain what would
have resulted from the search had the search been successful in the first
instance.
[0090] The subsearches are then performed recursively at step 470
through corresponding queries of the designated certificate server made by the
certificate synchronization application; if a particular subsearch does not
successfully locate all of the certificates associated with that subsearch
(e.g. due
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to a search quota being exceeded), that subsearch can be divided into a
further
level of subsearches. If any of the subsearches at that further level are not
successful, those subsearches can each be divided into yet another level of
subsearches, and so on, until search results for each subsearch is obtained,
which can then be combined to produce the overall search results.
[0091] In a variant embodiment of the invention, a limit on the number of
levels of recursion that may be permitted with respect to the search may be
defined and enforced by the certificate synchronization application. This
recursion level limit may be established by an IT administrator, in accordance
with an IT policy, for example.
[0092] The form of the subsearches into which a search may be divided
can differ in different implementations. For example, if a certificate server
permits range-type queries, a search of all certificates may be divided into a
first
subsearch for certificates issued to individuals with a last name beginning
with a
letter from A-M and a second subsearch for certificates issued to individuals
with
a last name beginning with N-Z; each of these subsearches, if unsuccessful,
may
be further divided into smaller subsearches (e.g. A-M -> A-G + H-M, N-Z -> N-S
+ T-Z), and so on. Any truncated results of unsuccessful subsearches may be
optionally discarded. For any given search or subsearch, the search or
subsearch can be divided into two, three, or more subsearches at any given
level
of recursion, and the scopes of the subsearches within a particular level or
between different levels of recursion can differ. Subsearches may be based on
any of a number of appropriate attributes, which can be used to query a given
certificate server, including last names, first names, e-mail addresses,
employee
numbers, and organizational unit identifiers, for example. It will be
understood by
persons skilled in the art that many different variations of divide-and-
conquer
type algorithms may be employed without departing from the scope of the
invention.
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[0093] At step 480, if not all designated certificate servers have been
searched, searching is performed on a designated certificate server that has
not
yet been searched. Accordingly, steps of method 400 may be repeated from
step 430 until all designated certificate servers have been searched.
[0094] At step 490, located certificates resulting from the searches of the
designated certificate servers are downloaded to the computing device. In this
embodiment, these certificates are stored temporarily on the computing device,
and only a subset of certificates as selected by a user is stored for future
use.
This allows the user to filter the search results and discard unwanted or
irrelevant
certificates. However, in a variant implementation, all located certificates
may be
automatically stored for future use on the computing device at step 490
without
being filtered by the user. In this case, the remaining steps of method 400
would
not be performed.
[0095] At step 500, a list of located certificates downloaded to the
computing device at step 490 is displayed to the user.
[0096] At step 510, a subset of certificates may be selected by the user
from the list displayed at step 500, to be stored for future use.
[0097] At step 520, the certificates selected at step 510 are stored in a
certificate store on the computing device.
[0098] In a variant embodiment of the invention, the certificates selected at
step 510 may be stored on a (e.g. desktop) computer, and at least a subset of
those selected certificates may then be downloaded to a mobile device for
storage in a certificate store on the mobile device. Certificate downloading
to the
mobile device can be facilitated through a physical coupling to the computing
device (e.g. through cradle 264 of FIG. 4) or through a wireless connection,
for
example. In another variant embodiment of the invention, the selected
certificates or a subset thereof may be stored in a certificate store on the
mobile
device, but not in a certificate store on the computing device.
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[0099] In a variant embodiment of the invention, method 400 further
comprises a step of filtering out duplicate certificates that have been
downloaded
to the computing device. The list of located certificates displayed at step
500
may be generated to reflect the filtered results.
[00101] Referring to FIG. 7B, a flowchart illustrating steps in a method of
searching and retrieving certificates in another embodiment of the invention
is
shown generally as 400b. Method 400b is similar to method 400, except that
this
embodiment of the invention is directed to a specific algorithm used in the
certificate search.
[00102] If at step 440, it is determined that not all certificates stored on
the
designated certificate server searched at step 430 were successfully located
and
retrieved, the search is divided into multiple subsearches at step 460b.
Specifically, the search is divided into a subsearch for certificates issued
to
individuals with names beginning with "A", a subsearch for certificates issued
to
individuals with names beginning with "B", a subsearch for certificates issued
to
individuals with names beginning with "C", and so on, so that subsearches are
performed for all names beginning with letters "A" through "Z". Additional
subsearches or modification of the queries used may be necessary to
accommodate situations where the data may be case-sensitive. Additional
subsearches may also be performed to search for certificates having names that
may begin with numeric or special characters. In one embodiment of the
invention, the last name attribute may be searched for this purpose, but
alternatively, other name attributes (e.g. first name) may instead be used. In
variant embodiments of the invention, other fields other than name fields may
be
similarly searched.
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[00103] The subsearches are then performed recursively at step 470
through corresponding queries of the designated certificate server. For
example,
if the subsearch for certificates issued to individuals with names beginning
with
"A" was not successful, possibly due to a limit on the number of potential
search
results being exceeded, the certificate synchronization application will then
divide
this subsearch into further subsearches to be performed. The subsearch can be
divided into a subsearch for certificates issued to individuals with names
beginning with "AA", a subsearch for certificates issued to individuals with
names
beginning with "AB", a subsearch for certificates issued to individuals with
names
beginning with "AC", and so on, so that subsearches are performed for all
names
beginning with letters "AA" through "AZ". Each of these subsearches, if
unsuccessful, may be divided into further subsearches, extending each prefix
by
a letter at each level of recursion. Any truncated results of unsuccessful
subsearches may be optionally discarded. A maximum limit on the prefix length
(and thus the number of levels of recursion) may be defined and enforced by
the
certificate synchronization application. This limit may be established by an
IT
administrator, in accordance with an IT policy, for example.
[00104] With respect to methods of searching and retrieving certificates in
embodiments of the invention, subsearches may be performed sequentially or
concurrently, depending on the particular implementation. The ability to
perform
subsearches concurrently may depend on the particular computing device on
which the certificate synchronization application executes and/or on the
ability of
a given certificate server to handle multiple queries from the application
simultaneously.
[00105] The steps of a method of searching and retrieving certificates in
embodiments of the invention may be provided as executable software
instructions stored on computer-readable media, which may include
transmission-type media.
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[00106] The invention has been described with regard to a number of
embodiments. However, it will be understood by persons skilled in the art that
other variants and modifications may be made without departing from the scope
of the invention as defined in the claims appended hereto.
