Messages in this thread | | | Date | Mon, 11 Mar 2024 10:03:07 -0400 | From | Stefan Berger <> | Subject | Re: [PATCH v5 05/12] crypto: ecc - Implement vli_mmod_fast_521 for NIST p521 |
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On 3/11/24 01:07, Bharat Bhushan wrote: > Minor nits > >> -----Original Message----- >> From: Stefan Berger <stefanb@linux.ibm.com> >> Sent: Thursday, March 7, 2024 3:53 AM >> To: keyrings@vger.kernel.org; linux-crypto@vger.kernel.org; >> herbert@gondor.apana.org.au; davem@davemloft.net >> Cc: linux-kernel@vger.kernel.org; saulo.alessandre@tse.jus.br; >> lukas@wunner.de; Stefan Berger <stefanb@linux.ibm.com> >> Subject: [EXTERNAL] [PATCH v5 05/12] 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 >> arrays fit the larger numbers. >> >> Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> >> Tested-by: Lukas Wunner <lukas@wunner.de> >> --- >> crypto/ecc.c | 31 +++++++++++++++++++++++++++++++ >> include/crypto/internal/ecc.h | 2 +- >> 2 files changed, 32 insertions(+), 1 deletion(-) >> >> diff --git a/crypto/ecc.c b/crypto/ecc.c index f53fb4d6af99..373660e7b19d >> 100644 >> --- a/crypto/ecc.c >> +++ b/crypto/ecc.c >> @@ -902,6 +902,31 @@ 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" G.1.4 >> + */ >> +static void vli_mmod_fast_521(u64 *result, const u64 *product, >> + const u64 *curve_prime, u64 *tmp) >> +{ >> + const unsigned int ndigits = 9; >> + size_t i; >> + >> + for (i = 0; i < ndigits; i++) >> + tmp[i] = product[i]; >> + tmp[8] &= 0x1ff; >> + >> + vli_set(result, tmp, ndigits);
I have also modified this here now to initialize 'result' from lowest 521 bis of product without the detour through tmp.
>> + >> + >> + 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 +966,12 @@ static bool vli_mmod_fast(u64 *result, u64 *product, >> case 6: >> vli_mmod_fast_384(result, product, curve_prime, tmp); >> break; >> + case 9: > > Can we use ECC_CURVE_NIST_P384_DIGITS, ECC_CURVE_NIST_P256_DIGITS in this function? > > And define ECC_CURVE_NIST_P521_DIGITS, which is same as ECC_MAX_DIGITS defined below in this patch? > >> + if (curve->nbits == 521) {
If I replace the numbers with these hash-defines's in here (in an additional patch on existing code) then I can just about remove the check on nbits here as well... ?
>> + vli_mmod_fast_521(result, product, curve_prime, >> tmp); >> + break; >> + } >> + fallthrough; >> default: >> pr_err_ratelimited("ecc: unsupported digits size!\n"); >> return false; >> diff --git a/include/crypto/internal/ecc.h b/include/crypto/internal/ecc.h index >> 4a556b41873e..de17bcdeb53a 100644 >> --- a/include/crypto/internal/ecc.h >> +++ b/include/crypto/internal/ecc.h >> @@ -33,7 +33,7 @@ >> #define ECC_CURVE_NIST_P192_DIGITS 3 >> #define ECC_CURVE_NIST_P256_DIGITS 4 >> #define ECC_CURVE_NIST_P384_DIGITS 6 >> -#define ECC_MAX_DIGITS (512 / 64) /* due to ecrdsa */ >> +#define ECC_MAX_DIGITS DIV_ROUND_UP(521, 64) /* NIST P521 */ >> >> #define ECC_DIGITS_TO_BYTES_SHIFT 3 >> >> -- >> 2.43.0 >> >
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