Method for the generation of pseudo-random permutation of an N-digit word

• US 20040208321A1
• Filed: 02/05/2004
• Published: 10/21/2004
• Est. Priority Date: 02/27/2003
• Status: Abandoned Application

• Current Assignee: Jean-Philippe Wary
• Original Assignee: Jean-Philippe Wary
• Inventors: Wary, Jean-Philippe
• Application Number:
  US10/772,798
• Publication Number:
  US 20040208321A1
• Time in Patent Office: Days
• US Class Current: 380/268
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• 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

Abstract

A method for the generation of small permutations on digits, for example between 7 and 30 digits, uses basic functions that are classic, one-way functions (generally non-bijective) defined on bits, and uses these functions in a generalized Feistel scheme that has at least five rounds.

Claims

1. A method for the generation of a pseudo-random permutation of an n-digit word in which:

a generalized Feistel scheme is implemented, wherein;

the round functions of the generalized Feistel scheme implemented are functions (Fi) such that;

the input words of the round functions are produced by the conversion of digit words into binary words,

then a one-way function is applied to these binary words,

finally, the output in digits is a function of these binary words.

a digit word to be enciphered is read in a memory,

the generalized Feistel scheme used comprises at least T=5 rounds.

2. A method according to claim 1, wherein the one-way function on the binary words uses a standard pseudo-random cryptography function on binary words.

3. A method according to claim 1 wherein the standard pseudo-random function on the binary words uses the SHA-1 function.

4. A method according to claim 1 wherein the number of rounds T of the Feistel heme is smaller than or equal to 30.

5. A method according to one of the claims claim 1, wherein the number of rounds T of the Feistel heme is equal to 6.

6. A method according to claim 1 wherein, during odd-valued rounds of the Feistel scheme, the round function works on a word with a length B, and during even-valued rounds of the Feistel scheme it works on words with a length of A digits, where A+B=N.

7. A method according to claim 6, wherein A is equal to the integer part of N/2 and B is equal to N−

A.

8. A method according to claim 1, wherein N is an integer contained in the interval [7, 30].

9. A method according to claim 1, wherein N is an integer contained in the interval [10, 30].

10. A method according to claim 1, wherein N is an integer contained in the interval [13, 30].