micro-ECC for mbed, ported from GCC version from Github,
Dependents: mbed_microECC Wallet_v1
Diff: uECC.cpp
- Revision:
- 0:b6fdeddc0bc9
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/uECC.cpp Thu Sep 07 12:10:11 2017 +0000 @@ -0,0 +1,1644 @@ +/* Copyright 2014, Kenneth MacKay. Licensed under the BSD 2-clause license. */ + +#include "uECC.h" +#include "uECC_vli.h" + +#ifndef uECC_RNG_MAX_TRIES + #define uECC_RNG_MAX_TRIES 64 +#endif + +#if uECC_ENABLE_VLI_API + #define uECC_VLI_API +#else + #define uECC_VLI_API static +#endif + +#define CONCATX(a, ...) a ## __VA_ARGS__ +#define CONCAT(a, ...) CONCATX(a, __VA_ARGS__) + +#define STRX(a) #a +#define STR(a) STRX(a) + +#define EVAL(...) EVAL1(EVAL1(EVAL1(EVAL1(__VA_ARGS__)))) +#define EVAL1(...) EVAL2(EVAL2(EVAL2(EVAL2(__VA_ARGS__)))) +#define EVAL2(...) EVAL3(EVAL3(EVAL3(EVAL3(__VA_ARGS__)))) +#define EVAL3(...) EVAL4(EVAL4(EVAL4(EVAL4(__VA_ARGS__)))) +#define EVAL4(...) __VA_ARGS__ + +#define DEC_1 0 +#define DEC_2 1 +#define DEC_3 2 +#define DEC_4 3 +#define DEC_5 4 +#define DEC_6 5 +#define DEC_7 6 +#define DEC_8 7 +#define DEC_9 8 +#define DEC_10 9 +#define DEC_11 10 +#define DEC_12 11 +#define DEC_13 12 +#define DEC_14 13 +#define DEC_15 14 +#define DEC_16 15 +#define DEC_17 16 +#define DEC_18 17 +#define DEC_19 18 +#define DEC_20 19 +#define DEC_21 20 +#define DEC_22 21 +#define DEC_23 22 +#define DEC_24 23 +#define DEC_25 24 +#define DEC_26 25 +#define DEC_27 26 +#define DEC_28 27 +#define DEC_29 28 +#define DEC_30 29 +#define DEC_31 30 +#define DEC_32 31 + +#define DEC(N) CONCAT(DEC_, N) + +#define SECOND_ARG(_, val, ...) val +#define SOME_CHECK_0 ~, 0 +#define GET_SECOND_ARG(...) SECOND_ARG(__VA_ARGS__, SOME,) +#define SOME_OR_0(N) GET_SECOND_ARG(CONCAT(SOME_CHECK_, N)) + +#define EMPTY(...) +#define DEFER(...) __VA_ARGS__ EMPTY() + +#define REPEAT_NAME_0() REPEAT_0 +#define REPEAT_NAME_SOME() REPEAT_SOME +#define REPEAT_0(...) +#define REPEAT_SOME(N, stuff) DEFER(CONCAT(REPEAT_NAME_, SOME_OR_0(DEC(N))))()(DEC(N), stuff) stuff +#define REPEAT(N, stuff) EVAL(REPEAT_SOME(N, stuff)) + +#define REPEATM_NAME_0() REPEATM_0 +#define REPEATM_NAME_SOME() REPEATM_SOME +#define REPEATM_0(...) +#define REPEATM_SOME(N, macro) macro(N) \ + DEFER(CONCAT(REPEATM_NAME_, SOME_OR_0(DEC(N))))()(DEC(N), macro) +#define REPEATM(N, macro) EVAL(REPEATM_SOME(N, macro)) + +//#include "platform-specific.inc" +#include "platform-specific.h" + +#if (uECC_WORD_SIZE == 1) + #if uECC_SUPPORTS_secp160r1 + #define uECC_MAX_WORDS 21 /* Due to the size of curve_n. */ + #endif + #if uECC_SUPPORTS_secp192r1 + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 24 + #endif + #if uECC_SUPPORTS_secp224r1 + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 28 + #endif + #if (uECC_SUPPORTS_secp256r1 || uECC_SUPPORTS_secp256k1) + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 32 + #endif +#elif (uECC_WORD_SIZE == 4) + #if uECC_SUPPORTS_secp160r1 + #define uECC_MAX_WORDS 6 /* Due to the size of curve_n. */ + #endif + #if uECC_SUPPORTS_secp192r1 + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 6 + #endif + #if uECC_SUPPORTS_secp224r1 + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 7 + #endif + #if (uECC_SUPPORTS_secp256r1 || uECC_SUPPORTS_secp256k1) + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 8 + #endif +#elif (uECC_WORD_SIZE == 8) + #if uECC_SUPPORTS_secp160r1 + #define uECC_MAX_WORDS 3 + #endif + #if uECC_SUPPORTS_secp192r1 + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 3 + #endif + #if uECC_SUPPORTS_secp224r1 + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 4 + #endif + #if (uECC_SUPPORTS_secp256r1 || uECC_SUPPORTS_secp256k1) + #undef uECC_MAX_WORDS + #define uECC_MAX_WORDS 4 + #endif +#endif /* uECC_WORD_SIZE */ + +#define BITS_TO_WORDS(num_bits) ((num_bits + ((uECC_WORD_SIZE * 8) - 1)) / (uECC_WORD_SIZE * 8)) +#define BITS_TO_BYTES(num_bits) ((num_bits + 7) / 8) + +struct uECC_Curve_t { + wordcount_t num_words; + wordcount_t num_bytes; + bitcount_t num_n_bits; + uECC_word_t p[uECC_MAX_WORDS]; + uECC_word_t n[uECC_MAX_WORDS]; + uECC_word_t G[uECC_MAX_WORDS * 2]; + uECC_word_t b[uECC_MAX_WORDS]; + void (*double_jacobian)(uECC_word_t * X1, + uECC_word_t * Y1, + uECC_word_t * Z1, + uECC_Curve curve); +#if uECC_SUPPORT_COMPRESSED_POINT + void (*mod_sqrt)(uECC_word_t *a, uECC_Curve curve); +#endif + void (*x_side)(uECC_word_t *result, const uECC_word_t *x, uECC_Curve curve); +#if (uECC_OPTIMIZATION_LEVEL > 0) + void (*mmod_fast)(uECC_word_t *result, uECC_word_t *product); +#endif +}; + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN +static void bcopy(uint8_t *dst, + const uint8_t *src, + unsigned num_bytes) { + while (0 != num_bytes) { + num_bytes--; + dst[num_bytes] = src[num_bytes]; + } +} +#endif + +static cmpresult_t uECC_vli_cmp_unsafe(const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words); + +#if (uECC_PLATFORM == uECC_arm || uECC_PLATFORM == uECC_arm_thumb || \ + uECC_PLATFORM == uECC_arm_thumb2) + //#include "asm_arm.inc" + #include "asm_arm.h" +#if (uECC_PLATFORM == uECC_arm) + #warning uECC_arm +#elif (uECC_PLATFORM == uECC_arm_thumb) + #warning uECC_arm_thumb +#elif (uECC_PLATFORM == uECC_arm_thumb2) + #warning uECC_arm_thumb2 +#endif +#endif + +#if (uECC_PLATFORM == uECC_avr) + #include "asm_avr.inc" +#endif + +#if default_RNG_defined +static uECC_RNG_Function g_rng_function = &default_RNG; +#else +static uECC_RNG_Function g_rng_function = 0; +#endif + +void uECC_set_rng(uECC_RNG_Function rng_function) { + g_rng_function = rng_function; +} + +uECC_RNG_Function uECC_get_rng(void) { + return g_rng_function; +} + +int uECC_curve_private_key_size(uECC_Curve curve) { + return BITS_TO_BYTES(curve->num_n_bits); +} + +int uECC_curve_public_key_size(uECC_Curve curve) { + return 2 * curve->num_bytes; +} + +#if !asm_clear +uECC_VLI_API void uECC_vli_clear(uECC_word_t *vli, wordcount_t num_words) { + wordcount_t i; + for (i = 0; i < num_words; ++i) { + vli[i] = 0; + } +} +#endif /* !asm_clear */ + +/* Constant-time comparison to zero - secure way to compare long integers */ +/* Returns 1 if vli == 0, 0 otherwise. */ +uECC_VLI_API uECC_word_t uECC_vli_isZero(const uECC_word_t *vli, wordcount_t num_words) { + uECC_word_t bits = 0; + wordcount_t i; + for (i = 0; i < num_words; ++i) { + bits |= vli[i]; + } + return (bits == 0); +} + +/* Returns nonzero if bit 'bit' of vli is set. */ +uECC_VLI_API uECC_word_t uECC_vli_testBit(const uECC_word_t *vli, bitcount_t bit) { + return (vli[bit >> uECC_WORD_BITS_SHIFT] & ((uECC_word_t)1 << (bit & uECC_WORD_BITS_MASK))); +} + +/* Counts the number of words in vli. */ +static wordcount_t vli_numDigits(const uECC_word_t *vli, const wordcount_t max_words) { + wordcount_t i; + /* Search from the end until we find a non-zero digit. + We do it in reverse because we expect that most digits will be nonzero. */ + for (i = max_words - 1; i >= 0 && vli[i] == 0; --i) { + } + + return (i + 1); +} + +/* Counts the number of bits required to represent vli. */ +uECC_VLI_API bitcount_t uECC_vli_numBits(const uECC_word_t *vli, const wordcount_t max_words) { + uECC_word_t i; + uECC_word_t digit; + + wordcount_t num_digits = vli_numDigits(vli, max_words); + if (num_digits == 0) { + return 0; + } + + digit = vli[num_digits - 1]; + for (i = 0; digit; ++i) { + digit >>= 1; + } + + return (((bitcount_t)(num_digits - 1) << uECC_WORD_BITS_SHIFT) + i); +} + +/* Sets dest = src. */ +#if !asm_set +uECC_VLI_API void uECC_vli_set(uECC_word_t *dest, const uECC_word_t *src, wordcount_t num_words) { + wordcount_t i; + for (i = 0; i < num_words; ++i) { + dest[i] = src[i]; + } +} +#endif /* !asm_set */ + +/* Returns sign of left - right. */ +static cmpresult_t uECC_vli_cmp_unsafe(const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words) { + wordcount_t i; + for (i = num_words - 1; i >= 0; --i) { + if (left[i] > right[i]) { + return 1; + } else if (left[i] < right[i]) { + return -1; + } + } + return 0; +} + +/* Constant-time comparison function - secure way to compare long integers */ +/* Returns one if left == right, zero otherwise. */ +uECC_VLI_API uECC_word_t uECC_vli_equal(const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words) { + uECC_word_t diff = 0; + wordcount_t i; + for (i = num_words - 1; i >= 0; --i) { + diff |= (left[i] ^ right[i]); + } + return (diff == 0); +} + +uECC_VLI_API uECC_word_t uECC_vli_sub(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words); + +/* Returns sign of left - right, in constant time. */ +uECC_VLI_API cmpresult_t uECC_vli_cmp(const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words) { + uECC_word_t tmp[uECC_MAX_WORDS]; + uECC_word_t neg = !!uECC_vli_sub(tmp, left, right, num_words); + uECC_word_t equal = uECC_vli_isZero(tmp, num_words); + return (!equal - 2 * neg); +} + +/* Computes vli = vli >> 1. */ +#if !asm_rshift1 +uECC_VLI_API void uECC_vli_rshift1(uECC_word_t *vli, wordcount_t num_words) { + uECC_word_t *end = vli; + uECC_word_t carry = 0; + + vli += num_words; + while (vli-- > end) { + uECC_word_t temp = *vli; + *vli = (temp >> 1) | carry; + carry = temp << (uECC_WORD_BITS - 1); + } +} +#endif /* !asm_rshift1 */ + +/* Computes result = left + right, returning carry. Can modify in place. */ +#if !asm_add +uECC_VLI_API uECC_word_t uECC_vli_add(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words) { + uECC_word_t carry = 0; + wordcount_t i; + for (i = 0; i < num_words; ++i) { + uECC_word_t sum = left[i] + right[i] + carry; + if (sum != left[i]) { + carry = (sum < left[i]); + } + result[i] = sum; + } + return carry; +} +#endif /* !asm_add */ + +/* Computes result = left - right, returning borrow. Can modify in place. */ +#if !asm_sub +uECC_VLI_API uECC_word_t uECC_vli_sub(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words) { + uECC_word_t borrow = 0; + wordcount_t i; + for (i = 0; i < num_words; ++i) { + uECC_word_t diff = left[i] - right[i] - borrow; + if (diff != left[i]) { + borrow = (diff > left[i]); + } + result[i] = diff; + } + return borrow; +} +#endif /* !asm_sub */ + +#if !asm_mult || (uECC_SQUARE_FUNC && !asm_square) || \ + (uECC_SUPPORTS_secp256k1 && (uECC_OPTIMIZATION_LEVEL > 0) && \ + ((uECC_WORD_SIZE == 1) || (uECC_WORD_SIZE == 8))) +static void muladd(uECC_word_t a, + uECC_word_t b, + uECC_word_t *r0, + uECC_word_t *r1, + uECC_word_t *r2) { +#if uECC_WORD_SIZE == 8 && !SUPPORTS_INT128 + uint64_t a0 = a & 0xffffffffull; + uint64_t a1 = a >> 32; + uint64_t b0 = b & 0xffffffffull; + uint64_t b1 = b >> 32; + + uint64_t i0 = a0 * b0; + uint64_t i1 = a0 * b1; + uint64_t i2 = a1 * b0; + uint64_t i3 = a1 * b1; + + uint64_t p0, p1; + + i2 += (i0 >> 32); + i2 += i1; + if (i2 < i1) { /* overflow */ + i3 += 0x100000000ull; + } + + p0 = (i0 & 0xffffffffull) | (i2 << 32); + p1 = i3 + (i2 >> 32); + + *r0 += p0; + *r1 += (p1 + (*r0 < p0)); + *r2 += ((*r1 < p1) || (*r1 == p1 && *r0 < p0)); +#else + uECC_dword_t p = (uECC_dword_t)a * b; + uECC_dword_t r01 = ((uECC_dword_t)(*r1) << uECC_WORD_BITS) | *r0; + r01 += p; + *r2 += (r01 < p); + *r1 = r01 >> uECC_WORD_BITS; + *r0 = (uECC_word_t)r01; +#endif +} +#endif /* muladd needed */ + +#if !asm_mult +uECC_VLI_API void uECC_vli_mult(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + wordcount_t num_words) { + uECC_word_t r0 = 0; + uECC_word_t r1 = 0; + uECC_word_t r2 = 0; + wordcount_t i, k; + + /* Compute each digit of result in sequence, maintaining the carries. */ + for (k = 0; k < num_words; ++k) { + for (i = 0; i <= k; ++i) { + muladd(left[i], right[k - i], &r0, &r1, &r2); + } + result[k] = r0; + r0 = r1; + r1 = r2; + r2 = 0; + } + for (k = num_words; k < num_words * 2 - 1; ++k) { + for (i = (k + 1) - num_words; i < num_words; ++i) { + muladd(left[i], right[k - i], &r0, &r1, &r2); + } + result[k] = r0; + r0 = r1; + r1 = r2; + r2 = 0; + } + result[num_words * 2 - 1] = r0; +} +#endif /* !asm_mult */ + +#if uECC_SQUARE_FUNC + +#if !asm_square +static void mul2add(uECC_word_t a, + uECC_word_t b, + uECC_word_t *r0, + uECC_word_t *r1, + uECC_word_t *r2) { +#if uECC_WORD_SIZE == 8 && !SUPPORTS_INT128 + uint64_t a0 = a & 0xffffffffull; + uint64_t a1 = a >> 32; + uint64_t b0 = b & 0xffffffffull; + uint64_t b1 = b >> 32; + + uint64_t i0 = a0 * b0; + uint64_t i1 = a0 * b1; + uint64_t i2 = a1 * b0; + uint64_t i3 = a1 * b1; + + uint64_t p0, p1; + + i2 += (i0 >> 32); + i2 += i1; + if (i2 < i1) + { /* overflow */ + i3 += 0x100000000ull; + } + + p0 = (i0 & 0xffffffffull) | (i2 << 32); + p1 = i3 + (i2 >> 32); + + *r2 += (p1 >> 63); + p1 = (p1 << 1) | (p0 >> 63); + p0 <<= 1; + + *r0 += p0; + *r1 += (p1 + (*r0 < p0)); + *r2 += ((*r1 < p1) || (*r1 == p1 && *r0 < p0)); +#else + uECC_dword_t p = (uECC_dword_t)a * b; + uECC_dword_t r01 = ((uECC_dword_t)(*r1) << uECC_WORD_BITS) | *r0; + *r2 += (p >> (uECC_WORD_BITS * 2 - 1)); + p *= 2; + r01 += p; + *r2 += (r01 < p); + *r1 = r01 >> uECC_WORD_BITS; + *r0 = (uECC_word_t)r01; +#endif +} + +uECC_VLI_API void uECC_vli_square(uECC_word_t *result, + const uECC_word_t *left, + wordcount_t num_words) { + uECC_word_t r0 = 0; + uECC_word_t r1 = 0; + uECC_word_t r2 = 0; + + wordcount_t i, k; + + for (k = 0; k < num_words * 2 - 1; ++k) { + uECC_word_t min = (k < num_words ? 0 : (k + 1) - num_words); + for (i = min; i <= k && i <= k - i; ++i) { + if (i < k-i) { + mul2add(left[i], left[k - i], &r0, &r1, &r2); + } else { + muladd(left[i], left[k - i], &r0, &r1, &r2); + } + } + result[k] = r0; + r0 = r1; + r1 = r2; + r2 = 0; + } + + result[num_words * 2 - 1] = r0; +} +#endif /* !asm_square */ + +#else /* uECC_SQUARE_FUNC */ + +#if uECC_ENABLE_VLI_API +uECC_VLI_API void uECC_vli_square(uECC_word_t *result, + const uECC_word_t *left, + wordcount_t num_words) { + uECC_vli_mult(result, left, left, num_words); +} +#endif /* uECC_ENABLE_VLI_API */ + +#endif /* uECC_SQUARE_FUNC */ + +/* Computes result = (left + right) % mod. + Assumes that left < mod and right < mod, and that result does not overlap mod. */ +uECC_VLI_API void uECC_vli_modAdd(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t carry = uECC_vli_add(result, left, right, num_words); + if (carry || uECC_vli_cmp_unsafe(mod, result, num_words) != 1) { + /* result > mod (result = mod + remainder), so subtract mod to get remainder. */ + uECC_vli_sub(result, result, mod, num_words); + } +} + +/* Computes result = (left - right) % mod. + Assumes that left < mod and right < mod, and that result does not overlap mod. */ +uECC_VLI_API void uECC_vli_modSub(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t l_borrow = uECC_vli_sub(result, left, right, num_words); + if (l_borrow) { + /* In this case, result == -diff == (max int) - diff. Since -x % d == d - x, + we can get the correct result from result + mod (with overflow). */ + uECC_vli_add(result, result, mod, num_words); + } +} + +/* Computes result = product % mod, where product is 2N words long. */ +/* Currently only designed to work for curve_p or curve_n. */ +uECC_VLI_API void uECC_vli_mmod(uECC_word_t *result, + uECC_word_t *product, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t mod_multiple[2 * uECC_MAX_WORDS]; + uECC_word_t tmp[2 * uECC_MAX_WORDS]; + uECC_word_t *v[2] = {tmp, product}; + uECC_word_t index; + + /* Shift mod so its highest set bit is at the maximum position. */ + bitcount_t shift = (num_words * 2 * uECC_WORD_BITS) - uECC_vli_numBits(mod, num_words); + wordcount_t word_shift = shift / uECC_WORD_BITS; + wordcount_t bit_shift = shift % uECC_WORD_BITS; + uECC_word_t carry = 0; + uECC_vli_clear(mod_multiple, word_shift); + if (bit_shift > 0) { + for(index = 0; index < (uECC_word_t)num_words; ++index) { + mod_multiple[word_shift + index] = (mod[index] << bit_shift) | carry; + carry = mod[index] >> (uECC_WORD_BITS - bit_shift); + } + } else { + uECC_vli_set(mod_multiple + word_shift, mod, num_words); + } + + for (index = 1; shift >= 0; --shift) { + uECC_word_t borrow = 0; + wordcount_t i; + for (i = 0; i < num_words * 2; ++i) { + uECC_word_t diff = v[index][i] - mod_multiple[i] - borrow; + if (diff != v[index][i]) { + borrow = (diff > v[index][i]); + } + v[1 - index][i] = diff; + } + index = !(index ^ borrow); /* Swap the index if there was no borrow */ + uECC_vli_rshift1(mod_multiple, num_words); + mod_multiple[num_words - 1] |= mod_multiple[num_words] << (uECC_WORD_BITS - 1); + uECC_vli_rshift1(mod_multiple + num_words, num_words); + } + uECC_vli_set(result, v[index], num_words); +} + +/* Computes result = (left * right) % mod. */ +uECC_VLI_API void uECC_vli_modMult(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t product[2 * uECC_MAX_WORDS]; + uECC_vli_mult(product, left, right, num_words); + uECC_vli_mmod(result, product, mod, num_words); +} + +uECC_VLI_API void uECC_vli_modMult_fast(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *right, + uECC_Curve curve) { + uECC_word_t product[2 * uECC_MAX_WORDS]; + uECC_vli_mult(product, left, right, curve->num_words); +#if (uECC_OPTIMIZATION_LEVEL > 0) + curve->mmod_fast(result, product); +#else + uECC_vli_mmod(result, product, curve->p, curve->num_words); +#endif +} + +#if uECC_SQUARE_FUNC + +#if uECC_ENABLE_VLI_API +/* Computes result = left^2 % mod. */ +uECC_VLI_API void uECC_vli_modSquare(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t product[2 * uECC_MAX_WORDS]; + uECC_vli_square(product, left, num_words); + uECC_vli_mmod(result, product, mod, num_words); +} +#endif /* uECC_ENABLE_VLI_API */ + +uECC_VLI_API void uECC_vli_modSquare_fast(uECC_word_t *result, + const uECC_word_t *left, + uECC_Curve curve) { + uECC_word_t product[2 * uECC_MAX_WORDS]; + uECC_vli_square(product, left, curve->num_words); +#if (uECC_OPTIMIZATION_LEVEL > 0) + curve->mmod_fast(result, product); +#else + uECC_vli_mmod(result, product, curve->p, curve->num_words); +#endif +} + +#else /* uECC_SQUARE_FUNC */ + +#if uECC_ENABLE_VLI_API +uECC_VLI_API void uECC_vli_modSquare(uECC_word_t *result, + const uECC_word_t *left, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_vli_modMult(result, left, left, mod, num_words); +} +#endif /* uECC_ENABLE_VLI_API */ + +uECC_VLI_API void uECC_vli_modSquare_fast(uECC_word_t *result, + const uECC_word_t *left, + uECC_Curve curve) { + uECC_vli_modMult_fast(result, left, left, curve); +} + +#endif /* uECC_SQUARE_FUNC */ + +#define EVEN(vli) (!(vli[0] & 1)) +static void vli_modInv_update(uECC_word_t *uv, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t carry = 0; + if (!EVEN(uv)) { + carry = uECC_vli_add(uv, uv, mod, num_words); + } + uECC_vli_rshift1(uv, num_words); + if (carry) { + uv[num_words - 1] |= HIGH_BIT_SET; + } +} + +/* Computes result = (1 / input) % mod. All VLIs are the same size. + See "From Euclid's GCD to Montgomery Multiplication to the Great Divide" */ +uECC_VLI_API void uECC_vli_modInv(uECC_word_t *result, + const uECC_word_t *input, + const uECC_word_t *mod, + wordcount_t num_words) { + uECC_word_t a[uECC_MAX_WORDS], b[uECC_MAX_WORDS], u[uECC_MAX_WORDS], v[uECC_MAX_WORDS]; + cmpresult_t cmpResult; + + if (uECC_vli_isZero(input, num_words)) { + uECC_vli_clear(result, num_words); + return; + } + + uECC_vli_set(a, input, num_words); + uECC_vli_set(b, mod, num_words); + uECC_vli_clear(u, num_words); + u[0] = 1; + uECC_vli_clear(v, num_words); + while ((cmpResult = uECC_vli_cmp_unsafe(a, b, num_words)) != 0) { + if (EVEN(a)) { + uECC_vli_rshift1(a, num_words); + vli_modInv_update(u, mod, num_words); + } else if (EVEN(b)) { + uECC_vli_rshift1(b, num_words); + vli_modInv_update(v, mod, num_words); + } else if (cmpResult > 0) { + uECC_vli_sub(a, a, b, num_words); + uECC_vli_rshift1(a, num_words); + if (uECC_vli_cmp_unsafe(u, v, num_words) < 0) { + uECC_vli_add(u, u, mod, num_words); + } + uECC_vli_sub(u, u, v, num_words); + vli_modInv_update(u, mod, num_words); + } else { + uECC_vli_sub(b, b, a, num_words); + uECC_vli_rshift1(b, num_words); + if (uECC_vli_cmp_unsafe(v, u, num_words) < 0) { + uECC_vli_add(v, v, mod, num_words); + } + uECC_vli_sub(v, v, u, num_words); + vli_modInv_update(v, mod, num_words); + } + } + uECC_vli_set(result, u, num_words); +} + +/* ------ Point operations ------ */ + +//#include "curve-specific.inc" +#include "curve-specific.h" + +/* Returns 1 if 'point' is the point at infinity, 0 otherwise. */ +#define EccPoint_isZero(point, curve) uECC_vli_isZero((point), (curve)->num_words * 2) + +/* Point multiplication algorithm using Montgomery's ladder with co-Z coordinates. +From http://eprint.iacr.org/2011/338.pdf +*/ + +/* Modify (x1, y1) => (x1 * z^2, y1 * z^3) */ +static void apply_z(uECC_word_t * X1, + uECC_word_t * Y1, + const uECC_word_t * const Z, + uECC_Curve curve) { + uECC_word_t t1[uECC_MAX_WORDS]; + + uECC_vli_modSquare_fast(t1, Z, curve); /* z^2 */ + uECC_vli_modMult_fast(X1, X1, t1, curve); /* x1 * z^2 */ + uECC_vli_modMult_fast(t1, t1, Z, curve); /* z^3 */ + uECC_vli_modMult_fast(Y1, Y1, t1, curve); /* y1 * z^3 */ +} + +/* P = (x1, y1) => 2P, (x2, y2) => P' */ +static void XYcZ_initial_double(uECC_word_t * X1, + uECC_word_t * Y1, + uECC_word_t * X2, + uECC_word_t * Y2, + const uECC_word_t * const initial_Z, + uECC_Curve curve) { + uECC_word_t z[uECC_MAX_WORDS]; + wordcount_t num_words = curve->num_words; + if (initial_Z) { + uECC_vli_set(z, initial_Z, num_words); + } else { + uECC_vli_clear(z, num_words); + z[0] = 1; + } + + uECC_vli_set(X2, X1, num_words); + uECC_vli_set(Y2, Y1, num_words); + + apply_z(X1, Y1, z, curve); + curve->double_jacobian(X1, Y1, z, curve); + apply_z(X2, Y2, z, curve); +} + +/* Input P = (x1, y1, Z), Q = (x2, y2, Z) + Output P' = (x1', y1', Z3), P + Q = (x3, y3, Z3) + or P => P', Q => P + Q +*/ +static void XYcZ_add(uECC_word_t * X1, + uECC_word_t * Y1, + uECC_word_t * X2, + uECC_word_t * Y2, + uECC_Curve curve) { + /* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */ + uECC_word_t t5[uECC_MAX_WORDS]; + wordcount_t num_words = curve->num_words; + + uECC_vli_modSub(t5, X2, X1, curve->p, num_words); /* t5 = x2 - x1 */ + uECC_vli_modSquare_fast(t5, t5, curve); /* t5 = (x2 - x1)^2 = A */ + uECC_vli_modMult_fast(X1, X1, t5, curve); /* t1 = x1*A = B */ + uECC_vli_modMult_fast(X2, X2, t5, curve); /* t3 = x2*A = C */ + uECC_vli_modSub(Y2, Y2, Y1, curve->p, num_words); /* t4 = y2 - y1 */ + uECC_vli_modSquare_fast(t5, Y2, curve); /* t5 = (y2 - y1)^2 = D */ + + uECC_vli_modSub(t5, t5, X1, curve->p, num_words); /* t5 = D - B */ + uECC_vli_modSub(t5, t5, X2, curve->p, num_words); /* t5 = D - B - C = x3 */ + uECC_vli_modSub(X2, X2, X1, curve->p, num_words); /* t3 = C - B */ + uECC_vli_modMult_fast(Y1, Y1, X2, curve); /* t2 = y1*(C - B) */ + uECC_vli_modSub(X2, X1, t5, curve->p, num_words); /* t3 = B - x3 */ + uECC_vli_modMult_fast(Y2, Y2, X2, curve); /* t4 = (y2 - y1)*(B - x3) */ + uECC_vli_modSub(Y2, Y2, Y1, curve->p, num_words); /* t4 = y3 */ + + uECC_vli_set(X2, t5, num_words); +} + +/* Input P = (x1, y1, Z), Q = (x2, y2, Z) + Output P + Q = (x3, y3, Z3), P - Q = (x3', y3', Z3) + or P => P - Q, Q => P + Q +*/ +static void XYcZ_addC(uECC_word_t * X1, + uECC_word_t * Y1, + uECC_word_t * X2, + uECC_word_t * Y2, + uECC_Curve curve) { + /* t1 = X1, t2 = Y1, t3 = X2, t4 = Y2 */ + uECC_word_t t5[uECC_MAX_WORDS]; + uECC_word_t t6[uECC_MAX_WORDS]; + uECC_word_t t7[uECC_MAX_WORDS]; + wordcount_t num_words = curve->num_words; + + uECC_vli_modSub(t5, X2, X1, curve->p, num_words); /* t5 = x2 - x1 */ + uECC_vli_modSquare_fast(t5, t5, curve); /* t5 = (x2 - x1)^2 = A */ + uECC_vli_modMult_fast(X1, X1, t5, curve); /* t1 = x1*A = B */ + uECC_vli_modMult_fast(X2, X2, t5, curve); /* t3 = x2*A = C */ + uECC_vli_modAdd(t5, Y2, Y1, curve->p, num_words); /* t5 = y2 + y1 */ + uECC_vli_modSub(Y2, Y2, Y1, curve->p, num_words); /* t4 = y2 - y1 */ + + uECC_vli_modSub(t6, X2, X1, curve->p, num_words); /* t6 = C - B */ + uECC_vli_modMult_fast(Y1, Y1, t6, curve); /* t2 = y1 * (C - B) = E */ + uECC_vli_modAdd(t6, X1, X2, curve->p, num_words); /* t6 = B + C */ + uECC_vli_modSquare_fast(X2, Y2, curve); /* t3 = (y2 - y1)^2 = D */ + uECC_vli_modSub(X2, X2, t6, curve->p, num_words); /* t3 = D - (B + C) = x3 */ + + uECC_vli_modSub(t7, X1, X2, curve->p, num_words); /* t7 = B - x3 */ + uECC_vli_modMult_fast(Y2, Y2, t7, curve); /* t4 = (y2 - y1)*(B - x3) */ + uECC_vli_modSub(Y2, Y2, Y1, curve->p, num_words); /* t4 = (y2 - y1)*(B - x3) - E = y3 */ + + uECC_vli_modSquare_fast(t7, t5, curve); /* t7 = (y2 + y1)^2 = F */ + uECC_vli_modSub(t7, t7, t6, curve->p, num_words); /* t7 = F - (B + C) = x3' */ + uECC_vli_modSub(t6, t7, X1, curve->p, num_words); /* t6 = x3' - B */ + uECC_vli_modMult_fast(t6, t6, t5, curve); /* t6 = (y2+y1)*(x3' - B) */ + uECC_vli_modSub(Y1, t6, Y1, curve->p, num_words); /* t2 = (y2+y1)*(x3' - B) - E = y3' */ + + uECC_vli_set(X1, t7, num_words); +} + +/* result may overlap point. */ +static void EccPoint_mult(uECC_word_t * result, + const uECC_word_t * point, + const uECC_word_t * scalar, + const uECC_word_t * initial_Z, + bitcount_t num_bits, + uECC_Curve curve) { + /* R0 and R1 */ + uECC_word_t Rx[2][uECC_MAX_WORDS]; + uECC_word_t Ry[2][uECC_MAX_WORDS]; + uECC_word_t z[uECC_MAX_WORDS]; + bitcount_t i; + uECC_word_t nb; + wordcount_t num_words = curve->num_words; + + uECC_vli_set(Rx[1], point, num_words); + uECC_vli_set(Ry[1], point + num_words, num_words); + + XYcZ_initial_double(Rx[1], Ry[1], Rx[0], Ry[0], initial_Z, curve); + + for (i = num_bits - 2; i > 0; --i) { + nb = !uECC_vli_testBit(scalar, i); + XYcZ_addC(Rx[1 - nb], Ry[1 - nb], Rx[nb], Ry[nb], curve); + XYcZ_add(Rx[nb], Ry[nb], Rx[1 - nb], Ry[1 - nb], curve); + } + + nb = !uECC_vli_testBit(scalar, 0); + XYcZ_addC(Rx[1 - nb], Ry[1 - nb], Rx[nb], Ry[nb], curve); + + /* Find final 1/Z value. */ + uECC_vli_modSub(z, Rx[1], Rx[0], curve->p, num_words); /* X1 - X0 */ + uECC_vli_modMult_fast(z, z, Ry[1 - nb], curve); /* Yb * (X1 - X0) */ + uECC_vli_modMult_fast(z, z, point, curve); /* xP * Yb * (X1 - X0) */ + uECC_vli_modInv(z, z, curve->p, num_words); /* 1 / (xP * Yb * (X1 - X0)) */ + /* yP / (xP * Yb * (X1 - X0)) */ + uECC_vli_modMult_fast(z, z, point + num_words, curve); + uECC_vli_modMult_fast(z, z, Rx[1 - nb], curve); /* Xb * yP / (xP * Yb * (X1 - X0)) */ + /* End 1/Z calculation */ + + XYcZ_add(Rx[nb], Ry[nb], Rx[1 - nb], Ry[1 - nb], curve); + apply_z(Rx[0], Ry[0], z, curve); + + uECC_vli_set(result, Rx[0], num_words); + uECC_vli_set(result + num_words, Ry[0], num_words); +} + +static uECC_word_t regularize_k(const uECC_word_t * const k, + uECC_word_t *k0, + uECC_word_t *k1, + uECC_Curve curve) { + wordcount_t num_n_words = BITS_TO_WORDS(curve->num_n_bits); + bitcount_t num_n_bits = curve->num_n_bits; + uECC_word_t carry = uECC_vli_add(k0, k, curve->n, num_n_words) || + (num_n_bits < ((bitcount_t)num_n_words * uECC_WORD_SIZE * 8) && + uECC_vli_testBit(k0, num_n_bits)); + uECC_vli_add(k1, k0, curve->n, num_n_words); + return carry; +} + +static uECC_word_t EccPoint_compute_public_key(uECC_word_t *result, + uECC_word_t *private_key, + uECC_Curve curve) { + uECC_word_t tmp1[uECC_MAX_WORDS]; + uECC_word_t tmp2[uECC_MAX_WORDS]; + uECC_word_t *p2[2] = {tmp1, tmp2}; + uECC_word_t carry; + + /* Regularize the bitcount for the private key so that attackers cannot use a side channel + attack to learn the number of leading zeros. */ + carry = regularize_k(private_key, tmp1, tmp2, curve); + + EccPoint_mult(result, curve->G, p2[!carry], 0, curve->num_n_bits + 1, curve); + + if (EccPoint_isZero(result, curve)) { + return 0; + } + return 1; +} + +#if uECC_WORD_SIZE == 1 + +uECC_VLI_API void uECC_vli_nativeToBytes(uint8_t *bytes, + int num_bytes, + const uint8_t *native) { + wordcount_t i; + for (i = 0; i < num_bytes; ++i) { + bytes[i] = native[(num_bytes - 1) - i]; + } +} + +uECC_VLI_API void uECC_vli_bytesToNative(uint8_t *native, + const uint8_t *bytes, + int num_bytes) { + uECC_vli_nativeToBytes(native, num_bytes, bytes); +} + +#else + +uECC_VLI_API void uECC_vli_nativeToBytes(uint8_t *bytes, + int num_bytes, + const uECC_word_t *native) { + wordcount_t i; + for (i = 0; i < num_bytes; ++i) { + unsigned b = num_bytes - 1 - i; + bytes[i] = native[b / uECC_WORD_SIZE] >> (8 * (b % uECC_WORD_SIZE)); + } +} + +uECC_VLI_API void uECC_vli_bytesToNative(uECC_word_t *native, + const uint8_t *bytes, + int num_bytes) { + wordcount_t i; + uECC_vli_clear(native, (num_bytes + (uECC_WORD_SIZE - 1)) / uECC_WORD_SIZE); + for (i = 0; i < num_bytes; ++i) { + unsigned b = num_bytes - 1 - i; + native[b / uECC_WORD_SIZE] |= + (uECC_word_t)bytes[i] << (8 * (b % uECC_WORD_SIZE)); + } +} + +#endif /* uECC_WORD_SIZE */ + +/* Generates a random integer in the range 0 < random < top. + Both random and top have num_words words. */ +uECC_VLI_API int uECC_generate_random_int(uECC_word_t *random, + const uECC_word_t *top, + wordcount_t num_words) { + uECC_word_t mask = (uECC_word_t)-1; + uECC_word_t tries; + bitcount_t num_bits = uECC_vli_numBits(top, num_words); + + if (!g_rng_function) { + return 0; + } + + for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) { + if (!g_rng_function((uint8_t *)random, num_words * uECC_WORD_SIZE)) { + return 0; + } + random[num_words - 1] &= mask >> ((bitcount_t)(num_words * uECC_WORD_SIZE * 8 - num_bits)); + if (!uECC_vli_isZero(random, num_words) && + uECC_vli_cmp(top, random, num_words) == 1) { + return 1; + } + } + return 0; +} + +int uECC_make_key(uint8_t *public_key, + uint8_t *private_key, + uECC_Curve curve) { +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + uECC_word_t *_private = (uECC_word_t *)private_key; + uECC_word_t *_public = (uECC_word_t *)public_key; +#else + uECC_word_t _private[uECC_MAX_WORDS]; + uECC_word_t _public[uECC_MAX_WORDS * 2]; +#endif + uECC_word_t tries; + + for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) { + if (!uECC_generate_random_int(_private, curve->n, BITS_TO_WORDS(curve->num_n_bits))) { + return 0; + } + + if (EccPoint_compute_public_key(_public, _private, curve)) { +#if uECC_VLI_NATIVE_LITTLE_ENDIAN == 0 + uECC_vli_nativeToBytes(private_key, BITS_TO_BYTES(curve->num_n_bits), _private); + uECC_vli_nativeToBytes(public_key, curve->num_bytes, _public); + uECC_vli_nativeToBytes( + public_key + curve->num_bytes, curve->num_bytes, _public + curve->num_words); +#endif + return 1; + } + } + return 0; +} + +int uECC_shared_secret(const uint8_t *public_key, + const uint8_t *private_key, + uint8_t *secret, + uECC_Curve curve) { + uECC_word_t _public[uECC_MAX_WORDS * 2]; + uECC_word_t _private[uECC_MAX_WORDS]; + + uECC_word_t tmp[uECC_MAX_WORDS]; + uECC_word_t *p2[2] = {_private, tmp}; + uECC_word_t *initial_Z = 0; + uECC_word_t carry; + wordcount_t num_words = curve->num_words; + wordcount_t num_bytes = curve->num_bytes; + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy((uint8_t *) _private, private_key, num_bytes); + bcopy((uint8_t *) _public, public_key, num_bytes*2); +#else + uECC_vli_bytesToNative(_private, private_key, BITS_TO_BYTES(curve->num_n_bits)); + uECC_vli_bytesToNative(_public, public_key, num_bytes); + uECC_vli_bytesToNative(_public + num_words, public_key + num_bytes, num_bytes); +#endif + + /* Regularize the bitcount for the private key so that attackers cannot use a side channel + attack to learn the number of leading zeros. */ + carry = regularize_k(_private, _private, tmp, curve); + + /* If an RNG function was specified, try to get a random initial Z value to improve + protection against side-channel attacks. */ + if (g_rng_function) { + if (!uECC_generate_random_int(p2[carry], curve->p, num_words)) { + return 0; + } + initial_Z = p2[carry]; + } + + EccPoint_mult(_public, _public, p2[!carry], initial_Z, curve->num_n_bits + 1, curve); +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy((uint8_t *) secret, (uint8_t *) _public, num_bytes); +#else + uECC_vli_nativeToBytes(secret, num_bytes, _public); +#endif + return !EccPoint_isZero(_public, curve); +} + +#if uECC_SUPPORT_COMPRESSED_POINT +void uECC_compress(const uint8_t *public_key, uint8_t *compressed, uECC_Curve curve) { + wordcount_t i; + for (i = 0; i < curve->num_bytes; ++i) { + compressed[i+1] = public_key[i]; + } +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + compressed[0] = 2 + (public_key[curve->num_bytes] & 0x01); +#else + compressed[0] = 2 + (public_key[curve->num_bytes * 2 - 1] & 0x01); +#endif +} + +void uECC_decompress(const uint8_t *compressed, uint8_t *public_key, uECC_Curve curve) { +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + uECC_word_t *point = (uECC_word_t *)public_key; +#else + uECC_word_t point[uECC_MAX_WORDS * 2]; +#endif + uECC_word_t *y = point + curve->num_words; +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy(public_key, compressed+1, curve->num_bytes); +#else + uECC_vli_bytesToNative(point, compressed + 1, curve->num_bytes); +#endif + curve->x_side(y, point, curve); + curve->mod_sqrt(y, curve); + + if ((y[0] & 0x01) != (compressed[0] & 0x01)) { + uECC_vli_sub(y, curve->p, y, curve->num_words); + } + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN == 0 + uECC_vli_nativeToBytes(public_key, curve->num_bytes, point); + uECC_vli_nativeToBytes(public_key + curve->num_bytes, curve->num_bytes, y); +#endif +} +#endif /* uECC_SUPPORT_COMPRESSED_POINT */ + +int uECC_valid_point(const uECC_word_t *point, uECC_Curve curve) { + uECC_word_t tmp1[uECC_MAX_WORDS]; + uECC_word_t tmp2[uECC_MAX_WORDS]; + wordcount_t num_words = curve->num_words; + + /* The point at infinity is invalid. */ + if (EccPoint_isZero(point, curve)) { + return 0; + } + + /* x and y must be smaller than p. */ + if (uECC_vli_cmp_unsafe(curve->p, point, num_words) != 1 || + uECC_vli_cmp_unsafe(curve->p, point + num_words, num_words) != 1) { + return 0; + } + + uECC_vli_modSquare_fast(tmp1, point + num_words, curve); + curve->x_side(tmp2, point, curve); /* tmp2 = x^3 + ax + b */ + + /* Make sure that y^2 == x^3 + ax + b */ + return (int)(uECC_vli_equal(tmp1, tmp2, num_words)); +} + +int uECC_valid_public_key(const uint8_t *public_key, uECC_Curve curve) { +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + uECC_word_t *_public = (uECC_word_t *)public_key; +#else + uECC_word_t _public[uECC_MAX_WORDS * 2]; +#endif + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN == 0 + uECC_vli_bytesToNative(_public, public_key, curve->num_bytes); + uECC_vli_bytesToNative( + _public + curve->num_words, public_key + curve->num_bytes, curve->num_bytes); +#endif + return uECC_valid_point(_public, curve); +} + +int uECC_compute_public_key(const uint8_t *private_key, uint8_t *public_key, uECC_Curve curve) { +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + uECC_word_t *_private = (uECC_word_t *)private_key; + uECC_word_t *_public = (uECC_word_t *)public_key; +#else + uECC_word_t _private[uECC_MAX_WORDS]; + uECC_word_t _public[uECC_MAX_WORDS * 2]; +#endif + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN == 0 + uECC_vli_bytesToNative(_private, private_key, BITS_TO_BYTES(curve->num_n_bits)); +#endif + + /* Make sure the private key is in the range [1, n-1]. */ + if (uECC_vli_isZero(_private, BITS_TO_WORDS(curve->num_n_bits))) { + return 0; + } + + if (uECC_vli_cmp(curve->n, _private, BITS_TO_WORDS(curve->num_n_bits)) != 1) { + return 0; + } + + /* Compute public key. */ + if (!EccPoint_compute_public_key(_public, _private, curve)) { + return 0; + } + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN == 0 + uECC_vli_nativeToBytes(public_key, curve->num_bytes, _public); + uECC_vli_nativeToBytes( + public_key + curve->num_bytes, curve->num_bytes, _public + curve->num_words); +#endif + return 1; +} + + +/* -------- ECDSA code -------- */ + +static void bits2int(uECC_word_t *native, + const uint8_t *bits, + unsigned bits_size, + uECC_Curve curve) { + unsigned num_n_bytes = BITS_TO_BYTES(curve->num_n_bits); + unsigned num_n_words = BITS_TO_WORDS(curve->num_n_bits); + int shift; + uECC_word_t carry; + uECC_word_t *ptr; + + if (bits_size > num_n_bytes) { + bits_size = num_n_bytes; + } + + uECC_vli_clear(native, num_n_words); +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy((uint8_t *) native, bits, bits_size); +#else + uECC_vli_bytesToNative(native, bits, bits_size); +#endif + if (bits_size * 8 <= (unsigned)curve->num_n_bits) { + return; + } + shift = bits_size * 8 - curve->num_n_bits; + carry = 0; + ptr = native + num_n_words; + while (ptr-- > native) { + uECC_word_t temp = *ptr; + *ptr = (temp >> shift) | carry; + carry = temp << (uECC_WORD_BITS - shift); + } + + /* Reduce mod curve_n */ + if (uECC_vli_cmp_unsafe(curve->n, native, num_n_words) != 1) { + uECC_vli_sub(native, native, curve->n, num_n_words); + } +} + +static int uECC_sign_with_k(const uint8_t *private_key, + const uint8_t *message_hash, + unsigned hash_size, + uECC_word_t *k, + uint8_t *signature, + uECC_Curve curve) { + + uECC_word_t tmp[uECC_MAX_WORDS]; + uECC_word_t s[uECC_MAX_WORDS]; + uECC_word_t *k2[2] = {tmp, s}; +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + uECC_word_t *p = (uECC_word_t *)signature; +#else + uECC_word_t p[uECC_MAX_WORDS * 2]; +#endif + uECC_word_t carry; + wordcount_t num_words = curve->num_words; + wordcount_t num_n_words = BITS_TO_WORDS(curve->num_n_bits); + bitcount_t num_n_bits = curve->num_n_bits; + + /* Make sure 0 < k < curve_n */ + if (uECC_vli_isZero(k, num_words) || uECC_vli_cmp(curve->n, k, num_n_words) != 1) { + return 0; + } + + carry = regularize_k(k, tmp, s, curve); + EccPoint_mult(p, curve->G, k2[!carry], 0, num_n_bits + 1, curve); + if (uECC_vli_isZero(p, num_words)) { + return 0; + } + + /* If an RNG function was specified, get a random number + to prevent side channel analysis of k. */ + if (!g_rng_function) { + uECC_vli_clear(tmp, num_n_words); + tmp[0] = 1; + } else if (!uECC_generate_random_int(tmp, curve->n, num_n_words)) { + return 0; + } + + /* Prevent side channel analysis of uECC_vli_modInv() to determine + bits of k / the private key by premultiplying by a random number */ + uECC_vli_modMult(k, k, tmp, curve->n, num_n_words); /* k' = rand * k */ + uECC_vli_modInv(k, k, curve->n, num_n_words); /* k = 1 / k' */ + uECC_vli_modMult(k, k, tmp, curve->n, num_n_words); /* k = 1 / k */ + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN == 0 + uECC_vli_nativeToBytes(signature, curve->num_bytes, p); /* store r */ +#endif + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy((uint8_t *) tmp, private_key, BITS_TO_BYTES(curve->num_n_bits)); +#else + uECC_vli_bytesToNative(tmp, private_key, BITS_TO_BYTES(curve->num_n_bits)); /* tmp = d */ +#endif + + s[num_n_words - 1] = 0; + uECC_vli_set(s, p, num_words); + uECC_vli_modMult(s, tmp, s, curve->n, num_n_words); /* s = r*d */ + + bits2int(tmp, message_hash, hash_size, curve); + uECC_vli_modAdd(s, tmp, s, curve->n, num_n_words); /* s = e + r*d */ + uECC_vli_modMult(s, s, k, curve->n, num_n_words); /* s = (e + r*d) / k */ + if (uECC_vli_numBits(s, num_n_words) > (bitcount_t)curve->num_bytes * 8) { + return 0; + } +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy((uint8_t *) signature + curve->num_bytes, (uint8_t *) s, curve->num_bytes); +#else + uECC_vli_nativeToBytes(signature + curve->num_bytes, curve->num_bytes, s); +#endif + return 1; +} + +int uECC_sign(const uint8_t *private_key, + const uint8_t *message_hash, + unsigned hash_size, + uint8_t *signature, + uECC_Curve curve) { + uECC_word_t k[uECC_MAX_WORDS]; + uECC_word_t tries; + + for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) { + if (!uECC_generate_random_int(k, curve->n, BITS_TO_WORDS(curve->num_n_bits))) { + return 0; + } + + if (uECC_sign_with_k(private_key, message_hash, hash_size, k, signature, curve)) { + return 1; + } + } + return 0; +} + +/* Compute an HMAC using K as a key (as in RFC 6979). Note that K is always + the same size as the hash result size. */ +static void HMAC_init(const uECC_HashContext *hash_context, const uint8_t *K) { + uint8_t *pad = hash_context->tmp + 2 * hash_context->result_size; + unsigned i; + for (i = 0; i < hash_context->result_size; ++i) + pad[i] = K[i] ^ 0x36; + for (; i < hash_context->block_size; ++i) + pad[i] = 0x36; + + hash_context->init_hash(hash_context); + hash_context->update_hash(hash_context, pad, hash_context->block_size); +} + +static void HMAC_update(const uECC_HashContext *hash_context, + const uint8_t *message, + unsigned message_size) { + hash_context->update_hash(hash_context, message, message_size); +} + +static void HMAC_finish(const uECC_HashContext *hash_context, + const uint8_t *K, + uint8_t *result) { + uint8_t *pad = hash_context->tmp + 2 * hash_context->result_size; + unsigned i; + for (i = 0; i < hash_context->result_size; ++i) + pad[i] = K[i] ^ 0x5c; + for (; i < hash_context->block_size; ++i) + pad[i] = 0x5c; + + hash_context->finish_hash(hash_context, result); + + hash_context->init_hash(hash_context); + hash_context->update_hash(hash_context, pad, hash_context->block_size); + hash_context->update_hash(hash_context, result, hash_context->result_size); + hash_context->finish_hash(hash_context, result); +} + +/* V = HMAC_K(V) */ +static void update_V(const uECC_HashContext *hash_context, uint8_t *K, uint8_t *V) { + HMAC_init(hash_context, K); + HMAC_update(hash_context, V, hash_context->result_size); + HMAC_finish(hash_context, K, V); +} + +/* Deterministic signing, similar to RFC 6979. Differences are: + * We just use H(m) directly rather than bits2octets(H(m)) + (it is not reduced modulo curve_n). + * We generate a value for k (aka T) directly rather than converting endianness. + + Layout of hash_context->tmp: <K> | <V> | (1 byte overlapped 0x00 or 0x01) / <HMAC pad> */ +int uECC_sign_deterministic(const uint8_t *private_key, + const uint8_t *message_hash, + unsigned hash_size, + const uECC_HashContext *hash_context, + uint8_t *signature, + uECC_Curve curve) { + uint8_t *K = hash_context->tmp; + uint8_t *V = K + hash_context->result_size; + wordcount_t num_bytes = curve->num_bytes; + wordcount_t num_n_words = BITS_TO_WORDS(curve->num_n_bits); + bitcount_t num_n_bits = curve->num_n_bits; + uECC_word_t tries; + unsigned i; + for (i = 0; i < hash_context->result_size; ++i) { + V[i] = 0x01; + K[i] = 0; + } + + /* K = HMAC_K(V || 0x00 || int2octets(x) || h(m)) */ + HMAC_init(hash_context, K); + V[hash_context->result_size] = 0x00; + HMAC_update(hash_context, V, hash_context->result_size + 1); + HMAC_update(hash_context, private_key, num_bytes); + HMAC_update(hash_context, message_hash, hash_size); + HMAC_finish(hash_context, K, K); + + update_V(hash_context, K, V); + + /* K = HMAC_K(V || 0x01 || int2octets(x) || h(m)) */ + HMAC_init(hash_context, K); + V[hash_context->result_size] = 0x01; + HMAC_update(hash_context, V, hash_context->result_size + 1); + HMAC_update(hash_context, private_key, num_bytes); + HMAC_update(hash_context, message_hash, hash_size); + HMAC_finish(hash_context, K, K); + + update_V(hash_context, K, V); + + for (tries = 0; tries < uECC_RNG_MAX_TRIES; ++tries) { + uECC_word_t T[uECC_MAX_WORDS]; + uint8_t *T_ptr = (uint8_t *)T; + wordcount_t T_bytes = 0; + for (;;) { + update_V(hash_context, K, V); + for (i = 0; i < hash_context->result_size; ++i) { + T_ptr[T_bytes++] = V[i]; + if (T_bytes >= num_n_words * uECC_WORD_SIZE) { + goto filled; + } + } + } + filled: + if ((bitcount_t)num_n_words * uECC_WORD_SIZE * 8 > num_n_bits) { + uECC_word_t mask = (uECC_word_t)-1; + T[num_n_words - 1] &= + mask >> ((bitcount_t)(num_n_words * uECC_WORD_SIZE * 8 - num_n_bits)); + } + + if (uECC_sign_with_k(private_key, message_hash, hash_size, T, signature, curve)) { + return 1; + } + + /* K = HMAC_K(V || 0x00) */ + HMAC_init(hash_context, K); + V[hash_context->result_size] = 0x00; + HMAC_update(hash_context, V, hash_context->result_size + 1); + HMAC_finish(hash_context, K, K); + + update_V(hash_context, K, V); + } + return 0; +} + +static bitcount_t smax(bitcount_t a, bitcount_t b) { + return (a > b ? a : b); +} + +int uECC_verify(const uint8_t *public_key, + const uint8_t *message_hash, + unsigned hash_size, + const uint8_t *signature, + uECC_Curve curve) { + uECC_word_t u1[uECC_MAX_WORDS], u2[uECC_MAX_WORDS]; + uECC_word_t z[uECC_MAX_WORDS]; + uECC_word_t sum[uECC_MAX_WORDS * 2]; + uECC_word_t rx[uECC_MAX_WORDS]; + uECC_word_t ry[uECC_MAX_WORDS]; + uECC_word_t tx[uECC_MAX_WORDS]; + uECC_word_t ty[uECC_MAX_WORDS]; + uECC_word_t tz[uECC_MAX_WORDS]; + const uECC_word_t *points[4]; + const uECC_word_t *point; + bitcount_t num_bits; + bitcount_t i; +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + uECC_word_t *_public = (uECC_word_t *)public_key; +#else + uECC_word_t _public[uECC_MAX_WORDS * 2]; +#endif + uECC_word_t r[uECC_MAX_WORDS], s[uECC_MAX_WORDS]; + wordcount_t num_words = curve->num_words; + wordcount_t num_n_words = BITS_TO_WORDS(curve->num_n_bits); + + rx[num_n_words - 1] = 0; + r[num_n_words - 1] = 0; + s[num_n_words - 1] = 0; + +#if uECC_VLI_NATIVE_LITTLE_ENDIAN + bcopy((uint8_t *) r, signature, curve->num_bytes); + bcopy((uint8_t *) s, signature + curve->num_bytes, curve->num_bytes); +#else + uECC_vli_bytesToNative(_public, public_key, curve->num_bytes); + uECC_vli_bytesToNative( + _public + num_words, public_key + curve->num_bytes, curve->num_bytes); + uECC_vli_bytesToNative(r, signature, curve->num_bytes); + uECC_vli_bytesToNative(s, signature + curve->num_bytes, curve->num_bytes); +#endif + + /* r, s must not be 0. */ + if (uECC_vli_isZero(r, num_words) || uECC_vli_isZero(s, num_words)) { + return 0; + } + + /* r, s must be < n. */ + if (uECC_vli_cmp_unsafe(curve->n, r, num_n_words) != 1 || + uECC_vli_cmp_unsafe(curve->n, s, num_n_words) != 1) { + return 0; + } + + /* Calculate u1 and u2. */ + uECC_vli_modInv(z, s, curve->n, num_n_words); /* z = 1/s */ + u1[num_n_words - 1] = 0; + bits2int(u1, message_hash, hash_size, curve); + uECC_vli_modMult(u1, u1, z, curve->n, num_n_words); /* u1 = e/s */ + uECC_vli_modMult(u2, r, z, curve->n, num_n_words); /* u2 = r/s */ + + /* Calculate sum = G + Q. */ + uECC_vli_set(sum, _public, num_words); + uECC_vli_set(sum + num_words, _public + num_words, num_words); + uECC_vli_set(tx, curve->G, num_words); + uECC_vli_set(ty, curve->G + num_words, num_words); + uECC_vli_modSub(z, sum, tx, curve->p, num_words); /* z = x2 - x1 */ + XYcZ_add(tx, ty, sum, sum + num_words, curve); + uECC_vli_modInv(z, z, curve->p, num_words); /* z = 1/z */ + apply_z(sum, sum + num_words, z, curve); + + /* Use Shamir's trick to calculate u1*G + u2*Q */ + points[0] = 0; + points[1] = curve->G; + points[2] = _public; + points[3] = sum; + num_bits = smax(uECC_vli_numBits(u1, num_n_words), + uECC_vli_numBits(u2, num_n_words)); + + point = points[(!!uECC_vli_testBit(u1, num_bits - 1)) | + ((!!uECC_vli_testBit(u2, num_bits - 1)) << 1)]; + uECC_vli_set(rx, point, num_words); + uECC_vli_set(ry, point + num_words, num_words); + uECC_vli_clear(z, num_words); + z[0] = 1; + + for (i = num_bits - 2; i >= 0; --i) { + uECC_word_t index; + curve->double_jacobian(rx, ry, z, curve); + + index = (!!uECC_vli_testBit(u1, i)) | ((!!uECC_vli_testBit(u2, i)) << 1); + point = points[index]; + if (point) { + uECC_vli_set(tx, point, num_words); + uECC_vli_set(ty, point + num_words, num_words); + apply_z(tx, ty, z, curve); + uECC_vli_modSub(tz, rx, tx, curve->p, num_words); /* Z = x2 - x1 */ + XYcZ_add(tx, ty, rx, ry, curve); + uECC_vli_modMult_fast(z, z, tz, curve); + } + } + + uECC_vli_modInv(z, z, curve->p, num_words); /* Z = 1/Z */ + apply_z(rx, ry, z, curve); + + /* v = x1 (mod n) */ + if (uECC_vli_cmp_unsafe(curve->n, rx, num_n_words) != 1) { + uECC_vli_sub(rx, rx, curve->n, num_n_words); + } + + /* Accept only if v == r. */ + return (int)(uECC_vli_equal(rx, r, num_words)); +} + +#if uECC_ENABLE_VLI_API + +unsigned uECC_curve_num_words(uECC_Curve curve) { + return curve->num_words; +} + +unsigned uECC_curve_num_bytes(uECC_Curve curve) { + return curve->num_bytes; +} + +unsigned uECC_curve_num_bits(uECC_Curve curve) { + return curve->num_bytes * 8; +} + +unsigned uECC_curve_num_n_words(uECC_Curve curve) { + return BITS_TO_WORDS(curve->num_n_bits); +} + +unsigned uECC_curve_num_n_bytes(uECC_Curve curve) { + return BITS_TO_BYTES(curve->num_n_bits); +} + +unsigned uECC_curve_num_n_bits(uECC_Curve curve) { + return curve->num_n_bits; +} + +const uECC_word_t *uECC_curve_p(uECC_Curve curve) { + return curve->p; +} + +const uECC_word_t *uECC_curve_n(uECC_Curve curve) { + return curve->n; +} + +const uECC_word_t *uECC_curve_G(uECC_Curve curve) { + return curve->G; +} + +const uECC_word_t *uECC_curve_b(uECC_Curve curve) { + return curve->b; +} + +#if uECC_SUPPORT_COMPRESSED_POINT +void uECC_vli_mod_sqrt(uECC_word_t *a, uECC_Curve curve) { + curve->mod_sqrt(a, curve); +} +#endif + +void uECC_vli_mmod_fast(uECC_word_t *result, uECC_word_t *product, uECC_Curve curve) { +#if (uECC_OPTIMIZATION_LEVEL > 0) + curve->mmod_fast(result, product); +#else + uECC_vli_mmod(result, product, curve->p, curve->num_words); +#endif +} + +void uECC_point_mult(uECC_word_t *result, + const uECC_word_t *point, + const uECC_word_t *scalar, + uECC_Curve curve) { + uECC_word_t tmp1[uECC_MAX_WORDS]; + uECC_word_t tmp2[uECC_MAX_WORDS]; + uECC_word_t *p2[2] = {tmp1, tmp2}; + uECC_word_t carry = regularize_k(scalar, tmp1, tmp2, curve); + + EccPoint_mult(result, point, p2[!carry], 0, curve->num_n_bits + 1, curve); +} + +#endif /* uECC_ENABLE_VLI_API */