GB2381700A

GB2381700A - Verifying the authenticity and integrity of information transmitted over the air to a receiving station at the receiver using hash functions

Info

Publication number: GB2381700A
Application number: GB0126299A
Authority: GB
Inventors: Timothy James Wright
Original assignee: Vodafone Group PLC
Current assignee: Vodafone Group PLC
Priority date: 2001-11-01
Filing date: 2001-11-01
Publication date: 2003-05-07
Anticipated expiration: 2021-11-01
Also published as: GB0126299D0; GB2381700B

Abstract

An arrangement and method are disclosed for authenticating and establishing the integrity of information to be transmitted wirelessly between two units A,B particularly useful where one of the units eg. B is of simple type with small data processing capabilities (e.g. an earpiece for receiving transmissions from a mobile telephone). One unit A transmits its public key wirelessly where it is received TV by the other unit B. In addition and according to a known predetermined algorithm, the first unit A subjects the public key to a hash function II to produce a hash III which is then presented to a user in any suitable form IV, such as on a visual screen. The other unit B subjects the received public key VI to the same hash function VIII to produce an output hash IX which is then displayed non-visually to the user X. Preferably, the non-visual presentation X is an audible presentation. The user can then compare the visual presentation TV by the first unit A with the audible presentation X by the second unit B and thereby check the authenticity and integrity of the received public key. The need for a visual display screen on the other unit B is therefore avoided.

Description

TELECOMMUNICATION SECURITY ARRANGEMENTS AND METHODS The invention relates to telecommunication security arrangements and methods. In embodiments of the invention to be described in more detail below, by way of example only, the authenticity and integrity of information transmitted over the air to a receiving station from a transmitting station can be verified at the receiving station.

It is known to use a public/private key system for authenticating information transmitted by a transmitting station. Thus, for example, the transmitting station may encrypt information using its private key (part of a public/private key pair) and then transmit the encrypted information. If (but only if) the receiving station knows the transmitting station's public key, it can decrypt the message. This will serve to show that the message can only have been encrypted by that transmitting station, and thus serve to authenticate the message. In order for such a system to be satisfactory, though, it is of course necessary for the receiving station to be sure that the public key which it has is indeed the public key of the particular transmitting station. It is known in such an arrangement for the public key to be transmitted in association with a certificate from a trusted Certification Authority. In such a case, the receiving station must have relatively complex certificate verification software and a root certificate corresponding to the private key which has been used to issue the transmitting station's certificate. Circumstances may arise where this is impractical. Increasingly, electronic units which need to be interconnected to produce a functioning system are being interconnected wirelessly. For

example, units may be interconnected wirelessly using the BLUETOOTH (TM) protocol.

In a case where one or both of two units to be wirelessly interconnected is a relatively simple device, it may be impractical to be able to contain and/or use the complex certificate verification software mentioned above; to do so may require a relatively large amount of memory space. Furthermore, transmission of the certificate, which will be longer than the public key itself, uses up substantial bandwidth.

According to the invention, there is provided an arrangement for enabling a user-check of the authenticity and integrity of data transmitted wirelessly from a transmitting station to a receiving station, comprising means in the transmitting station for transmitting the data to the receiving station, means in the transmitting station for producing a hash ("originating hash") of the data according to a predetermined algorithm, presentation means in the transmitting station for presenting that hash to the user, means in the receiving station for receiving the transmitted data, means in the receiving station for producing a hash ("secondary hash") of the received data according to the predetermined algorithm, and presentation means in the receiving station for presenting the secondary hash to the user whereby to enable the user to compare the hashes respectively presented by the presentation means and thereby to check the authenticity and integrity of the received data, at least one of the presentation means presenting the respective hash nonvisually.

According to the invention, there is further provided a method for enabling a user-check

of the authenticity and integrity of data transmitted wirelessly from a transmitting station to a receiving station, comprising the steps of transmitting the data from the transmitting station to the receiving station, producing a hash ("originating hash") of the transmitted data according to a predetermined algorithm, presenting that hash to the user, receiving the transmitted data at the receiving station, producing a hash ("secondary hash") of the received data according to the predetermined algorithm, and presenting the secondary hash to the user whereby to enable the user to compare the hashes respectively presented by the presentation means and thereby to check the authenticity and integrity of the received data at least one of the hashes being presented non-visually.

Telecommunications security arrangements and methods according to the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a block diagram of two units between which a secure wireless interconnection is to be set up; and Figure 2 is a block diagram for explaining the operation of the arrangements and methods.

Figure 1 shows two units A and B between which a secure wireless interconnection is to be set up. In a particular example, units A and B are to communicate with each other wirelessly using a BLUETOOTH (TM) protocol. Units A and B can be of any particular

type. The arrangements and methods to be described in more detail are particularly suitable, though, where one of the units (unit B for example) is relatively simple compared with the other unit (unit A).

It is envisaged that the security of transmission between unit A and unit B will be ensured by authentication using a public/private key arrangement. Thus, unit A will use its own private key (not in principle known outside unit A) to encrypt messages intended for unit B. Unit B will decrypt the received messages using unit's A's public key. If the received message can be decrypted, then this establishes that the message did indeed originate from unit A. Equally, Unit B can encrypt messages using A's public key. As these can only be decrypted using A's private key, messages encrypted using A's public key can only be decrypted by A.

In order for either of these processes to operate, it is clearly necessary that unit B is in possession of unit A's public key and is satisfied as to the authenticity and integrity of that key. As shown in Fig. 1, unit A's public key is transmitted wirelessly to unit B by a transmitter T where it is received by a receiver R and must then be authenticated by an authentication unit AU. Authentication of unit A's public key, when transmitted to unit B, could be achieved by means of a Certificate issued by a trusted Certification Authority and transmitted with the public key to unit B. However, unit A would have to obtain such a certificate from the Certificate Authority which is a relatively complex and expensive process. The certificate is be longer than the public key itself and would use up

substantial memory space in unit A, substantial bandwidth during its transmission to unit B, and substantial memory space in unit B. Unit B would also need complex certificate verification software and also a root certificate corresponding to the private key used to issue the unit A's certificate. In the case where unit B is a relatively simple appliance, the implementation of such complexity may be impossible. For example, unit A could be a mobile terminal in a cellular telecommunication system such as a mobile telephone handset, and unit B could be a simple earpiece to be worn by a user and for receiving voice calls to the handset, in which case it would be impractical for the ear piece to contain all the necessary software and memory for processing a verifying certificate transmitted with unit A's public key. As shown in Figure 1, the public key is received in unit B by a receiver R and then subjected to authentication which will now be described with reference to Figure 2.

Figure 2 shows, diagrammatically, the operations which take place within the units A and B to overcome the problems discussed above. More particularly, Figure 2 shows how unit A transmits its public key to unit B and how unit B can confirm the authenticity and integrity of the public key.

As shown at I in Figure 2, unit A is in possession of its public key. This public key is now subjected to a hash function (II) according to a simple algorithm which is agreed between unit A and unit B, so as to produce a hash of the public key as shown at III. The hash is then presented by unit A, as shown at IV, in a suitable way, as will be described

in more detail below. As an example, though, the hash can be simply displayed on a screen such as in suitable alphanumeric form.

In addition, unit A transmits its public key to unit B as shown at V.

As shown at VI, the unit B receives the transmitted public key which may be passed to memory as shown at VII.

In addition, though, the unit B subjects the received public key to the hash function, as shown at VIII, in accordance with the agreed algorithm, so as to produce a corresponding hash (IX). The resultant hash is then output at X.

It is now necessary for a comparison to be made by the user between the hash which is output by unit A at IV and the hash which is output by unit B at X. If both hash outputs agree, then unit B will accept the public key stored in memory at VII. If the two hash outputs do not agree, the public key will be rejected.

As indicated above, the unit A could output the hash at IV by displaying it on a visual screen. If unit B also has a screen, then it can output the hash at X by displaying it on its screen. The user can then make a simple visual comparison to check agreement between the two displayed hashes, thus confirming the authenticity and integrity of the received public key. However, if unit B is a simple unit, such as the earpiece suggested above, it

will not be possible or practicable for it to incorporate a visual screen. In accordance with a feature of the invention, therefore, the hash output of unit B, at X, is presented in some other suitable way not involving the use of a visual screen. For example, the hash output at X can be an audible output in which the alphanumeric characters of the hash are presented audibly to the user of unit B who can then compare the hash so presented and received by unit B with the visual hash presented by unit A at IV and shown visually on unit A's screen.

In this way, therefore, the problems presented by the simple nature of unit B are overcome.

Various modifications may be made.

For example, unit A may itself present the hash audibly instead of (or in addition to) its visual presentation, the audible presentations of the hashes by the units A and B being presented sequentially, and in association with suitable identification, to enable their comparison by the user.

The audible presentation need not be a direct alphanumeric audible presentation of the actual hash. Instead, for example, the hash audibly presented at IV by unit A could be presented after conversion, by means of an agreed converting algorithm, into an audible pitch (or sequence of pitches). Using the same conversion algorithm, unit B would

convert its received hash into a pitch or sequence of pitches presented audibly. Again, therefore, the user could check the authenticity and integrity of the received public key by comparing the pitches audibly emitted by units A and B.

In a further modification, each unit could convert the respective hash into a word, using the same conversion algorithm. Unit A could then display this word at IV, or present it audibly. Unit B would audibly present the word which it converts from the received hash at VII. The user can then compare the two words to check the authenticity and integrity of the received public key.

Although the foregoing description has concerned the authentication of a public key, the features described could be used to authenticate data in other forms.

Claims

1. An arrangement for enabling a user-check of the authenticity and integrity of data transmitted wirelessly from a transmitting station to a receiving station, comprising means in the transmitting station for transmitting the data to the receiving station, means in the transmitting station for producing a hash ("originating hash") of the data according to a predetermined algorithm, presentation means in the transmitting station for presenting that hash to the user, means in the receiving station for receiving the transmitted data, means in the receiving station for producing a hash ("secondary hash") of the received data according to the predetermined algorithm, and presentation means in the receiving station for presenting the secondary hash to the user whereby to enable the user to compare the hashes respectively presented by the presentation means and thereby to check the authenticity and integrity of the received data, at least one of the presentation means presenting the respective hash non-visually.

2. An arrangement according to claim 1, in which the other presentation means presents the respective hash visually.

3. An arrangement according to claim 1, in which the other presentation means presents the respective hash audibly.

4. An arrangement according to any preceding claim, in which the or each

presentation means which presents the respective hash non-visually presents it audibly in alphanumeric form.

5. An arrangement according to claim 4, in which the or each presentation means which presents the hash audibly in alphanumeric form presents it after conversion into, and as, a pronounceable word.

6. An arrangement according to any one of claims 1 to 3, in which the or each presentation means which presents the hash audibly presents it in the form of an audible pitch or sequence of different audible pitches.

7. An arrangement according to any preceding claim, in which the data is a public key of a private/public key pair.

8. A method for enabling a user-check of the authenticity and integrity of data transmitted wirelessly from a transmitting station to a receiving station, comprising the steps of transmitting the data from the transmitting station to the receiving station, producing a hash ("originating hash") of the transmitted data according to a predetermined algorithm, presenting that hash to the user, receiving the transmitted data at the receiving station, producing a hash ("secondary hash") of the received data according to the predetermined algorithm, and presenting the secondary hash to the user whereby to enable the user to compare the hashes respectively presented by the

presentation means and thereby to check the authenticity and integrity of the received data at least one of the hashes being presented non-visually.

9. A method according to claim 8, in which the other hash is presented visually.

10. A method according to claim 8, in which the other hash is presented audibly.

11. A method according to any one of claims 8 to 10, in which the or each hash which is presented non-visually is presented in alphanumeric form.

12. A method according to claim 11, in which the or each hash which is presented audibly in alphanumeric form is presented after conversion into, and as, a pronounceable word.

13. A method according to any one of claims 8 to 10, in which the or each hash which is presented audibly is presented in the form of an audible pitch or sequence of different audible pitches.

14. A method according to any one of claims 8 to 13, in which the data is a public key of a private/public key pair.

15. An arrangement for checking the authenticity and integrity of data transmitted

- from a transmitting station to a receiving station, substantially as described with reference to the accompanying drawings.

16. A method for checking the authenticity and integrity of data transmitted from a transmitting station to a receiving station, substantially as described with reference to the accompanying drawings.