Apparatus and Method for Producing a Message Authentication Code

• US 20130195266A1
• Filed: 01/21/2013
• Published: 08/01/2013
• Est. Priority Date: 01/26/2012
• Status: Active Application

• Current Assignee: Infineon Technologies AG
• Original Assignee: Infineon Technologies AG
• Inventors: Fischer, Wieland
• Application Number:
  US13/746,046
• Publication Number:
  US 20130195266A1
• Time in Patent Office: Days
• US Class Current: 380/44
• CPC Class Codes: H04L 2209/046 of operations, operands or results of the operations
• CPC Class Codes: H04L 9/003 for power analysis, e.g. differential power analysis [DPA] or simple power analysis [SPA]
• CPC Class Codes: H04L 9/0643 Hash functions, e.g. MD5, SHA, HMAC or f9 MAC
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords

Abstract

An apparatus for producing a message authentication code based on a first message and an original key is provided. The apparatus includes a key generator configured to produce a generated key based on the original key and the first message. Furthermore, the apparatus includes a message authentication code generator configured to produce the message authentication code based on the generated key and the first message.

Claims

1. An apparatus for producing a message authentication code based on a first message and an original key, comprising:

a key generator configured to produce a generated key based on the original key and the first message; and

a message authentication code generator configured to produce the message authentication code based on the generated key and the first message.

2. The apparatus according to claim 1, wherein the key generator is configured to produce the generated key by using a cryptographic encryption algorithm.

3. The apparatus according to claim 1, wherein the key generator is configured to produce the generated key by a hash calculation for the first message.

4. The apparatus according to claim 1, wherein the key generator is configured to produce the generated key by performing a hash calculation for a portion of the first message.

5. The apparatus according to claim 1, wherein the key generator is configured to produce the generated key such that an entropy of the generated key is not lower than the entropy of the original key.

6. The apparatus according to claim 1, wherein the key generator is configured to produce the generated key such that when precisely one bit of the first message or of the original key is changed, between 45% and 55% of the bits of the generated key change on average when the generated key is produced again.

7. The apparatus according to claim 1, wherein the key generator is configured to use AES encryption for producing the generated key.

8. The apparatus according to claim 1, wherein the key generator is configured to apply AES_k(H(M)), where M denotes the first message, H(M) denotes the hash calculation of the first message M, k denotes the original key and AES_k denotes an AES encryption using the original key k.

9. The apparatus according to claim 1, wherein the key generator is configured to protect the production of the generated key against side channel attacks.

10. The apparatus according to claim 9, wherein the key generator is configured to perform a masking operation for the first message in order to obtain a masked message, and produce the generated key based on the original key and the masked message.

11. The apparatus according to claim 10, wherein the masking operation comprises exchange of bits of the first message or XORing, ANDing or ORing of the first message with a bit string.

12. The apparatus according to claim 1, wherein the message authentication code generator is configured to perform a hash calculation for the first message to produce the message authentication code.

13. The apparatus according to claim 12, wherein the message authentication code generator is configured to use a first XOR operation to logically combine the generated key with a first constant, and use a second XOR operation to logically combine the generated key with a second constant.

14. The apparatus according to claim 13, wherein the message authentication code generator is configured to apply HMAC_k′

(M)=H((k′

⊕

opad)∥

H((k′

⊕

ipad)∥

M)) in order to calculate the message authentication code, where M is the first message, k′

is the generated key, ⊕

is an XOR operation, ∥

is a concatenation and H is a hash operation.

15. An apparatus for checking correctness and authenticity of a message, comprising:

a key generator configured to produce a generated key based on the original key and the first message;

a message authentication code generator configured to produce the message authentication code based on the generated key and the first message; and

a comparison unit configured to check the message authentication code and a received message authentication code for a match in order to check correctness and authenticity of the message.

16. A method for producing a message authentication code based on a first message and an original key, the method comprising:

producing a generated key based on the original key and the first message; and

producing the message authentication code based on the generated key and the first message.

17. The method according to claim 16, wherein the generated key is produced by using a cryptographic encryption algorithm.

18. The method according to claim 16, wherein the generated key is produced by a hash calculation for the first message.

19. The method according to claim 16, wherein the message authentication code is calculated by applying HMAC_k′

(M)=H((k′

⊕

opad)∥

H((k′

⊕

ipad)∥

M)), where M is the first message, k′

is the generated key, ⊕

is an XOR operation, ∥

is a concatenation and H is a hash operation.

20. The method according to claim 16, further comprising checking the message authentication code and a received message authentication code for a match in order to check correctness and authenticity of the message.