| US 7,512,231 B2 | ||
| Computation method for modular exponentiation operation in decryption or signature generation | ||
| Katsuyuki Okeya, Yokohama (Japan); and Tsuyoshi Takagi, Hofheim-Wallau (Germany) | ||
| Assigned to Hitachi, Ltd., Tokyo (Japan) | ||
| Filed on Jul. 19, 2004, as Appl. No. 10/893,523. | ||
| Claims priority of application No. 2004-001602 (JP), filed on Jan. 07, 2004. | ||
| Prior Publication US 2005/0147241 A1, Jul. 07, 2005 | ||
| Int. Cl. H04L 9/28 (2006.01) | ||
| U.S. Cl. 380—28 | 8 Claims |
| 5. A signature generation method of generating signature data m from a secret exponent d, a public key n, and data c in a
digital signature using a public-key cryptosystem, said method comprising steps executed by a computer, said steps comprising:
(i) converting the data c into randomized data t,
(ii) converting the randomized data t into a randomized signature u, and
(iii) converting the randomized signature u into the signature data m,
wherein said step (i) of converting the data c into the randomized data t comprises: generating a random number r, and using
the random number r and an integer s derived from the random number r,
wherein said step (ii) of converting the randomized data t into the randomized signature u comprises: computing the randomized
signature u by using a value derived from the secret exponent d,
wherein said step (iii) of converting the randomized signature u into the signature data m comprises multiplying the randomized
signature u by the integer s,
wherein re−1 is used as the integer s derived from the random number r, where e is a public exponent, and
wherein said step of converting into the randomized data t comprises multiplying the data c by sr.
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