diff options
| -rw-r--r-- | hashsig.c | 63 |
1 files changed, 23 insertions, 40 deletions
@@ -137,21 +137,15 @@ static inline hal_error_t hal_xdr_decode_bytestring16(const uint8_t ** const inb * LM-OTS */ -static uint8_t coef1(const uint8_t * const S, const size_t i); -static uint8_t coef2(const uint8_t * const S, const size_t i); -static uint8_t coef4(const uint8_t * const S, const size_t i); -static uint8_t coef8(const uint8_t * const S, const size_t i); - typedef const struct lmots_parameter_set { lmots_algorithm_t type; size_t n, w, w2, p, ls; - uint8_t (*coef)(const uint8_t * const S, const size_t i); } lmots_parameter_t; static lmots_parameter_t lmots_parameters[] = { - { lmots_sha256_n32_w1, 32, 1, 2, 265, 7, coef1 }, - { lmots_sha256_n32_w2, 32, 2, 4, 133, 6, coef2 }, - { lmots_sha256_n32_w4, 32, 4, 16, 67, 4, coef4 }, - { lmots_sha256_n32_w8, 32, 8, 256, 34, 0, coef8 }, + { lmots_sha256_n32_w1, 32, 1, 2, 265, 7 }, + { lmots_sha256_n32_w2, 32, 2, 4, 133, 6 }, + { lmots_sha256_n32_w4, 32, 4, 16, 67, 4 }, + { lmots_sha256_n32_w8, 32, 8, 256, 34, 0 }, }; typedef struct lmots_key { @@ -265,32 +259,21 @@ static hal_error_t lmots_generate(lmots_key_t * const key) } #endif -/* coef() functions for the supported values of w. - * This is a bit of premature optimization, because coef() gets called a lot. - */ - -/* w = 1 */ -static uint8_t coef1(const uint8_t * const S, const size_t i) -{ - return (S[i/8] >> (7 - (i % 8))) & 0x01; -} - -/* w = 2 */ -static uint8_t coef2(const uint8_t * const S, const size_t i) -{ - return (S[i/4] >> (6 - (2 * (i % 4)))) & 0x03; -} - -/* w = 4 */ -static uint8_t coef4(const uint8_t * const S, const size_t i) +/* strings of w-bit elements */ +static uint8_t coef(const uint8_t * const S, const size_t i, size_t w) { - return (S[i/2] >> (4 - (4 * (i % 2)))) & 0x0f; -} - -/* w = 8 */ -static uint8_t coef8(const uint8_t * const S, const size_t i) -{ - return S[i]; + switch (w) { + case 1: + return (S[i/8] >> (7 - (i % 8))) & 0x01; + case 2: + return (S[i/4] >> (6 - (2 * (i % 4)))) & 0x03; + case 4: + return (S[i/2] >> (4 - (4 * (i % 2)))) & 0x0f; + case 8: + return S[i]; + default: + return 0; + } } /* checksum */ @@ -299,7 +282,7 @@ static uint16_t Cksm(const uint8_t * const S, lmots_parameter_t *lmots) uint16_t sum = 0; for (size_t i = 0; i < (lmots->n * 8 / lmots->w); ++i) - sum += (lmots->w2 - 1) - lmots->coef(S, i); + sum += (lmots->w2 - 1) - coef(S, i, lmots->w); return (sum << lmots->ls); } @@ -321,7 +304,7 @@ static hal_error_t lmots_sign(lmots_key_t *key, size_t n = key->lmots->n; size_t p = key->lmots->p; - uint8_t (*coef)() = key->lmots->coef; + size_t w = key->lmots->w; if (sig_max < lmots_signature_len(key->lmots)) return HAL_ERROR_BAD_ARGUMENTS; @@ -360,7 +343,7 @@ static hal_error_t lmots_sign(lmots_key_t *key, for (size_t i = 0; i < p; ++i) { // a = coef(Q || Cksm(Q), i, w) - uint8_t a = coef(Q, i); + uint8_t a = coef(Q, i, w); // tmp = x[i] bytestring32 tmp; @@ -431,8 +414,8 @@ static hal_error_t lmots_public_key_candidate(const lmots_key_t * const key, size_t n = key->lmots->n; size_t p = key->lmots->p; + size_t w = key->lmots->w; size_t w2 = key->lmots->w2; - uint8_t (*coef)() = key->lmots->coef; // d. C = next n bytes of signature @@ -475,7 +458,7 @@ static hal_error_t lmots_public_key_candidate(const lmots_key_t * const key, for (size_t i = 0; i < p; ++i) { // a = coef(Q || Cksm(Q), i, w) - uint8_t a = coef(Q, i); + uint8_t a = coef(Q, i, w); // tmp = y[i] bytestring32 tmp; |