Cipher mixer with random number generator

• US 6,351,539 B1
• Filed: 09/18/1998
• Issued: 02/26/2002
• Est. Priority Date: 09/18/1998
• Status: Expired due to Fees

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Inventors: Djakovic, Vladan
• Primary Examiner(s): Peeso, Thomas R.
• Assistant Examiner(s): JACK, TODD M
• Application Number:
  US09/156,774
• Time in Patent Office: 1,257 Days
• Field of Search: 380/268, 380/44, 380/46
• US Class Current: 380/268
• CPC Class Codes: H04L 9/0625 with splitting of the data block into left and right halves, e.g. Feistel based algorithms, DES, FEAL, IDEA or KASUMI
• CPC Class Codes: H04L 9/0662 with particular pseudorandom sequence generator

Abstract

An encryption device has a random number generator whose output is combined by exclusive-or with plaintext input which has been encrypted by a first block cipher. The combined exclusive-or output is encrypted with a second block cipher mechanism which produces a second enciphered output. The output of the random number generator is also encrypted by a third block cipher mechanism which produces a third enciphered output. The first and second block cipher mechanisms differ from each other.

Claims

1. An encryption device comprising:

a random number generator;

a first block cipher mechanism which takes a plaintext input and which produces a first enciphered output based on the plaintext and on a first key;

an exclusive-or mechanism which takes as input the first enciphered output from the first block cipher and the output of the random number generator and which produces a combined output being an exclusive-or combination of the two inputs;

a second block cipher mechanism which takes as input the output of the exclusive-or mechanism and which produces a second enciphered output based on the output of the exclusive-or mechanism and on a second key; and

a third block cipher mechanism which takes as input the output of the random number generator and which produces a third enciphered output based on the output of the random number generator and on a third key,

wherein the first and second block cipher mechanisms differ from each other.

2. A device as in claim I wherein the first, second and third block cipher mechanisms are selected from the group comprising:

an IDEA block cipher and a Blowfish block cipher.

3. A device as in claim 2 wherein the first and third block cipher mechanisms are Blowfish block ciphers and the second block cipher is the IDEA block cipher.

4. A device as in claim 3 wherein the plaintext input is a sequence of 64-bit values and wherein the output of the random number generator is a sequence of 64-bit random values.

5. A device as in claim 3 wherein the first and second keys are 128-bit keys and wherein the third key is a 256-bit key.

6. A device as in claim I wherein the random number generator is a true random number generator.

7. An encryption device comprising:

a true random number generator which generates a sequence of 64-bit random values;

a first block cipher mechanism implementing a Blowfish block cipher which takes a 64-bit plaintext input and which produces a first enciphered output based on the plaintext and on a 128-bit first key;

an exclusive-or mechanism which takes as input the first enciphered output from the first block cipher and the output of the true random number generator and which produces a combined output being an exclusive-or combination of the two inputs;

a second block cipher mechanism implementing an IDEA block cipher which takes as input the output of the exclusive-or mechanism and which produces a second enciphered output based on the output of the exclusive-or mechanism and on a second 128-bit key; and

a third block cipher mechanism implementing the Blowfish block cipher which takes as input the output of the random number generator and which produces a third enciphered output based on the output of the random number generator and on a 256-bit key.

8. A device for decrypting an input stream comprising encrypted data, the data including plaintext, the device comprising:

a demultiplexer for splitting the input stream into a first and a second stream;

a first block cipher mechanism for decrypting the first stream based on a first key to produce a third stream;

a second block cipher mechanism for decrypting the second stream based on a second key to produce a fourth stream;

an exclusive-or mechanism to combining the third and fourth streams into a fifth stream; and

a third block cipher mechanism for decrypting the fifth stream based on a third key to produce the plaintext,

wherein the first and third block cipher mechanisms differ from each other.

9. A device as in claim 8 wherein the first, second and third block cipher mechanisms are selected from the group comprising:

an IDEA block cipher and a Blowfish block cipher.

10. A device as in claim 9 wherein the first block cipher mechanism the IDEA block cipher and the third block cipher is the Blowfish block cipher.

11. A device as in claim 8 wherein the first key is a 128-bit key, the second key is a 256-bit key and the third key is a 128-bit key.

12. A method of encrypting plaintext data comprising:

encrypting the plaintext data with a first block cipher mechanism to produce first encrypted data;

producing a sequence of random values;

combining the first encrypted data with the sequence of random values;

encrypting, with a second block cipher mechanism, the combined first encrypted data and the random values to produce second encrypted data;

encrypting the sequence of random values with a third block cipher mechanism to produce encrypted random values; and

combining the encrypted random values with the second encrypted data to produce the encrypted plaintext data, wherein

the first and second block cipher mechanisms differ from each other.

13. A method as in claim 12 wherein the first, second and third block cipher mechanisms are selected from the group comprising:

an IDEA block cipher and a Blowfish block cipher.

14. A method as in claim 13 wherein the first and third block cipher mechanisms implement Blowfish block ciphers and the second block cipher implements the IDEA block cipher.

15. A method as in claim 14 wherein the plaintext input is a sequence of 64-bit values and wherein the output of the random number generator is a sequence of 64-bit random values.

16. A method as in claim 12 wherein each block cipher mechanism uses a different cryptographic key.

17. A method as in claim 15 wherein the first block cipher mechanism uses a first 128-bit key, the second block cipher mechanism uses a 128-bit key and the third block cipher mechanism uses a second 256-bit key.

18. A method as in claim 12 wherein the sequence of random values is a sequence of true random values.

19. A method for decrypting an input stream comprising encrypted data, the data including plaintext, the method comprising:

splitting the input stream into a first and a second stream;

decrypting, using a first block cipher mechanism, the first stream based on a first key to produce a third stream;

decrypting, using a second block cipher mechanism, the second stream based on a second key to produce a fourth stream;

combining the third and fourth streams into a fifth stream; and

decrypting, using a third block cipher mechanism, the fifth stream based on a third key to produce the plaintext,

wherein the first and third block cipher mechanisms differ from each other.

20. A method as in claim 19 wherein the first, second and third block cipher mechanisms are selected from the group comprising:

an IDEA block cipher and a Blowfish block cipher.

21. A method as in claim 20 wherein the first block cipher mechanism is the IDEA block cipher and the third block cipher is the Blowfish block cipher.

22. A method as in claim 19 wherein each block cipher mechanism uses a different cryptographic key.

23. A method as in claim 22 wherein the first block cipher mechanism uses a first 128-bit key, the second block cipher mechanism uses a 256-bit key and the third block cipher mechanism uses a second 128-bit key.

24. A data processing method for communicating data between a first and a second computers, the method comprising:

(A) on the first computer;

(a) encrypting plaintext data with a first block cipher mechanism to produce first encrypted data;

(b) producing a sequence of random values;

(c) combining the first encrypted data with the sequence of random values;

(d) encrypting, with a second block cipher mechanism, the combined first encrypted data and the random values to produce second encrypted data;

(e) encrypting the sequence of random values with a third block cipher mechanism to produce encrypted random values;

(f) combining the encrypted random values with the second encrypted data to produce the encrypted plaintext data; and

(g) transmitting the combined data to the second computer,

wherein the first and second block cipher mechanisms differ from each other,

(B) on the second computer;

(a) obtaining as an input stream the transmitted combined data from the first computer;

(b) splitting the input stream into a first and a second stream;

(c) decrypting, using a fourth block cipher mechanism, the first stream to produce a third decrypted stream;

(d) decrypting, using a fifth block cipher mechanism, the second stream to produce a fourth decrypted stream;

(e) combining the third a nd fourth decrypted streams into a fifth decrypted stream; and

(f) decrypting, using a sixth block cipher mechanism, the fifth decrypted stream to produce the plaintext.

25. A method as in claim 24 wherein the first, second, third, fourth, fifth and sixth block cipher mechanisms are selected from the group comprising:

an IDEA block cipher and a Blowfish block cipher.

26. A method as in claim 25 wherein the first, third, fifth and sixth block cipher mechanisms implement Blowfish block ciphers and the second and fourth block cipher mechanisms implement the IDEA block cipher.

27. A method as in claim 24 wherein the plaintext input is a sequence of 64-bit values and wherein the output of the random number generator is a sequence of 64-bit random values.

28. A method as in claim 24 wherein the first block cipher mechanism uses a first 128-bit key, the second block cipher mechanism uses a 128-bit key, the third block cipher mechanism uses a second 256-bit key, the fourth block cipher mechanism uses the second 128-bit key, the fifth block cipher mechanism uses the 256-bit key, and the sixth block cipher mechanism uses the first 128-bit key.

29. A method as in claim 24 wherein the sequence of random values is a true sequence of random values.