GB2407938A

GB2407938A - Set-up of wireless network using mains electrical circuit

Info

Publication number: GB2407938A
Application number: GB0326091A
Authority: GB
Inventors: Russell John Haines
Original assignee: Toshiba Research Europe Ltd
Current assignee: Toshiba Europe Ltd
Priority date: 2003-11-07
Filing date: 2003-11-07
Publication date: 2005-05-11
Also published as: GB0326091D0

Abstract

A wireless network (22) is disclosed that comprises a first device (24) and a second device (34) each connected to a common mains electrical supply circuit (36). The first and second devices (24 and 34) are operable to establish wireless communication between them independence upon setup information (K, CP) communicated from the first device (24) to the second device (34) over the mains electrical supply circuit (36). The setup information (K, CP) may include a private encryption key used to encrypt subsequent wireless communications between the two devices (24 and 34).

Description

The present invention relates to a wireless network, a device for use in a

wireless network and a method of establishing wireless communication between devices in a Figure 1 of the accompanying drawings is a block diagram illustrating the basic setup of a typical wireless network, such as a wireless local area network. The illustrated wireless network 2 comprises a primary device 4 in communication with a first secondary device 6 over a first wireless communications path 8 and also in communication with a second secondary device 10 over a second wireless communications path 12.

Communications between the primary device 4 and the secondary devices 6 and 10 are typically encrypted using a secret encryption key K before transmission to protect against eavesdropping by intruders and also to prevent unauthorised access to the primary device 4. One such security protocol is the wired equivalent privacy (WEP) protocol in which communications are encrypted with a secret key prior to transmission.

The IEEE 802.11 standard specifies a 64-bit WEP key, which comprises a 40bit shared secret, the remaining 24 bits being a non-secret initialization vector. Several proprietary extensions of the IEEE 802.11 standard have emerged, the most common being a 128- bit solution (104-bit shared secret, 24-bit initialization vector), although there are also some 152-bit solutions (128-bit shared secret, 24- bit initialization vector).

With a security protocol such as the WEP protocol, it is of course necessary for each of the devices 4, 6 and 12 in the wireless network 2 to have knowledge of the secret key, and the distribution of the secret key raises both practical and security issues. The distribution of the encryption information must be performed in a manner that is both secure, so that only those devices that are authorised gain knowledge of the secret key, and also user-friendly, to ease the installation process and to prevent installation errors.

This is especially so when the wireless network is being set up in a home environment without skilled IT support or advice.

To explain the process of installing a new device into a wireless network, Figure 1 also illustrates a third secondary device 14 that is to be installed into the existing wireless network 2 such that wireless communication can be established between the primary device 4 and the third secondary device 14. As part of this procedure, the third secondary device 14 must be supplied with the secret key K that is being used by the primary device 4 for wireless communications, as well as other configuration parameters that are required for establishing wireless communication with the primary device 4, such as for example the transmission frequency to be used.

Some current technologies targeted at the home, such as the Digital Enhanced Cordless Telecommunications (DECT) technology and Bluetooth, adopt a "press the button now" approach, where the user is required to set manually both the primary device 4 and the third secondary device 14 into a registration mode as a primitive form of authentication, and then, for a limited period, the two devices 4 and 14 transfer encryption keys K and the like in unencrypted form. This presents a significant risk of eavesdropping, even during that constrained and unpredictable window.

In the commercial wireless local area network environment, the third secondary device 14 would typically be installed into the wireless network 4 by entering the encryption key K manually into the third secondary device 14, for example via a keypad. This overcomes the problem of the eavesdropping of the encryption key K, but in the home entertainment environment the devices envisaged (for example, hi-fi equipment such as speakers, amplifiers and tuners) are likely to have no user interface at all, and highly unlikely to have a full keyboard, and therefore the entry of the required encryption key K into the third secondary device 14 is likely to be difficult. In addition, user- friendliness and the ease of installing a new device are extremely important in the domestic market, and requiring the user to enter encryption keys and other configuration parameters into a new device is likely to be both unpopular and unreliable.

Accordingly it is desirable to provide a wireless network that allows the installation of a new device into the network in a straightforward, reliable and secure manner.

According to a first aspect of the present invention there is provided a method of establishing wireless communication between first and second devices in a wireless network, the first and second devices being connected to a common mains electrical supply circuit, comprising communicating setup information from the first device to the second device over the mains electrical supply circuit and establishing wireless communication in dependence upon the setup information.

The wireless network may be a local area wireless network.

The setup information may comprise a cryptographic key associated with the first device, allowing subsequent wireless communication from the second device to the first device to be encrypted using the cryptographic key. The cryptographic key may be a private encryption key.

The setup information may comprise authentication information, allowing the first device to be authenticated during the establishment of wireless communication. The authentication information may also allow the first device to be authenticated during subsequent wireless communication between the first and second devices. The setup information may comprise information relating to one or more configuration parameters required for establishing wireless communication with the first device. The setup information may comprise the physical address of the first device.

Corresponding such setup information may also be communicated from the second device to the first device over the mains electrical supply circuit following receipt of setup information from the first device. The setup information sent in this reverse direction from the second to the first device may be of the same type as described above but in certain cases would comprise information specific to the second device.

One or both of the first and second devices may receive power from the mains electrical supply circuit.

The method of the first aspect may used to install the second device into an existing wireless network including the first device. This allows for a convenient and reliable method of installation with minimal or no user intervention during installation.

The first device may be a primary device of the wireless network.

The method of the first aspect may be used to replace or alter an existing wireless communications path between the first and second devices. For example, if the private encryption key used to encrypt communications is to be changed, this could be sent over the mains electrical supply circuit such that a new wireless communications path replaces the existing one. Or if the frequency of transmission is to change, this too could be communicated over the mains electrical supply circuit.

According to a second aspect of the present invention there is provided a wireless network comprising first and second devices connected to a common mains electrical supply circuit, wherein the first and second devices are operable to establish wireless communication between them in dependence upon setup information communicated from the first device to the second device over the mains electrical supply circuit.

According to a third aspect of the present invention there is provided a device for use in a wireless network comprising means for communicating setup information to another device of the network over a mains electrical supply circuit and means for establishing wireless communication with the other device in dependence upon the setup information.

According to a fourth aspect of the present invention there is provided a device for use in a wireless network comprising means for receiving setup information from another device of the network over a mains electrical supply circuit and means for establishing wireless communication with the other device in dependence upon the setup information.

According to a fifth aspect of the present invention there is provided a use of a mains electrical supply circuit connected in common to first and second devices of a wireless network as a secondary communications path between the devices, the primary communications path between the devices being a wireless communications path.

According to a sixth aspect of the present invention there is provided a device for use in a wireless network comprising primary communications means for performing wireless communication with another device of the network and secondary communication means for performing communication with the other device over a mains electrical supply circuit connected in common to the first and second devices.

Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a block diagram illustrating a typical wireless network; Figure 2 is a block diagram illustrating a wireless network according to an embodiment of the present invention; Figure 3 is a block diagram illustrating parts of the primary and secondary devices in more detail; and Figure 4 is a flow diagram illustrating a method of establishing wireless communication in a wireless network embodying the present invention.

Figure 2 is a block diagram illustrating a local area wireless network according to an embodiment of the present invention. The illustrated wireless network 22 comprises a primary device 24 in wireless communication with a first secondary device 26 over a first wireless communications path 8 and also with a second secondary device 30 over a second wireless communications path 12. The primary device 24, the first secondary device 26 and the second secondary device 30 are each connected to a common mains electrical supply circuit 36 for receiving power therefrom.

A third secondary device 34 is to be installed into the wireless network 22 such that wireless communication is established between the primary device 24 and the third secondary device 34. To enable wireless communication to be established between the primary device 24 and the secondary device 34, setup information must first be communicated from the primary device 24 to the secondary device 34 so that wireless communication can be established in dependence upon the setup information. In this embodiment, the setup information comprises a private encryption key K which is to be used to encrypt wireless communications between the primary device 24 and the third secondary device 34, as well as various other configuration parameters CP that define the physical setup of the wireless communications path between the primary device 24 and the third secondary device 34.

As mentioned above, a common method to achieve the distribution of the private encryption key K is simply to transmit the key K wirelessly for receipt by the secondary device that is being installed. However, in an embodiment of the present invention, use is made for this purpose of the mains electrical supply circuit 36 which is connected in common to the primary device 24 and to the secondary device 34 being installed. The mains electrical supply circuit 36 is used as a secondary communications path between the two devices, where the primary communications path between the devices is a wireless communications path used to carry normal communications between the two devices.

In this regard, it is generally known that the mains electrical supply circuit can be used as a means for transferring data between devices connected to the supply circuit but it has not previously been proposed to use the mains electrical supply circuit as a secondary communications path where a primary wireless communications path already exists, and in particular not for the specific purpose presented in an embodiment of the present invention. For references to the use of the mains electrical supply circuit for data communication, see: (a) EP 1241800; (b) NZ 329783; (c) "Characterising the Low Voltage Mains as a Communications Medium", Cooper and Jeans, gth International Conference on Metering and Tariffs for Energy Supply, 1999; and (d) "Communication Requirements and Standards for Low Voltage Mains Signalling", Newbury, IEEE Transactions on Power Delivery, vol. 13, issue 1. These references provide technical details concerning the achievement of communication over the mains electrical supply circuit required to implement an embodiment of the present invention.

A more detailed description of the present embodiment will now be made with reference to Figures 3 and 4.

Figure 3 is a block diagram showing parts of the primary device 24 and the secondary device 34 in more detail, while Figure 4 is a flow diagram for use in explaining a method of establishing wireless communication between the primary and secondary devices 24 and 34 in a wireless network embodying the present invention.

As shown in Figure 3, the primary device 24 comprises a control unit 39, a primary communications unit 40 and a secondary communications unit 42. The secondary device 34 comprises a control unit 44, a primary communications unit 46 and a secondary communications unit 48. The primary communications units 40 and 46 are for performing wireless communication between the devices 24 and 34 over a primary communications path 38, being a wireless communications path. The secondary communications units 42 and 48 are for performing communication between the devices 24 and 34 over a secondary communications path 36', being the mains electrical supply circuit 36 connected in common to the primary and secondary devices 24 and 34.

As is illustrated in Figure 4, to establish wireless communication between the primary device 24 and the secondary device 34, the primary device is first connected to the mains electrical supply circuit 36 (S1). Similarly, the secondary device 34 is connected to the mains electrical supply circuit 36 (S2) so as to establish the secondary communications path 36' between the primary device 24 and the secondary device 34.

The control unit 39 of the primary device 24 detects that the secondary device 34 is awaiting installation into the wireless network 24, this detection being achieved for example by receipt at the primary device 24 of signals sent from the secondary device 34 over the electrical supply circuit 36. The control unit 39 then arranges for setup information required for the establishment of the wireless communications path 38 in a secure manner to be communicated to the secondary device 34. The setup information is transmitted from the secondary communications unit 42 of the primary device 24 over the mains electrical supply circuit 36 and is received by the secondary communications unit 48 of the secondary device 34 (S3).

The control unit 44 of the secondary device 34 interprets the received setup information and uses the information to establish the wireless communications path 38. In this embodiment, the setup information comprises one or more configuration parameters required to initialise the primary communications unit 46. The parameters are used to configure the primary communications unit 46 such that wireless communications transmitted by the secondary device 34 over the wireless communications path 38 are properly received and understood by the primary communications unit 40 of the primary device 24. The setup information also comprises the private encryption key K that is to be used to encrypt subsequent wireless communications from the secondary device 34. This private encryption key K is used by the control unit 44 to encrypt subsequent wireless communications before transmission by the primary communications unit 46 over the wireless communications path 38. In this way, wireless communication is established based upon the setup information received (S4).

A major advantage with using the mains electrical supply circuit 36 in this manner to transmit sensitive information such as the private encryption key K is that the sensitive information is never transmitted in unencrypted form over the air waves and is therefore more secure and less prone to eavesdropping by third parties. As described above, the mains electrical supply circuit 36 can also be used to transmit other information such as configuration parameters. A further advantage is that there is no requirement for the user manually to enter in the private encryption key or other configuration information into the secondary device being installed into the wireless network and this allows the setup procedure to be automated with less susceptibility to installation errors and problems caused by an inexperienced user.

A further advantage is that the reliable wired path gives a bidirectional communications capability. Not only can the new device 34 obtain key parameters about the existing system, but it can also transmit key data about itself, such as its unique physical address, which can be used for authentication when the device communicates via the primary (wireless) communications path 38. If the secondary device 34 is to use a different private encryption key for wireless communications in the reverse direction from the secondary device 34 to the primary device 24, the mains electrical supply circuit 36 can also be used for this purpose.

One of the weaknesses of previously-considered wireless local area networks is that there is usually an implicit assumption that the primary device (or access point) is authentic, and therefore that only the secondary devices need to be authenticated. This can lead to a so-called "man in the middle" type of attack, where a rogue device can masquerade as a primary device, and so trick the secondary device into revealing to it secret information held within the secondary device. The rogue primary device can then use the secret information to gain access to the real primary device. It is therefore useful to have the ability to authenticate bi-directionally and to establish the credentials of the primary device. The primary device and the secondary device can mutually authenticate via the mains electrical supply circuit 36, or one can authenticate itself via the mains electrical supply circuit 36 with the other authenticating itself over the wireless communications path.

The use of the mains electrical supply circuit 36 as a secondary communications path 36' is not limited only to the initial setup period but may also be used periodically during the operation of the system, for example as a secure means of exchanging sensitive information where it is suspected that eavesdropping is occurring on the communications over the primary (wireless) communications path 38. The secondary communications path 36' can be used at any time and for any purpose.

The mains electrical supply circuit is implicitly trustworthy, provided that communications are prevented from passing beyond the domestic fuse box, since the user is required physically to plug the devices into the mains outlet which are securely located within the home. It would be extremely difficult for a potential eavesdropper to gain access to the mains electrical supply circuit contained within the users home. This acts as an authentication of the secondary devices connected to the mains electrical supply circuit so that the private key can safely be distributed to any such device.

Although it is usually the case that the devices in the wireless network having access to the mains electrical supply circuit for use as a secondary communications paw would also be receiving power from that mains electrical supply circuit, this is not essential.

For example, a device may be powered by battery and connected to the mains electrical supply circuit solely for the secure and user-friendly installation of the device into the wireless network. Such a batterypowered device may remain connected to the mains electrical supply circuit so that it has access to the mains electrical supply circuit as a secondary communications path throughout.

Although the above wireless network is described as having a primary device and several secondary devices each in communication with the primary device, with the primary device being the device in overall control of me network, it is also possible to use an embodiment of the present invention in an ad hoc wireless network where each device can establish communication directly with any other device of the network.

A wireless network embodying the present invention need not be a local area wireless network, but may in fact allow wireless communication over relatively large distances.

It would of course be required that any devices using a secondary communications path between them as described above are actually connected to a common mains electrical supply circuit for that purpose.

Claims

CLAIMS: 1. A method of establishing wireless communication between first

and second devices in a wireless network, the first and second devices being connected to a common mains electrical supply circuit, comprising communicating setup information from the first device to the second device over the mains electrical supply circuit and establishing wireless communication in dependence upon the setup information.
2. A method as claimed in claim 1, wherein the wireless network is a local area
3. A method as claimed in claim 1 or 2, wherein the setup information comprises a cryptographic key associated with the first device, allowing subsequent wireless communication from the second device to the first device to be encrypted using the cryptographic key.
4. A method as claimed in claim 3, wherein the cryptographic key is a private encryption key.
5. A method as claimed in any preceding claim, wherein the setup information comprises authentication information, allowing the first device to be authenticated during the establishment of wireless communication.
6. A method as claimed in any preceding claim, wherein the setup information comprises authentication information, allowing the first device to be authenticated during subsequent wireless communication between the first and second devices.
7. A method as claimed in any preceding claim, wherein the setup information comprises information relating to one or more configuration parameters required for establishing wireless communication with the first device.
8. A method as claimed in any preceding claim, wherein the setup information comprises the physical address of the first device.
9. A method as claimed in any preceding claim, wherein corresponding such setup information is communicated from the second device to the first device over the mains electrical supply circuit following receipt of setup information from the first device.
10. A method as claimed in any preceding claim, wherein one or both of the first and second devices receive power from the mains electrical supply circuit.
11. A method as claimed in any preceding claim, being a method of installing the second device into an existing wireless network including the first device.
12. A method as claimed in claim 11, wherein the first device is the primary device of the wireless network.
13. A method as claimed in any preceding claim, being a method of replacing or altering an existing wireless communications path between the first and second devices.
14. A wireless network comprising first and second devices connected to a common mains electrical supply circuit, wherein the first and second devices are operable to establish wireless communication between them in dependence upon setup information communicated from the first device to the second device over the mains electrical supply circuit.
15. A device for use in a wireless network comprising means for communicating setup information to another device of the network over a mains electrical supply circuit and means for establishing wireless communication with the other device in dependence upon the setup information.
16. A device for use in a wireless network comprising means for receiving setup information from another device of the network over a mains electrical supply circuit and means for establishing wireless communication with the other device in dependence upon the setup information.
17. Use of a mains electrical supply circuit connected in common to first and second devices of a wireless network as a secondary communications path between the devices, the primary communications path between the devices being a wireless communications path.
18. A device for use in a wireless network comprising primary communications means for performing wireless communication with another device of the network and secondary communication means for performing communication with the other device over a mains electrical supply circuit connected in common to the first and second devices.
19. A method of establishing wireless communication between first and second devices in a wireless network substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.
20. A wireless network substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.
21. A device for use in a wireless network substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.
22. Use of a mains electrical supply circuit substantially as hereinbefore described with reference to Figures 2 to 4 of the accompanying drawings.