Encryption apparatus and method, and decryption apparatus and method based on block encryption

• US 20010024502A1
• Filed: 03/06/2001
• Published: 09/27/2001
• Est. Priority Date: 03/06/2000
• Status: Active Grant

• Current Assignee: Kabushiki Kaishi Toshiba
• Original Assignee: Kaubushiki Kaisha Toshiba
• Inventors: Kawamura, Shinichi, Ohkuma, Kenji, Muratani, Hirofumi, Sano, Fumihiko
• Granted Patent: US 7,227,948 B2
• Time in Patent Office: Days
• US Class Current: 380/46
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 2209/12 Details relating to cryptographic hardware or logic circuitry
• CPC Class Codes: H04L 2209/24 Key scheduling, i.e. generating round keys or sub-keys for block encryption
• 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 9/0631 Substitution permutation network [SPN], i.e. cipher composed of a number of stages or rounds each involving linear and nonlinear transformations, e.g. AES algorithms

Abstract

An encryption apparatus for block data, comprises a first processing unit randomizing the block data in units of first portions obtained by dividing the block data, and a second processing unit diffusing the block data output from the first processing unit with respect to a second portion of the block data which is wider than the first portion. The first processing unit comprises first nonlinear processing units nonlinearly transforming the block data in units of the first portions. The second processing unit comprises a first linear diffusion processing unit linearly diffusing the second portion of the block data. At least one of the first nonlinear processing units comprises second nonlinear processing units nonlinearly transforming the block data in units of the first portions, and a second linear diffusion processing unit linearly diffusing the second portion of the block data.

Claims

1. An apparatus for encrypting block data, comprising:

a first processing unit configured to randomize the block data in units of first portions obtained by dividing the block data; and

a second processing unit configured to diffuse the block data output from said first processing unit with respect to a second portion of the block data which is wider than the first portion.

2. The apparatus according to

claim 1

, wherein

said first processing unit comprises first nonlinear processing units configured to respectively nonlinearly transform the block data in units of the first portions;

said second processing unit comprises a first linear diffusion processing unit configured to linearly diffuse the second portion of the block data; and

at least one of said first nonlinear processing units comprises;

second nonlinear processing units configured to nonlinearly transform the block data in units of the first portions; and

a second linear diffusion processing unit configured to linearly diffuse the second portion of the block data.

3. The apparatus according to

claim 2

, wherein said first linear diffusion processing unit performs an arithmetic operation using a Maximum Distance Separable matrix.

4. The apparatus according to

claim 3

, wherein only predetermined lower bits of all elements of said Maximum Distance Separable matrix are nonzero.

5. The apparatus according to

claim 3

, wherein all elements on one row of said Maximum Distance Separable matrix have different values.

6. The apparatus according to

claim 3

, wherein said first linear diffusion processing unit includes a Maximum Distance Separable matrix to which are supplied corresponding bits of the first portions of the block data.

7. The apparatus according to

claim 2

, wherein said second linear diffusion processing unit performs an arithmetic operation using a Maximum Distance Separable matrix.

8. The apparatus according to

claim 1

, further comprising:

a key generation section configured to generate key data depending on the number of stages, said key generation section comprising key generators connected in series, each of said key generators comprising a first circuit configured to nonlinearly transform an output of a preceding generator, a second circuit configured to nonlinearly transform an output of a generator which precedes said preceding generator, and a third circuit configured to EX-OR outputs of said first and second circuits.

9. An apparatus for encrypting block data, comprising:

stage sections connected in series, each of said stage section comprising four first nonlinear processing units and a first linear diffusion processing unit, said four first nonlinear processing units configured to receive input 128-bit plaintext block data at a first stage or 128-bit block data processed by a preceding stage at a second and subsequent stages, and linearly diffuse and nonlinearly transform four sets of 32-bit data obtained by dividing the 128-bit block data, and said first linear diffusion processing unit configured to linearly diffuse 128-bit block data obtained by coupling the four sets of 32-bit data output from said four first nonlinear processing units using a Maximum Distance Separable matrix;

four second nonlinear processing units connected to the last stage of said stage sections and configured to linearly diffuse and nonlinearly transform four sets of 32-bit data obtained by dividing the 128-bit block data; and

a first key addition section connected to said four second nonlinear processing units configured to add 128-bit key data to 128-bit block data obtained by coupling the four sets of 32-bit data output from said four second nonlinear processing units; and

each of said first nonlinear processing units and second nonlinear processing units comprising;

four second key addition sections configured to add 8-bit key data to four sets of 8-bit data obtained by dividing one of the four sets of 32-bit data;

four second nonlinear processing units configured to nonlinearly transform outputs of said four second key addition sections by using an input/output table of 8-bit;

a second diffusion processing unit configured to linearly diffuse 32-bit data obtained by coupling four sets of 8-bit data output from said four second nonlinear processing units using a Maximum Distance Separable matrix; and

four third key addition sections which are the same as said second key addition sections and a third nonlinear processing unit, which are connected to said second diffusion processing unit.

10. An apparatus for encrypting block data, comprising:

stage sections connected in series, each of said stage section comprising two first nonlinear processing units and a first linear diffusion processing unit, said two first nonlinear processing units configured to receive input 64-bit plaintext block data at a first stage or 64-bit block data processed by a preceding stage at a second and subsequent stages, and linearly diffuse and nonlinearly transform two sets of 32-bit data obtained by dividing the 64-bit block data, and said first linear diffusion processing unit configured to linearly diffuse 64-bit block data obtained by coupling the two sets of 32-bit data output from said two first nonlinear processing units using a Maximum Distance Separable matrix;

two second nonlinear processing units connected to the last stage of said stage sections and configured to linearly diffuse and nonlinearly transform two sets of 32-bit data obtained by dividing the 64-bit block data; and

a first key addition section connected to said two second nonlinear processing units configured to add 64-bit key data to 64-bit block data obtained by coupling the two sets of 32-bit data output from said two second nonlinear processing units; and

each of said first nonlinear processing units and second nonlinear processing units comprising;

two second key addition sections configured to add 8-bit key data to two sets of 8-bit data obtained by dividing one of the two sets of 32-bit data;

two second nonlinear processing units configured to nonlinearly transform outputs of said two second key addition sections by using an input/output table of 8-bit;

a second diffusion processing unit configured to linearly diffuse 32-bit data obtained by coupling two sets of 8-bit data output from said two second nonlinear processing units using a Maximum Distance Separable matrix; and

two third key addition sections which are the same as said second key addition sections and a third nonlinear processing unit, which are connected to said second diffusion processing unit.

11. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein, the computer readable program code means comprising:

first computer readable program code means for causing a computer to randomize the block data in units of first portions obtained by dividing the block data; and

second computer readable program code means for causing a computer to diffuse the block data output from said first processing unit with respect to a second portion of the block data which is wider than the first portion.

12. The article of manufacture according to

claim 11

, wherein said first computer readable program code means performs a nonlinear transformation processing with respect to the block data in units of the first portions;

said second computer readable program code means performs a linear diffusion processing with respect to the second portion of the block data; and

said nonlinear transformation processing comprises;

a nonlinear transformation of the block data in units of the first portions; and

a linear diffusion of the second portion of the block data.

13. An method of encrypting block data, comprising:

randomizing the block data in units of first portions obtained by dividing the block data; and

diffusing the randomized block data with respect to a second portion of the block data which is wider than the first portion.

14. The method according to

claim 13

, wherein said randomizing comprises a nonlinear transformation of the block data in units of the first portions;

said diffusing comprises a linear diffusion of the second portion of the block data; and

said nonlinearly transformation comprises;

a nonlinear transformation of the block data in units of the first portions; and

a linear diffusion of the second portion of the block data.

15. An apparatus for decrypting encrypted block data, comprising:

a first processing unit configured to randomize the encrypted block data in units of first portions obtained by dividing the encrypted block data; and

a second processing unit configured to diffuse the encrypted block data output from said first processing unit with respect to a second portion of the encrypted block data which is wider than the first portion.

16. The apparatus according to

claim 15

, wherein

said first processing unit comprises first nonlinear processing units configured to respectively nonlinearly transform the encrypted block data in units of the first portions;

said second processing unit comprises a first linear diffusion processing unit configured to linearly diffuse the second portion of the encrypted block data; and

at least one of said first nonlinear processing units comprises;

second nonlinear processing units configured to nonlinearly transform the encrypted block data in units of the first portions; and

a second linear diffusion processing unit configured to linearly diffuse the second portion of the encrypted block data.

17. An article of manufacture comprising a computer usable medium having computer readable program code means embodied therein, the computer readable program code means comprising:

first computer readable program code means for causing a computer to randomize the encrypted block data in units of first portions obtained by dividing the encrypted block data; and

second computer readable program code means for causing a computer to diffuse the encrypted block data output from said first processing unit with respect to a second portion of the encrypted block data which is wider than the first portion.

18. The article of manufacture according to

claim 17

, wherein

said first computer readable program code means performs a nonlinear transformation processing with respect to the encrypted block data in units of the first portions;

said second computer readable program code means performs a linear diffusion processing with respect to the second portion of the encrypted block data; and

said nonlinear transformation processing comprises;

a nonlinear transformation of the encrypted block data in units of the first portions; and

a linear diffusion of the second portion of the encrypted block data.

19. An method of decrypting encrypted block data, comprising:

randomizing the encrypted block data in units of first portions obtained by dividing the encrypted block data; and

diffusing the randomized encrypted block data with respect to a second portion of the encrypted block data which is wider than the first portion.

20. The method according to

claim 19

, wherein said randomizing comprises a nonlinear transformation of the encrypted block data in units of the first portions;

said diffusing comprises a linear diffusion of the second portion of the encrypted block data; and

said nonlinearly transformation comprises;

a nonlinear transformation of the encrypted block data in units of the first portions; and

a linear diffusion of the second portion of the encrypted block data.

21. An arithmetic operation device for a block data encryption apparatus which device diffuses block data using a Maximum Distance Separable matrix, the device comprising:

a multiplier configured to multiply corresponding bits of first portions obtained by dividing the block data and an element of the Maximum Distance Separable matrix without feeding back an overflow;

a lookup table configured to store data indicating a relation between predetermined upper bits and a return word for adjusting the overflow; and

an EX-OR circuit configured to read out the return word based on the predetermined upper bits and EX-OR the read return word and an output of the multiplier.