Apparatus for authenticating memory space of an authorized accessory

• US 20040187000A1
• Filed: 02/19/2004
• Published: 09/23/2004
• Est. Priority Date: 07/15/1997
• Status: Active Grant

• Current Assignee: Memjet Technology Ltd. (Memjet Limited)
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Silverbrook, Kia
• Granted Patent: US 7,194,629 B2
• Time in Patent Office: Days
• US Class Current: 713/171
• CPC Class Codes: G06F 21/31 User authentication
• CPC Class Codes: G06F 21/77 in smart cards
• CPC Class Codes: G06F 2221/2103 Challenge-response
• CPC Class Codes: G06F 2221/2129 Authenticate client device independently of the user
• CPC Class Codes: G06F 2221/2143 Clearing memory, e.g. to prevent the data from being stolen
• CPC Class Codes: H04L 2209/043 of tables, e.g. lookup, substitution or mapping
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 9/002 Countermeasures against attacks on cryptographic mechanisms network architectures or network communication protocols for protection against malicious traffic H04L63/1441
• CPC Class Codes: H04L 9/3218 using proof of knowledge, e.g. Fiat-Shamir, GQ, Schnorr, ornon-interactive zero-knowledge proofs
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC
• CPC Class Codes: H04L 9/3271 using challenge-response

Abstract

An apparatus for authenticating memory space of an authorized accessory of a device includes an integrated circuit. The integrated circuit is configured to define two secret keys K₁ and K₂, a random function which returns a random number R and a first parameter being a function of the random number R using the secret key K₁ of the integrated circuit and to define a test function operable on data using the secret key K₂ of the integrated circuit to return a one or a zero. A control system is configured to call the random function of the integrated circuit, to call a read function defined by the accessory using a function of R with the secret key K₁ stored by the accessory as a second parameter, such that the accessory returns a third parameter from the memory space which is a function of R using the secret key K₂ stored by the accessory if the first and second parameters are equivalent, to call the test function using a function of R with the secret key K2 of the integrated circuit as a fourth parameter. The integrated circuit is configured so that the test function returns a one if the third and fourth parameters are equivalent.

Claims

1. An apparatus for authenticating memory space of an authorized accessory of a device, the apparatus comprising

an integrated circuit which is configured to define two secret keys K₁ and K₂, a random function which returns a random number R and a first parameter being a function of the random number R using the secret key K₁ of the integrated circuit and to define a test function operable on data using the secret key K₂ of the integrated circuit to return a one or a zero;

and

a control system which is configured to call the random function of the integrated circuit, to call a read function defined by the accessory using a function of R with the secret key K₁ stored by the accessory as a second parameter, such that the accessory returns a third parameter from the memory space which is a function of R using the secret key K₂ stored by the accessory if the first and second parameters are equivalent, to call the test function using a function of R with the secret key K2 of the integrated circuit as a fourth parameter, the integrated circuit being configured so that the test function returns a one if the third and fourth parameters are equivalent.

2. An apparatus as claimed in claim 1, in which the random, test and read functions are one-way functions.

3. An apparatus as claimed in claim 1, in which the integrated circuit is configured to advance R to next in sequence with each invocation of the random number generator.

4. An apparatus as claimed in claim 3, in which the integrated circuit includes a linear feedback shift register which defines the random number generator.

5. A method of authenticating memory space of an authorized accessory of a device, the method comprising the steps of:

storing secret keys, K1 and K2, in an integrated circuit of the device and in the memory space of the accessory;

generating a random number R and a first parameter being a function of R using the key K₁ of the integrated circuit of the device;

calling a read function defined by the accessory using a second parameter being a function of R using the key K₁ of the accessory;

returning a third parameter, being a function of R using the key K₂ of the accessory if the first and second parameters are equivalent;

calling a test function of the integrated circuit using a fourth parameter being a function of R using the key K₂ of the integrated circuit device; and

returning a one if the third and fourth parameters are equivalent.