diff options
Diffstat (limited to 'crypto/ecc.c')
| -rw-r--r-- | crypto/ecc.c | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/crypto/ecc.c b/crypto/ecc.c index e94183f6c418..8914e437f94b 100644 --- a/crypto/ecc.c +++ b/crypto/ecc.c @@ -902,6 +902,28 @@ static void vli_mmod_fast_384(u64 *result, const u64 *product, #undef AND64H #undef AND64L +/* + * Computes result = product % curve_prime + * from "Recommendations for Discrete Logarithm-Based Cryptography: + * Elliptic Curve Domain Parameters" section G.1.4 + */ +static void vli_mmod_fast_521(u64 *result, const u64 *product, + const u64 *curve_prime, u64 *tmp) +{ + const unsigned int ndigits = ECC_CURVE_NIST_P521_DIGITS; + size_t i; + + /* Initialize result with lowest 521 bits from product */ + vli_set(result, product, ndigits); + result[8] &= 0x1ff; + + for (i = 0; i < ndigits; i++) + tmp[i] = (product[8 + i] >> 9) | (product[9 + i] << 55); + tmp[8] &= 0x1ff; + + vli_mod_add(result, result, tmp, curve_prime, ndigits); +} + /* Computes result = product % curve_prime for different curve_primes. * * Note that curve_primes are distinguished just by heuristic check and @@ -941,6 +963,9 @@ static bool vli_mmod_fast(u64 *result, u64 *product, case ECC_CURVE_NIST_P384_DIGITS: vli_mmod_fast_384(result, product, curve_prime, tmp); break; + case ECC_CURVE_NIST_P521_DIGITS: + vli_mmod_fast_521(result, product, curve_prime, tmp); + break; default: pr_err_ratelimited("ecc: unsupported digits size!\n"); return false; |