Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR EXCHANGING ENCRYPTION KEYS BETWEEN
A MOBILE DEVICE AND A PERIPHERAL DEVICE
Relevant Field
[0001] Embodiments of the invention relate generally to wireless
peripheral devices for use with computing devices. More specifically, at least
some of the embodiments described herein relate to a system and method for
securely exchanging an encryption key between a wireless peripheral device and
a mobile device.
Background
[0002] Bluetooth is a known, short-range wireless technology used to
connect a wide range of devices. It is a globally available standard that is,
currently, widely supported. Bluetooth technology provides a number of
security
features, including personal identification number (PIN) authentication and
the
encryption of data transmitted between paired devices. After Bluetooth-capable
devices identify themselves to each other, a PIN code is used the first time
they
connect. The PIN is a four or more digit alphanumeric code that is either
fixed for
or temporarily associated with a device, for the purpose of pairing with
another
device to which a Bluetooth wireless connection is desired.
[0003] Some experts believe that Bluetooth connections, for which security
depends on the secure pairing of devices based on the PIN, are inherently
insecure, particularly when the length of the PIN (e.g. typically four digits)
is
small. Some organizations that would require potentially sensitive data to be
communicated between a mobile device and a wireless peripheral device may
not consider the level of security afforded by the current Bluetooth standard
alone to be sufficient.
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Summary
[0004] In one broad aspect, there is provided a method of exchanging an
encryption key between a computing device and a wireless peripheral device,
the
method comprising the steps of: generating an encryption key at one of the
computing device and the peripheral device; outputting data associated with
the
encryption key to a user at the one device; receiving the data associated with
the
encryption key input by the user at the other of the computing device and the
peripheral device; recovering the encryption key at the other device from the
data
associated with the encryption key input by the user; and transmitting data
encrypted with the encryption key over a wireless connection between the
computing device and the peripheral device, the wireless connection
established
in accordance with a wireless protocol; wherein the data associated with the
encryption key is non-derivable from the data transmitted between the
computing
device and the peripheral device at the transmitting step.
Brief Description of the Drawings
[0005] For a better understanding of embodiments of the systems and
methods described herein, and to show more clearly how they may be carried
into effect, reference will 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. 4A is a block diagram illustrating components of a system comprising a
mobile device and a wireless peripheral device for use therewith;
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FIG. 4B is a flowchart illustrating steps of a method of exchanging an
encryption
key between the mobile device and the wireless peripheral device of the system
shown in FIG. 4A;
FIG. 5A is a block diagram illustrating components of the system shown in FIG.
4A where the wireless peripheral device is a keyboard;
FIG. 5B is a flowchart illustrating steps of a method of exchanging an
encryption
key between the mobile device and the keyboard of the system shown in FIG.
5A;
FIG. 6A is a block diagram illustrating components of the system shown in FIG.
4A where the wireless peripheral device is a printer;
FIG. 6B is a flowchart illustrating steps of a method of exchanging an
encryption
key between the mobile device and the printer of the system shown in FIG. 6A;
and
FIG. 7 is a flowchart illustrating steps of a method of exchanging an
encryption
key between the mobile device and the wireless peripheral device of the system
shown in FIG. 4A, in a variant embodiment.
Detailed Description
[0006] Embodiments of the systems and methods described herein relate
generally to wireless peripheral devices for use with computing devices, and
in
respect of at least one embodiment, more specifically to a system and method
for
securely exchanging an encryption key between a wireless peripheral device and
a mobile device. The encryption key, once made available at both the wireless
peripheral device and the mobile device, may be subsequently used to encrypt
and/or decrypt data transmitted between the two devices.
[0007] In one broad aspect, there is provided a method of exchanging an
encryption key between a computing device and a wireless peripheral device,
the
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method comprising the steps of: generating an encryption key at one of the
computing device and the peripheral device; outputting data associated with
the
encryption key to a user at the one device; receiving the data associated with
the
encryption key input by the user at the other of the computing device and the
peripheral device; recovering the encryption key at the other device from the
data
associated with the encryption key input by the user; and transmitting data
encrypted with the encryption key over a wireless connection between the
computing device and the peripheral device, the wireless connection
established
in accordance with a wireless protocol; wherein the data associated with the
encryption key is non-derivable from the data transmitted between the
computing
device and the peripheral device at the transmitting step.
[0008] In another broad aspect, there is provided a method of exchanging
an encryption key between a computing device and a wireless keyboard, the
method comprising the steps of: generating an encryption key at the computing
device; outputting data associated with the encryption key to a user at the
computing device; receiving the data associated with the encryption key input
by
the user at the keyboard; recovering the encryption key at the keyboard from
the
data associated with the encryption key input by the user; and transmitting
data
encrypted with the encryption key over a wireless connection between the
computing device and the keyboard, the wireless connection established in
accordance with a wireless protocol; wherein the data associated with the
encryption key is non-derivable from the data transmitted between the
computing
device and the peripheral device at the transmitting step.
[0009] In another broad aspect, there is provided a method of exchanging
an encryption key between a computing device and a wireless printer, the
method comprising the steps of: generating an encryption key at the printer;
outputting data associated with the encryption key to a user at the printer;
receiving the data associated with the encryption key input by the user at the
computing device; recovering the encryption key at the computing device from
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the data associated with the encryption key input by the user; and
transmitting
data encrypted with the encryption key over a wireless connection between the
computing device and the printer, the wireless connection established in
accordance with a wireless protocol; wherein the data associated with the
encryption key is non-derivable from the data transmitted between the
computing
device and the peripheral device at the transmitting step.
[0010] In exemplary embodiments, the computing device is a mobile
device.
[0011] Features of these and other aspects, and of a number of
embodiments of systems and methods are described below.
[0012] The description of some embodiments of the systems and methods
described herein make reference to a mobile device, also known in the art as a
mobile station. A mobile device is a two-way communication device with
advanced data communication capabilities having the capability to communicate
with other computer systems. 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.
[0013] 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.
[0014] 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
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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
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.
[0015] 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
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Radio Network. Examples of older voice-centric data networks include Personal
Communication Systems (PCS) networks like GSM and Time Division Multiple
Access (TDMA) systems.
[0016] Other network communication technologies that may be employed
include, for example, Integrated Digital Enhanced Network (iDENT""), Evolution-
Data Optimized (EV-DO), and High Speed Downlink Packet Access (HSDPA).
[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
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
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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 to 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.
[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
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task items. A PIM application has the ability to send and receive data items
via
wireless network 200. PIM data items may be seamiessly 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
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, short-range communication
subsystem 122 may include an infrared device and associated circuits and
components for short-range communication. The short-range communication
subsystem 122 can be used to communicate with aVVireless Personal Area
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network (WPAN). In some cases, the short-range communications subsystem
122 can comprise a Bluetooth radio, a ZigBee device, a Wireless USB (WUSB)
device, and/or an Ultra-Wideband (UWB) radio, for example. Examples of short
range communication standards include standards developed by the Infrared
Data Association (IrDA), Bluetooth, ZigBee, WUSB, UWB, and the 802.11 and
802.15 families 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 I/O 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.
[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
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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 (A/D) 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
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.
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[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
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
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referred to as a"celP'. 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
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 require 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
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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
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
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and the IP address returned to the IP address pool managed by DHCP server
220.
[0037] At least some of the embodiments described herein are directed to
a system and method for securely exchanging an encryption key between a
wireless peripheral device and a mobile device.
[0038] Some experts believe that connections between Bluetooth devices,
of which security depends on the secure pairing of the devices based on a PIN,
are inherently insecure, particularly where the length of the PIN (e.g.
typically
four digits) is small. Furthermore, security may also be compromised if the
pairing process is not performed in private.
[0039] Accordingly, in at least one embodiment, means for providing
additional security for data being transmitted across a wireless connection
that
has been established using a known wireless protocol (e.g. Bluetooth) is
described herein. More specifically, embodiments of a system and method for
exchanging an encryption key between a mobile device and a wireless peripheral
device are described herein, where the encryption key can be subsequently used
to encrypt and/or decrypt data transmitted between the two devices across the
established wireless connection.
[0040] In these embodiments, the encryption key that is exchanged
between the mobile device and the wireless peripheral device is unrelated to
(i.e.
not derivable from) any PIN that may be used to pair two (e.g. Bluetooth-
enabled) devices, for example. This provides additional security, as a brute
force
recovery of the PIN would not aid any malicious attempt to uncover the
exchanged encryption key, which could then be used to decrypt potentially
sensitive data that is transmitted between the two devices.
[0041] Furthermore, the security associated with the subsequent use of an
exchanged encryption key is provided in addition to any security that is
inherent
in the underlying established wireless connection. For example, depending on
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the security mode for Bluetooth access that has been enabled between two
devices, data being transmitted across a Bluetooth connection between the two
devices can be encrypted as the Bluetooth standard provides for data
encryption
capability. However, the additional security afforded by the use of the
encryption
key exchanged in accordance with an embodiment described herein would be
provided to data transmitted over the Bluetooth connection, whether the built-
in
Bluetooth data encryption capability has been enabled or not.
[0042] By allowing additional security to be introduced in a manner that is
independent of the protocol used to establish the underlying (e.g. Bluetooth)
wireless connection, greater flexibility may be provided. For example, it may
be
easier to modify existing devices that are already capable of establishing
wireless
connections in accordance with a known protocol, in order to provide the
additional security. As a further example, once two devices are paired or
otherwise connected, new encryption keys that may be used to provide the
additional security can generally be exchanged at any desired time, and at any
desired frequency, between the devices.
[0043] In exemplary embodiments, the encryption key used to provide
additional security is a key that is used to encrypt and decrypt data in
accordance
with a symmetric encryption technique, such as the Advanced Encryption
Standard (AES), Data Encryption Standard (DES), or Triple DES (3DES), for
example. In order for both the mobile device and the wireless peripheral
device
to be capable of encrypting and decrypting the data that each device is to
transmit to the other over the established (e.g. Bluetooth) wireless
connection,
there is a need for a secure means to exchange the encryption key to be used
between the two devices.
[0044] It will be understood by persons skilled in the art that the act of
exchanging an encryption key need not involve the transmission of the actual
encryption key itself from one device to the other. It will also be understood
that
it is not necessary that an actual encryption key be initially generated at
only one
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device and then subsequently transferred to the other device in order to
constitute an "exchange". It is sufficient that the encryption key to be used
is
derived at or otherwise becomes known to each device, through the processing
of some data that is shared between the two devices. In that case, a key
"exchange" is deemed to have occurred.
[0045] Referring to FIGS. 4A and 4B, a block diagram illustrating
components of a system comprising a mobile device and a wireless peripheral
device for use therewith, and a flowchart illustrating steps of a method of
exchanging an encryption key between the mobile device and the wireless
peripheral device, in at least one embodiment, are shown generally as 300 and
330 respectively.
[0046] In FIG. 4A, a system 300 comprising a mobile device 100 coupled
to a peripheral device 310 via a wireless connection 320 is shown. In
exemplary
embodiments, mobile device 100 comprises a short-range communications
subsystem (e.g. 122 of FIG. 1) to facilitate wireless communication with
peripheral device 310 over wireless connection 320. Wireless connection 320
may be a Bluetooth connection, for example.
[0047] In one embodiment, peripheral device 310 is a device that provides
keyboard or keypad input capabilities, as described in greater detail below
with
reference to FIGS. 5A and 5B. In another embodiment, peripheral device 310 is
a device that provides printing capabilities, as described in greater detail
below
with reference to FIGS. 6A and 6B. In variant embodiments, peripheral device
310 will be some other device with either input and/or output capabilities.
[0048] Referring now to FIG. 4B, method 330 commences with the
establishment of the wireless connection 320 between the mobile device 100 and
the peripheral device 310 in accordance with a known wireless protocol (e.g.
Bluetooth), at step 332.
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[0049] If wireless connection 320 is a Bluetooth connection, step 332 may
comprise configuring both devices so that they are made visible for pairing,
placing both devices into a pairing mode, and completing a pairing process in
known manner. In the pairing process, a PIN code generated by one device or
otherwise fixedly associated with the one device is entered into the other
device
via a user interface, and the two devices subsequently validate each other.
[0050] In exemplary embodiments, a software application that executes on
mobile device 100 (e.g. by microprocessor 102 of FIG. 1) is programmed to
perform at least a first subset of the steps of method 330, and a software
application that executes on peripheral device 310 (e.g. as firmware of
peripheral
device 310) is programmed to perform at least a second subset of the steps of
method 330. In variant embodiments, the instructions to perform some or all of
the steps of method 330 may be embedded in hardware.
[0051] At step 334, both the mobile device 100 and the peripheral device
310 are placed into an "additional security" operational mode, which indicates
that data transmissions are to be encrypted with an encryption key that is to
be
exchanged between the two devices as described herein.
[0052] Mobile device 100 may be placed into the additional security
operational mode, for example, in response to a user request (e.g. the user
manually selects a corresponding configuration option at the mobile device
100),
automatically after pairing has been completed at step 332, or automatically
in
accordance with a pre-defined schedule. The manner in which mobile device
100 can be placed into the additional security operational mode may be
reflected
in configuration settings on mobile device 100. In variant embodiments, the
values of the configuration settings may be set in accordance with a security
policy ("IT Policy") governing the use of mobile device 100.
[0053] Similarly, peripheral device 310 may be placed into the additional
security operational mode, for example, in response to a user request (e.g.
the
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user manually operates a button on the peripheral device in a pre-specified
manner), automatically after pairing has been completed at step 332, or
automatically in accordance with a pre-defined schedule.
[0054] Placing both devices into the additional security operational mode
may require that action be independently taken at each device. Alternatively,
a
first of two devices may be placed into the additional security operational
mode
(either automatically or in response to user input), which subsequently
triggers
the transmission of a command to the second of the two devices over the
wireless connection 320. In the latter case, placement of the second device
into
the additional security operational mode is performed automatically upon
receipt
of the command at the second device from the first device.
[0055] At step 336, an encryption key is generated at one of the mobile
device 100 and the peripheral device 310, in accordance with a key-generating
algorithm. For example, the key-generating algorithm may produce a random
128-bit, 196-bit, or 256-bit number. The one device at which the encryption
key
is generated at this step needs to be capable of providing output to a user,
while
the other of the two devices must be capable of receiving input from the user.
The generated encryption key is then typically stored at the one device [step
not
explicitly shown].
[0056] Optionally, at step 338, the encryption key generated at step 338 is
converted into new data, preferably in a more user-friendly format, using a
key-
conversion algorithm. The key-conversion algorithm that is used must allow the
encryption key to be recoverable from the new data (with possibly some other
data). Therefore, for example, a hashing function would generally be
inappropriate for performing the conversion at this step.
[0057] The format that may be employed for the new data may depend on
the input capabilities of the other of the mobile device 100 and the
peripheral
device 310. For instance, an encryption key may be converted into a shorter
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alphanumeric string, if the other device is capable of receiving such strings
as
input.
[0058] In one embodiment, the key-conversion algorithm simply converts a
binary key into a hexadecimal number, and produces the hexadecimal number
as the string, for example.
[0059] At step 340, data is output to a user at the one device where the
encryption key was generated at step 336. Where step 338 is not performed, the
data output at step 340 might comprise the actual encryption key. However,
more typically, the data output at step 340 will comprise the new data
generated
from the conversion of the encryption key as performed at step 338.
[0060] The data output to the user at step 340 might be, for example,
shown in a display (e.g. a liquid crystal display (LCD)), written to a
physical
medium (e.g. paper, disk), provided in an audio format (e.g. peripheral device
310 may be a headset or speaker, and the headset or speaker could further
convert a string or number into speech to be output to the user), or presented
on
a touch-based device (e.g. Braille pad). Additional instructions and other
information to be considered by the user may also be provided with the data
that
is output at this step.
[0061] In operation, after the data is output to a user at step 340 at one of
the mobile device 100 and the peripheral device 310, the user will input the
data
at the other of the two devices, via a user interface provided at the other
device.
The data is not transmitted over the wireless connection 320.
[0062] The data input by the user is received at the other device, as shown
at step 342. For example, step 342 may comprise receiving an alphanumeric
string that was generated by conversion at step 338, as user input.
[0063] At step 344, the encryption key (originally generated at step 336) is
recovered at the device receiving the data input at step 342, and subsequently
stored at that device [storing step not explicitly shown]. This may require
the
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application of an appropriate key recovery technique associated with the key-
conversion algorithm employed at step 338, if step 338 was performed.
Depending on the key-conversion algorithm being employed, recovering the
encryption key may also require processing other data (e.g. which may be pre-
stored or otherwise provided to the device) in addition to the data received
from
the user at step 342.
[0064] Accordingly, after step 344 is performed, the encryption key is
available at both mobile device 100 and peripheral device 310. Completion of
steps 336 to 344 constitutes a secure exchange of the encryption key between
the two devices.
[0065] With the encryption key now available at both devices, data may be
transmitted between the devices as shown at step 346, where the transmissions
are encrypted using the encryption key in accordance with a data encryption
algorithm (e.g. AES, DES, 3DES). Transmitted data received by a device can
then be subsequently decrypted using the same encryption key [step not
explicitly shown].
[0066] The out-of-band exchange of data output at one device with the
other device will prevent hackers who surreptitiously monitor wireless
communications from intercepting the data over the wireless connection and
recovering the encryption key.
[0067] In view of the additional security provided by embodiments of
method 330, it will be understood that in respect of Bluetooth connections,
even if
a hacker were able to pair with one of two Bluetooth devices and masquerade as
the other device, the hacker would not have access to the encryption key
necessary to decrypt the transmissions it receives. Moreover, the encryption
key
exchanged in accordance with embodiments described herein could not be
derived from a PIN even if the hacker manages to uncover the PIN.
Furthermore, unlike a PIN used to pair Bluetooth devices that might be
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maliciously uncovered by the hacker (particularly when the length of the PIN
is
small), there is no data that is exchanged over the established wireless
connection 320 when encrypted with an encryption key of sufficient length,
that
could effectively be used to derive the data output at step 340 at one device
to be
shared out-of-band with the other device. Effectively, the data output at step
340
is non-derivable from the encrypted data transmitted between the two devices.
The data output at step 340 is used to derive the encryption key, and not for
the
purposes of pairing two devices. Accordingly, additional security is provided.
[0068] It will be understood by persons skilled in the art that some of the
steps of method 330 may be repeated. For example, new keys may be
exchanged between the two devices (e.g. by repeating steps 336 to 344) in
accordance with a pre-defined schedule, at a certain frequency, or as
otherwise
desired, automatically and/or in response to a user request. This flexibility
may
provide additional security without requiring a new wireless connection to be
established or a pairing process to be repeated.
[0069] Furthermore, in variant embodiments, the same data may be output
at one device (at step 340) to be input by a user at multiple other devices.
The
same encryption key may be recovered from this data at each of the devices
sharing the data, and used to encrypt and decrypt data transmitted between any
subset of these devices when connected, if desired.
[0070] Details of embodiments of method 330 have been provided above
with reference to a mobile device and a general peripheral device. Additional
details of the method will now be provided in the description of FIGS. 5B and
6B
that follows, where the peripheral device is more specifically a wireless
keyboard
310a as shown in FIG. 5A, and where the peripheral device is more specifically
a
peripheral output device such as a wireless printer 310b as shown in FIG. 6A
respectively. It will be understood, however, that method 330 may be
implemented in respect of other peripheral devices in variant embodiments.
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[0071] For example, in one variant embodiment, peripheral device 310
may be a headset, and data is output to the user at step 340 at the headset
(e.g.
either as audio/speech or via a display on the headset) to be entered by the
user
on the mobile device, received by the mobile device at step 342.
[0072] It will be understood that there may be particular benefits
associated with embodiments where the data is output (at step 340) at the
peripheral device, and the data is input at the mobile device (received at
step
342). In these embodiments, the data to be shared is first generated at the
peripheral device, and not at the mobile device. In the past, prior art
peripheral
output devices were not adapted to perform tasks related to generating data
associated with encryption keys. This may be attributed to the fact that the
peripheral devices are generally not expected to perform such processing
tasks.
Furthermore, peripheral devices capable of outputting data to a user (e.g.
printers, headsets) are often considered to be passive devices compared to the
mobile device or other computing device to which they may be connected.
[0073] Accordingly, greater flexibility may be provided where the data
output at step 340 is output at the peripheral device. For example, some of
the
processing tasks required in the exchange of encryption keys are diverted to
the
peripheral device, potentially conserving resources at the computing device
connected to the peripheral device, which may be particularly beneficial when
the
computing device is a mobile device. Furthermore, the user may receive the
output data from the peripheral device and enter it into the mobile device or
other
computing device, prior to when additional security is desired, at the
convenience
of the user. This may, for instance, permit more efficient configuration of a
system in which keys are to be exchanged between multiple peripheral devices
and the mobile device or other computing device.
[0074] Referring to FIG. 5B, a flowchart illustrating steps of a method of
exchanging an encryption key between the mobile device and the keyboard of
the system shown in FIG. 5A is shown generally as 330a. Steps 332a to 346a
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generally correspond to steps 332 to 346 as described with reference to FIG.
4B,
except that the peripheral device is more specifically a wireless keyboard
310a.
Accordingly, the reader is directed to the description provided herein with
reference to FIGS. 4A and 4B for details in respect of method 330a.
[0075] In one example embodiment as shown in FIG. 5B, the encryption
key is generated at mobile device 100 (step 336a), which is converted to a
string
(step 338a). Conversion of the key into a string format may be considered
particularly appropriate for this specific peripheral device, since a keyboard
is
naturally designed to accept alphanumeric input. The string is then output to
a
user of mobile device 100 (step 340a) through a display (e.g. 110 of FIG. 1)
of
mobile device 100.
[0076] In operation, the user types the string that is output at the mobile
device 100 into wireless keyboard 310a.
[0077] Once the keys are pressed on wireless keyboard 310a, the
characters received from the user through the keyboard are converted into a
string (step 342a), which is then used to recover the encryption key (step
344a).
The encryption key can then be used to encrypt and decrypt data transmitted
between mobile device 100 and wireless keyboard 310a, in accordance with a
data encryption algorithm.
[0078] Accordingly, security can be added to data transmitted over an
existing wireless connection 320 (e.g. Bluetooth) between mobile device 100
and
wireless keyboard 310a, and alteration of the hardware of wireless keyboard
310a is unnecessary.
[0079] Referring to FIG. 6B, a flowchart illustrating steps of a method of
exchanging an encryption key between the mobile device and the printer of the
system shown in FIG. 6A is shown generally as 330b. Steps 332b to 346b
generally correspond to steps 332 to 346 as described with reference to FIG.
4B,
except that the peripheral device is more specifically a peripheral output
device
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such as wireless printer 310b. Accordingly, the reader is directed to the
description provided herein with reference to FIGS. 4A and 4B for details in
respect of method 330b.
[0080] In one embodiment, the encryption key is generated at wireless
printer 310b (step 336b), which is converted to a string (step 338b). The
string is
then output to a user (step 340b) at wireless printer 310b. For example, the
printer could simply print out the string for the user on paper or on another
medium.
[0081] In operation, the user enters the string output at the printer 310b
into mobile device 100. This may be done by entering the string through, for
example, a keyboard (e.g. 116) integrated with mobile device 100, or through
some other input device (e.g. touch screen) or user interface.
[0082] The string received at the mobile device (step 342b) is then used to
recover the encryption key (step 344b). The encryption key can then be used to
encrypt and decrypt data transmitted between mobile device 100 and wireless
printer 310b, in accordance with a data encryption algorithm.
[0083] Accordingly, security can be added to data transmitted over an
existing wireless connection 320 (e.g. Bluetooth) between mobile device 100
and
wireless printer 310b, and alteration of the hardware of wireless printer 310b
is
unnecessary.
[0084] For example, Bluetooth-enabled printers usually have a fixed PIN
associated with them. In atypical cases where it is possible to change a fixed
PIN, desktop software or some other mechanism may be required to change the
PIN. In contrast, in accordance with at least one embodiment, an encryption
key
can be generated every time a mobile device is paired with a wireless
peripheral
device. This provides for greater security, as the encryption key is not hard-
coded in or otherwise fixedly associated with the peripheral device (or the
mobile
device), for example.
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[0085] It will be understood by persons skilled in the art that although
method 330b has been described herein with reference to a wireless printer
310b, in variant embodiments, the peripheral output device may be a device
other than a wireless printer. The manner in which output is provided to the
user
at step 340b may be modified depending on the output capabilities of the
particular peripheral output device.
[0086] It will be understood by persons skilled in the art that the term
"keyboard" is not to be limited to devices that solely provide keyboard or
keypad
input capabilities. Similarly, the term "printer" is not to be limited to
devices that
solely provide printing capabilities. Some peripheral devices may provide
multiple input and/or output capabilities. By way of example, a given device
may
be considered to be a "keyboard" in respect of embodiments described with
reference to FIGS. 5A and 5B, while the same device may also be considered to
be a "printer" in respect of embodiments described with reference to FIGS. 6A
and 6B.
[0087] More generally, a peripheral output device is not restricted to
peripheral output devices that solely provide output to a user. A peripheral
device may be equipped with use input capabilities, but still considered to be
an
output device if it is capable of providing output to a user.
[0088] In embodiments of the invention where a string is to be output at
one of the mobile device and the wireless peripheral device, and is
subsequently
input by the user at the other of the two devices, one of a number of
algorithms
may be employed to convert keys into a string format or to recover keys from a
string.
[0089] Some examples of algorithms that may be employed include, for
example, Public-Key Cryptography Standard #5 (PKCS5) using password-based
key derivation function 2 (PBKDF2), and Simple Password-authenticated
Exponential Key Exchange (SPEKE), or variants thereof. Some of these
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algorithms may not generate a string from an encryption key, but may instead
be
used to generate encryption keys from a string that is shared. The string to
be
shared may be derived from other data (e.g. a password, random data).
[0090] Accordingly, in a variant embodiment, this string rather than an
actual encryption key may instead be first generated at one of the two
devices.
In that case, the encryption key generated at the one device (e.g. at step
336/336a/336b) is generated based on the string (which may have been derived
from other data), using the appropriate string-to-key generation algorithm. In
this
manner, both devices will be able to generate the encryption key.
[0091] To illustrate this variant embodiment by way of example, reference
is made to FIG. 7. Method 330c is similar to method 330 of FIG. 4B, except
that
the above-mentioned string is generated at step 335c (possibly derived from
other data) and output at step 340c at the one device, to be received by the
other
device at step 342c. In another variant embodiment, the string generated at
step
335c may be generated at a third device and provided to the one device.
[0092] The string generated at step 335c would also be used to generate
the encryption key at the one device using the string-to-key generation
algorithm
at step 336c. Step 336c may be performed any time after step 335c, but before
data is to be transmitted over the wireless connection at step 346c. Steps
332c,
334c, 344c, and 346c have been described with reference to steps 332, 334,
344, and 346 of method 330 of FIG. 4B respectively.
[0093] In view of the foregoing, it will be understood that the term "recover"
and its derivations used herein in the specification and in the claims with
reference to recovery of the encryption key (e.g. steps 344/344a/344b) is to
be
interpreted broadly, and may be, for example, interchangeable with the more
general term "generate" and its respective derivations. In particular, the act
of
recovering an encryption key does not presuppose that the actual encryption
key
must first be generated at one device before it is recovered at the other
device.
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For example, as noted above in respect of certain embodiments, an encryption
key may be generated at each of two devices from the same, shared string.
Accordingly, it is not necessary that an encryption key be first "generated"
at one
device in order that the encryption key may be "recovered" at the other
device.
5[0094] It will also be understood by persons skilled in the art that the
order
of the steps of the above methods may be modified in variant embodiments. For
example, encryption keys may be exchanged between two devices in
accordance with an embodiment of a method described herein before the pairing
of two devices is initiated or before a wireless connection between the two
devices is otherwise established. In the case where an encryption key is "pre-
exchanged" in this manner and stored, the encryption key may be subsequently
retrieved and automatically used to encrypt and decrypt data transmitted over
a
wireless connection once the wireless connection is established.
[0095] In variant embodiments of the invention, multiple keys may be
generated and exchanged between two devices. For example, public and/or
private keys may be exchanged between the two devices, and the data
encryption algorithm to be employed in encrypting and decrypting data
transmitted over the wireless connection may be based on public key
cryptography.
[0096] Although the embodiments described herein make reference to a
mobile device and a peripheral device, in variant embodiments, encryption keys
may be exchanged between other computing devices and a peripheral device in
the manner described herein.
[0097] The steps of a method of exchanging an encryption key between a
computing device and a wireless peripheral device in embodiments described
herein may be provided as executable software instructions stored on computer-
readable media, which may include transmission-type media.
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[0098] 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.
