Encryption secured against DPA

• US 20030048903A1
• Filed: 12/28/2001
• Published: 03/13/2003
• Est. Priority Date: 06/13/2001
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Ito, Koichi, Takenaka, Masahiko, Torii, Naoya
• Granted Patent: US 7,386,130 B2
• Time in Patent Office: Days
• US Class Current: 380/263
• CPC Class Codes: H04L 2209/04 Masking or blinding
• CPC Class Codes: H04L 2209/12 Details relating to cryptographic hardware or logic circuitry
• CPC Class Codes: H04L 9/003 for power analysis, e.g. differential power analysis [DPA] or simple power analysis [SPA]

Abstract

The encryption device includes random number generator means for generating a random number; and a first selector for selecting one of q fixed values in response to the random number, a second selector for selecting one set of q sets of fixed tables in response to the random number. XOR means XORs an input with an XOR of a key with the fixed value. Nonlinear transform means nonlinearly transforms an input in accordance with the selected set of fixed table. Another encryption device includes a plurality of encrypting units coupled in parallel, and a selector for selecting one of the plurality of encrypting units in response to the random number. The masking with the fixed values improves of the processing speed and reduces the required RAM area.

Claims

1. An encryption device comprising XOR means and nonlinear transform means, said encryption device further comprising:

random number generator means for generating a random number;

q fixed values, where q is an integer; and

a first selector for selecting one of said q fixed values in response to the random number;

said XOR means XORing an input thereto with an XOR of a key with said selected fixed value.

2. The encryption device according to claim 1, further comprising:

q sets of masked fixed tables; and

a second selector for selecting one of said q sets of fixed tables in response to the random number,

said nonlinear transform means nonlinearly transforming an input thereto in accordance with the selected set of fixed tables.

3. The encryption device according to claim 1, further comprising:

an encrypting unit comprising said first XOR means and said nonlinear transform means;

second XOR means for XORing an input to said encryption device with a fixed value selected in response to the random number; and

third XOR means for XORing an output from said encrypting unit with the fixed value selected in response to the random number.

4. An encryption device comprising XOR means and nonlinear transform means, said encryption device further comprising:

random number generator means for generating a random number;

q sets of masked fixed tables, where q is an integer; and

a selector for selecting one of said q sets of fixed tables in response to the random number,

said nonlinear transform means nonlinearly transforming an input thereto in accordance with said selected set of fixed tables.

5. The encryption device according to claim 4, further comprising a plurality of encrypting rounds, wherein

each of said plurality of encrypting rounds comprises the XOR means, the fixed tables and the selector, for that round;

and

the fixed tables for said plurality of respective encrypting rounds are identical.

6. The encryption device according to claim 4, wherein

an equation, (c_0,j, XOR c_1,j)⊕

(c_1,j XOR c_2,j)⊕

. . . ⊕

(c<sub>q−

2,j</sub> XOR c<sub>q−

2,j</sub>)=(11111111)₂, is satisfied, where a fixed table before masking is defined as S[x], and a j-th masked table is defined as S_j[x XOR c_i,j] XOR d_i,j (j=0, 1, . . .

     15).

7. The encryption device according to claim 4, wherein

the number of sets of tables is q=2, and an equation, c_0,j XOR c_1,j=(10101010)₂ or (01010101)₂, is satisfied, where a fixed table before masking is defined as S[x], and a j-th masked table is defined as S_j[x XOR c_i,j] XOR d_i,j (j=0, 1, . . . 15).

8. The encryption device according to claim 4, wherein

an equation, (d_0,j XOR d_1,j)⊕

(d_1,j XOR d_2,j)⊕

. . . ⊕

(d<sub>q−

2,j</sub> XOR d<sub>q−

2,j</sub>)=(11111111)₂, is satisfied, where a fixed table before masking is defined as S[x], and a j-th masked table is defined as S_j[x XOR c_i,j] XOR d_i,j (j=0, 1, . . .

     15).

9. The encryption device according to claim 4, said nonlinear transform means being Subbyte means;

said encryption device further comprising means for shifting an input, and means for mixedcolumning an input.

10. An encryption device comprising:

random number generator means for generating a random number;

a plurality of encrypting units coupled in parallel; and

a selector for selecting one of said plurality of encrypting units in response to the random number;

each of said plurality of encrypting units comprises XOR means and nonlinear transform means.

11. The encryption device according to claim 10, wherein

said XOR means of said selected encrypting unit XORs an input thereto with an XOR of a key with a fixed value.

12. The encryption device according to claim 10, wherein

said nonlinear transform means nonlinearly transforms an input thereto in accordance with a fixed table.

13. The encryption device according to claim 10, wherein

each of said plurality of encrypting units comprises:

second XOR means for XORing an input thereto into that encrypting unit with a fixed value; and

third XOR means for producing an XOR of an input with a fixed value as an output from that encrypting unit.

14. The encryption device according to claim 10, wherein

said nonlinear transform means of said selected encrypting unit nonlinearly transforms an input thereto in accordance with a fixed table.

15. The encryption device according to claim 10, wherein

each of said plurality of encrypting units comprises a plurality of encrypting rounds;

each of said plurality of encrypting rounds comprises XOR means for XORing an input thereto with an XOR of a key with a fixed value, and nonlinear transform means for nonlinearly transforming an input thereto in accordance with a fixed table.

16. An encryption device comprising random number generator means for generating a random number and a first plurality of encrypting rounds, wherein

each of said plurality of encrypting rounds comprises nonlinear transform means for nonlinearly transforming an input thereto, and XOR means for XORing a first input thereto with a second input thereto;

the second input to said XOR means is coupled to an output of said nonlinear transform means; and

said nonlinear transform means comprises;

q fixed values, where q is an integer;

a selector for selecting one of said q fixed values in response to the random number; and

further XOR means for XORing an input thereto with an XOR of a key with said selected fixed value.

17. The encryption device according to claim 16, wherein

said nonlinear transform means further comprises therein a plurality of nonlinear transform means for nonlinearly transforming an input in accordance with a fixed table;

and a selector for selecting one of said plurality of nonlinear transform means.

18. The encryption device according to claim 17, wherein

the fixed tables of said respective nonlinear transform means in said respective encrypting rounds are identical.

19. The encryption device according to claim 16, wherein

a mask is canceled over subsequent ones of said plurality of encrypting rounds.

20. The encryption device according to claim 16, wherein

masking is performed in each of a second plurality of encrypting rounds of said first plurality of encrypting rounds, said second plurality being smaller than said first plurality.

21. An encryption device comprising a random number generator means for generating a random number, and a plurality of encrypting rounds, wherein

each of said plurality of encrypting rounds comprises nonlinear transform means for nonlinearly transforming an input thereto;

and XOR means for XORing a first input thereto and a second input thereto;

the second input to said XOR means is connected to an output of said nonlinear transform means; and

said nonlinear transform means comprises therein nonlinear transform means for nonlinearly transforming an input thereto in accordance with a fixed table and in accordance with the random number.

22. An encryption device, comprising:

random number generator means for generating a random number;

a plurality of encrypting units coupled in parallel; and

a selector for selecting one of said plurality of encrypting units in response to the random number, wherein,

each of said encrypting units comprises a plurality of encrypting rounds;

each of said encrypting rounds comprises;

nonlinear transform means for nonlinearly transforming an input thereto; and

XOR means for XORing a first input thereto with a second input thereto; and

the second input to said XOR means is coupled to an output of said nonlinear transform means.

23. The encryption device according to claim 22, wherein

said nonlinear transform means comprises:

further XOR means for XORing an input thereto with an XOR of a key with a fixed value; and

further nonlinear transform means for nonlinearly transforming an input thereto in accordance with a fixed table.

24. The encryption device according to claim 22, wherein

an equation, (d_0,j XOR d_1,j)⊕

(d_1,j XOR d_2,j)⊕

. . . ⊕

(d<sub>q−

2,j</sub> XOR d<sub>q−

2,j</sub>)=(1111)₂, is satisfied, where a fixed table before masking is defined as S_j[x], and a j-th masked table is defined as S_j′

[x XOR c_i,j] XOR d_i,j (j=0, 1, . . .

     7).

25. A program stored on a storage medium for use in an encryption device, said program operable to effect the steps of:

selecting one of q fixed values, where q is an integer, in response to a random number;

XORing an input value with an XOR of a key with said selected fixed value;

selecting one set of q sets of masked fixed tables in response to the random number; and

nonlinearly transforming an input value in accordance with said selected set of fixed tables.

26. A program stored on a storage medium for use in an encryption device, said program operable to effect the steps of:

selecting one of a plurality of encryption processes in response to a random number, and

encrypting an input value in accordance with said selected encryption process to provide an output;

the encrypting step comprising the steps of;

XORing an input value with an XOR of a key with a fixed value, and

nonlinear transforming an input value in accordance with a set of fixed tables.

27. A program stored on a storage medium for use in an encryption device, said program operable to effect the steps of:

nonlinear transforming an input value to provide an output, and

XORing a first input value with said output as a second input value;

the nonlinear transforming step comprising the steps of;

selecting one of q fixed values in response to a random number, where q is an integer,

XORing an input value with an XOR of a key with said selected fixed value, and

nonlinear transforming an input value in accordance with a set of fixed tables associated with the random number.

28. A program stored on a storage medium for use in an encryption device, said program operable to effect the steps of:

selecting one of a plurality of encryption processes in response to a random number, and

encrypting an input value in accordance with said selected encryption processes to provide an output;

the encrypting step comprising the steps of;

nonlinear transforming an input value to produce an output, and

XORing a first input value with said output as a second input value.