diff options
| author | Stefan Berger | 2024-04-04 10:18:49 -0400 |
|---|---|---|
| committer | Herbert Xu | 2024-04-12 15:07:52 +0800 |
| commit | e7fb062754ef9f656ee004f2be8f59ce8a79bffb (patch) | |
| tree | 1f93573ef86eb6e7133dd14d5e6e90ceb94f3fa7 /crypto/ecc.c | |
| parent | c0d6bd1fd367a5374bff7e3f3bdf47beb84893c8 (diff) | |
crypto: ecc - Implement vli_mmod_fast_521 for NIST p521
Implement vli_mmod_fast_521 following the description for how to calculate
the modulus for NIST P521 in the NIST publication "Recommendations for
Discrete Logarithm-Based Cryptography: Elliptic Curve Domain Parameters"
section G.1.4.
NIST p521 requires 9 64bit digits, so increase the ECC_MAX_DIGITS so that
the vli digit array provides enough elements to fit the larger integers
required by this curve.
Tested-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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; |