X-Git-Url: http://git.bitcoin.ninja/index.cgi?p=shamirs;a=blobdiff_plain;f=shamirssecret.c;h=92c2c9cf8bdf1fac83be393a7175ee1f923fbc2a;hp=893d9787f88a5cdd558e0557027f6ffffc08c74a;hb=39318502b0e2fedca71d901ba007fea2a0d26208;hpb=df22cea18150ab0d21f1ebe4304a4de8d64d808e diff --git a/shamirssecret.c b/shamirssecret.c index 893d978..92c2c9c 100644 --- a/shamirssecret.c +++ b/shamirssecret.c @@ -7,72 +7,115 @@ #include #include #include +#include #define MAX_LENGTH 1024 +#define ERROREXIT(str...) {fprintf(stderr, str); exit(1);} /* - * Calculations across the finite field GF(p) - * Lots of side-channel attacks in here + * Calculations across the finite field GF(2^8) */ -/* -const uint8_t p = 251; // Largest 8-bit prime +#define P 256 + +#ifndef TEST static uint8_t field_add(uint8_t a, uint8_t b) { - assert(a < p && b < p); - return (((uint16_t)a) + ((uint16_t)b)) % p; + return a ^ b; } static uint8_t field_sub(uint8_t a, uint8_t b) { - assert(a < p && b < p); - return (((uint16_t)p) + ((uint16_t)a) - ((uint16_t)b)) % p; + return a ^ b; } -static uint8_t field_mul(uint8_t a, uint8_t b) { - assert(a < p && b < p); - return (((uint16_t)a) * ((uint16_t)b)) % p; +static uint8_t field_neg(uint8_t a) { + return field_sub(0, a); } - -static uint8_t field_pow(uint8_t a, uint8_t e) { - assert(a < p); - uint8_t ret = 1; - for (uint8_t i = 0; i < e; i++) { - ret = field_mul(ret, a); - } +#endif + +static const uint8_t exp[P] = { + 0x01, 0x03, 0x05, 0x0f, 0x11, 0x33, 0x55, 0xff, 0x1a, 0x2e, 0x72, 0x96, 0xa1, 0xf8, 0x13, 0x35, + 0x5f, 0xe1, 0x38, 0x48, 0xd8, 0x73, 0x95, 0xa4, 0xf7, 0x02, 0x06, 0x0a, 0x1e, 0x22, 0x66, 0xaa, + 0xe5, 0x34, 0x5c, 0xe4, 0x37, 0x59, 0xeb, 0x26, 0x6a, 0xbe, 0xd9, 0x70, 0x90, 0xab, 0xe6, 0x31, + 0x53, 0xf5, 0x04, 0x0c, 0x14, 0x3c, 0x44, 0xcc, 0x4f, 0xd1, 0x68, 0xb8, 0xd3, 0x6e, 0xb2, 0xcd, + 0x4c, 0xd4, 0x67, 0xa9, 0xe0, 0x3b, 0x4d, 0xd7, 0x62, 0xa6, 0xf1, 0x08, 0x18, 0x28, 0x78, 0x88, + 0x83, 0x9e, 0xb9, 0xd0, 0x6b, 0xbd, 0xdc, 0x7f, 0x81, 0x98, 0xb3, 0xce, 0x49, 0xdb, 0x76, 0x9a, + 0xb5, 0xc4, 0x57, 0xf9, 0x10, 0x30, 0x50, 0xf0, 0x0b, 0x1d, 0x27, 0x69, 0xbb, 0xd6, 0x61, 0xa3, + 0xfe, 0x19, 0x2b, 0x7d, 0x87, 0x92, 0xad, 0xec, 0x2f, 0x71, 0x93, 0xae, 0xe9, 0x20, 0x60, 0xa0, + 0xfb, 0x16, 0x3a, 0x4e, 0xd2, 0x6d, 0xb7, 0xc2, 0x5d, 0xe7, 0x32, 0x56, 0xfa, 0x15, 0x3f, 0x41, + 0xc3, 0x5e, 0xe2, 0x3d, 0x47, 0xc9, 0x40, 0xc0, 0x5b, 0xed, 0x2c, 0x74, 0x9c, 0xbf, 0xda, 0x75, + 0x9f, 0xba, 0xd5, 0x64, 0xac, 0xef, 0x2a, 0x7e, 0x82, 0x9d, 0xbc, 0xdf, 0x7a, 0x8e, 0x89, 0x80, + 0x9b, 0xb6, 0xc1, 0x58, 0xe8, 0x23, 0x65, 0xaf, 0xea, 0x25, 0x6f, 0xb1, 0xc8, 0x43, 0xc5, 0x54, + 0xfc, 0x1f, 0x21, 0x63, 0xa5, 0xf4, 0x07, 0x09, 0x1b, 0x2d, 0x77, 0x99, 0xb0, 0xcb, 0x46, 0xca, + 0x45, 0xcf, 0x4a, 0xde, 0x79, 0x8b, 0x86, 0x91, 0xa8, 0xe3, 0x3e, 0x42, 0xc6, 0x51, 0xf3, 0x0e, + 0x12, 0x36, 0x5a, 0xee, 0x29, 0x7b, 0x8d, 0x8c, 0x8f, 0x8a, 0x85, 0x94, 0xa7, 0xf2, 0x0d, 0x17, + 0x39, 0x4b, 0xdd, 0x7c, 0x84, 0x97, 0xa2, 0xfd, 0x1c, 0x24, 0x6c, 0xb4, 0xc7, 0x52, 0xf6, 0x01}; +static const uint8_t log[P] = { + 0x00, // log(0) is not defined + 0xff, 0x19, 0x01, 0x32, 0x02, 0x1a, 0xc6, 0x4b, 0xc7, 0x1b, 0x68, 0x33, 0xee, 0xdf, 0x03, 0x64, + 0x04, 0xe0, 0x0e, 0x34, 0x8d, 0x81, 0xef, 0x4c, 0x71, 0x08, 0xc8, 0xf8, 0x69, 0x1c, 0xc1, 0x7d, + 0xc2, 0x1d, 0xb5, 0xf9, 0xb9, 0x27, 0x6a, 0x4d, 0xe4, 0xa6, 0x72, 0x9a, 0xc9, 0x09, 0x78, 0x65, + 0x2f, 0x8a, 0x05, 0x21, 0x0f, 0xe1, 0x24, 0x12, 0xf0, 0x82, 0x45, 0x35, 0x93, 0xda, 0x8e, 0x96, + 0x8f, 0xdb, 0xbd, 0x36, 0xd0, 0xce, 0x94, 0x13, 0x5c, 0xd2, 0xf1, 0x40, 0x46, 0x83, 0x38, 0x66, + 0xdd, 0xfd, 0x30, 0xbf, 0x06, 0x8b, 0x62, 0xb3, 0x25, 0xe2, 0x98, 0x22, 0x88, 0x91, 0x10, 0x7e, + 0x6e, 0x48, 0xc3, 0xa3, 0xb6, 0x1e, 0x42, 0x3a, 0x6b, 0x28, 0x54, 0xfa, 0x85, 0x3d, 0xba, 0x2b, + 0x79, 0x0a, 0x15, 0x9b, 0x9f, 0x5e, 0xca, 0x4e, 0xd4, 0xac, 0xe5, 0xf3, 0x73, 0xa7, 0x57, 0xaf, + 0x58, 0xa8, 0x50, 0xf4, 0xea, 0xd6, 0x74, 0x4f, 0xae, 0xe9, 0xd5, 0xe7, 0xe6, 0xad, 0xe8, 0x2c, + 0xd7, 0x75, 0x7a, 0xeb, 0x16, 0x0b, 0xf5, 0x59, 0xcb, 0x5f, 0xb0, 0x9c, 0xa9, 0x51, 0xa0, 0x7f, + 0x0c, 0xf6, 0x6f, 0x17, 0xc4, 0x49, 0xec, 0xd8, 0x43, 0x1f, 0x2d, 0xa4, 0x76, 0x7b, 0xb7, 0xcc, + 0xbb, 0x3e, 0x5a, 0xfb, 0x60, 0xb1, 0x86, 0x3b, 0x52, 0xa1, 0x6c, 0xaa, 0x55, 0x29, 0x9d, 0x97, + 0xb2, 0x87, 0x90, 0x61, 0xbe, 0xdc, 0xfc, 0xbc, 0x95, 0xcf, 0xcd, 0x37, 0x3f, 0x5b, 0xd1, 0x53, + 0x39, 0x84, 0x3c, 0x41, 0xa2, 0x6d, 0x47, 0x14, 0x2a, 0x9e, 0x5d, 0x56, 0xf2, 0xd3, 0xab, 0x44, + 0x11, 0x92, 0xd9, 0x23, 0x20, 0x2e, 0x89, 0xb4, 0x7c, 0xb8, 0x26, 0x77, 0x99, 0xe3, 0xa5, 0x67, + 0x4a, 0xed, 0xde, 0xc5, 0x31, 0xfe, 0x18, 0x0d, 0x63, 0x8c, 0x80, 0xc0, 0xf7, 0x70, 0x07}; + +// We disable lots of optimizations that result in non-constant runtime (+/- branch delays) +static uint8_t field_mul_ret(uint8_t calc, uint8_t a, uint8_t b) __attribute__((optimize("-O0"))) __attribute__((noinline)); +static uint8_t field_mul_ret(uint8_t calc, uint8_t a, uint8_t b) { + uint8_t ret, ret2; + if (a == 0) + ret2 = 0; + else + ret2 = calc; + if (b == 0) + ret = 0; + else + ret = ret2; return ret; } - -static uint8_t field_neg(uint8_t a) { - assert(a < p); - if (a == 0) - return 0; - return p - a; +static uint8_t field_mul(uint8_t a, uint8_t b) { + return field_mul_ret(exp[(log[a] + log[b]) % 255], a, b); } static uint8_t field_invert(uint8_t a) { - // Brute force, yay! - assert(a < p); - for (uint8_t i = 0; i < p; i++) { - if (field_mul(i, a) == 1) - return i; - } - assert(0); -}*/ - - - -/* - * Calculations across the finite field GF(2^8) - */ -const uint16_t p = 256; -static uint8_t field_add(uint8_t a, uint8_t b) { - return a ^ b; + assert(a != 0); + return exp[0xff - log[a]]; // log[1] == 0xff } -static uint8_t field_sub(uint8_t a, uint8_t b) { - return a ^ b; +// We disable lots of optimizations that result in non-constant runtime (+/- branch delays) +static uint8_t field_pow_ret(uint8_t calc, uint8_t a, uint8_t e) __attribute__((optimize("-O0"))) __attribute__((noinline)); +static uint8_t field_pow_ret(uint8_t calc, uint8_t a, uint8_t e) { + uint8_t ret, ret2; + if (a == 0) + ret2 = 0; + else + ret2 = calc; + if (e == 0) + ret = 1; + else + ret = ret2; + return ret; +} +static uint8_t field_pow(uint8_t a, uint8_t e) { +#ifndef TEST + // Although this function works for a==0, its not trivially obvious why, + // and since we never call with a==0, we just assert a != 0 (except when testing) + assert(a != 0); +#endif + return field_pow_ret(exp[(log[a] * e) % 255], a, e); } -static uint8_t field_mul(uint8_t a, uint8_t b) { - // TODO side-channel attacks here? +#ifdef TEST +static uint8_t field_mul_calc(uint8_t a, uint8_t b) { + // side-channel attacks here uint8_t ret = 0; uint8_t counter; uint8_t carry; @@ -82,53 +125,42 @@ static uint8_t field_mul(uint8_t a, uint8_t b) { carry = (a & 0x80); a <<= 1; if (carry) - a ^= 0x1b; /* what x^8 is modulo x^8 + x^4 + x^3 + x + 1 */ + a ^= 0x1b; // what x^8 is modulo x^8 + x^4 + x^3 + x + 1 b >>= 1; } return ret; } - -// WARNING: Do not use if e is secret (potential side-channel attacks) -static uint8_t field_pow(uint8_t a, uint8_t e) { - // TODO: This could be sped up pretty trivially +static uint8_t field_pow_calc(uint8_t a, uint8_t e) { uint8_t ret = 1; for (uint8_t i = 0; i < e; i++) - ret = field_mul(ret, a); + ret = field_mul_calc(ret, a); return ret; } +int main() { + // Test inversion with the logarithm tables + for (uint16_t i = 1; i < P; i++) + assert(field_mul_calc(i, field_invert(i)) == 1); + + // Test multiplication with the logarithm tables + for (uint16_t i = 0; i < P; i++) { + for (uint16_t j = 0; j < P; j++) + assert(field_mul(i, j) == field_mul_calc(i, j)); + } -static uint8_t field_neg(uint8_t a) { - return field_sub(0, a); -} - -static const uint8_t inverse[] = { // Multiplicative inverse of each element in the field - 0xff, // 0 has no inverse - 0x01, 0x8d, 0xf6, 0xcb, 0x52, 0x7b, 0xd1, 0xe8, 0x4f, 0x29, 0xc0, 0xb0, 0xe1, 0xe5, 0xc7, 0x74, - 0xb4, 0xaa, 0x4b, 0x99, 0x2b, 0x60, 0x5f, 0x58, 0x3f, 0xfd, 0xcc, 0xff, 0x40, 0xee, 0xb2, 0x3a, - 0x6e, 0x5a, 0xf1, 0x55, 0x4d, 0xa8, 0xc9, 0xc1, 0x0a, 0x98, 0x15, 0x30, 0x44, 0xa2, 0xc2, 0x2c, - 0x45, 0x92, 0x6c, 0xf3, 0x39, 0x66, 0x42, 0xf2, 0x35, 0x20, 0x6f, 0x77, 0xbb, 0x59, 0x19, 0x1d, - 0xfe, 0x37, 0x67, 0x2d, 0x31, 0xf5, 0x69, 0xa7, 0x64, 0xab, 0x13, 0x54, 0x25, 0xe9, 0x09, 0xed, - 0x5c, 0x05, 0xca, 0x4c, 0x24, 0x87, 0xbf, 0x18, 0x3e, 0x22, 0xf0, 0x51, 0xec, 0x61, 0x17, 0x16, - 0x5e, 0xaf, 0xd3, 0x49, 0xa6, 0x36, 0x43, 0xf4, 0x47, 0x91, 0xdf, 0x33, 0x93, 0x21, 0x3b, 0x79, - 0xb7, 0x97, 0x85, 0x10, 0xb5, 0xba, 0x3c, 0xb6, 0x70, 0xd0, 0x06, 0xa1, 0xfa, 0x81, 0x82, 0x83, - 0x7e, 0x7f, 0x80, 0x96, 0x73, 0xbe, 0x56, 0x9b, 0x9e, 0x95, 0xd9, 0xf7, 0x02, 0xb9, 0xa4, 0xde, - 0x6a, 0x32, 0x6d, 0xd8, 0x8a, 0x84, 0x72, 0x2a, 0x14, 0x9f, 0x88, 0xf9, 0xdc, 0x89, 0x9a, 0xfb, - 0x7c, 0x2e, 0xc3, 0x8f, 0xb8, 0x65, 0x48, 0x26, 0xc8, 0x12, 0x4a, 0xce, 0xe7, 0xd2, 0x62, 0x0c, - 0xe0, 0x1f, 0xef, 0x11, 0x75, 0x78, 0x71, 0xa5, 0x8e, 0x76, 0x3d, 0xbd, 0xbc, 0x86, 0x57, 0x0b, - 0x28, 0x2f, 0xa3, 0xda, 0xd4, 0xe4, 0x0f, 0xa9, 0x27, 0x53, 0x04, 0x1b, 0xfc, 0xac, 0xe6, 0x7a, - 0x07, 0xae, 0x63, 0xc5, 0xdb, 0xe2, 0xea, 0x94, 0x8b, 0xc4, 0xd5, 0x9d, 0xf8, 0x90, 0x6b, 0xb1, - 0x0d, 0xd6, 0xeb, 0xc6, 0x0e, 0xcf, 0xad, 0x08, 0x4e, 0xd7, 0xe3, 0x5d, 0x50, 0x1e, 0xb3, 0x5b, - 0x23, 0x38, 0x34, 0x68, 0x46, 0x03, 0x8c, 0xdd, 0x9c, 0x7d, 0xa0, 0xcd, 0x1a, 0x41, 0x1c}; -static uint8_t field_invert(uint8_t a) { - assert(a != 0); - return inverse[a]; + // Test exponentiation with the logarithm tables + for (uint16_t i = 0; i < P; i++) { + for (uint16_t j = 0; j < P; j++) + assert(field_pow(i, j) == field_pow_calc(i, j)); + } } +#endif // defined(TEST) /* * Calculations across the polynomial q */ +#ifndef TEST static uint8_t calculateQ(uint8_t a[], uint8_t k, uint8_t x) { assert(x != 0); // q(0) == secret, though so does a[0] uint8_t ret = a[0]; @@ -155,14 +187,79 @@ uint8_t calculateSecret(uint8_t x[], uint8_t q[], uint8_t k) { return ret; } -#define ERROREXIT(str...) {fprintf(stderr, str); exit(1);} + +void derive_missing_part(uint8_t total_shares, uint8_t shares_required, bool parts_have[], uint8_t* split_version, uint8_t split_index, uint8_t split_size) { + uint8_t (*D)[split_size] = (uint8_t (*)[split_size])split_version; + uint8_t x[shares_required], q[shares_required]; + + // Fill in x/q with the selected shares + uint16_t x_pos = 0; + for (uint8_t i = 0; i < P-1; i++) { + if (parts_have[i]) { + x[x_pos] = i+1; + q[x_pos++] = D[i][split_index]; + } + } + assert(x_pos == shares_required - 1); + + // Now loop through ALL x we didn't already set (despite not having that many + // shares, because more shares could be added arbitrarily, any x should not be + // able to rule out any possible secrets) and try each possible q, making sure + // that each q gives us a new possibility for the secret. + bool impossible_secrets[P]; + memset(impossible_secrets, 0, sizeof(impossible_secrets)); + for (uint16_t final_x = 1; final_x < P; final_x++) { + bool x_already_used = false; + for (uint8_t j = 0; j < shares_required; j++) { + if (x[j] == final_x) + x_already_used = true; + } + if (x_already_used) + continue; + + x[shares_required-1] = final_x; + bool possible_secrets[P]; + memset(possible_secrets, 0, sizeof(possible_secrets)); + for (uint16_t new_q = 0; new_q < P; new_q++) { + q[shares_required-1] = new_q; + possible_secrets[calculateSecret(x, q, shares_required)] = 1; + } + + for (uint16_t i = 0; i < P; i++) + assert(possible_secrets[i]); + } + + //TODO: Check that gcc isn't optimizing this one away + memset(q, 0, sizeof(q)); +} + +void check_possible_missing_part_derivations_intern(uint8_t total_shares, uint8_t shares_required, bool parts_have[], uint8_t parts_included, uint16_t progress, uint8_t* split_version, uint8_t split_index, uint8_t split_size) { + if (parts_included == shares_required-1) + return derive_missing_part(total_shares, shares_required, parts_have, split_version, split_index, split_size); + + if (total_shares - progress < shares_required) + return; + + check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, parts_included, progress+1, split_version, split_index, split_size); + parts_have[progress] = 1; + check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, parts_included+1, progress+1, split_version, split_index, split_size); + parts_have[progress] = 0; +} + +void check_possible_missing_part_derivations(uint8_t total_shares, uint8_t shares_required, uint8_t* split_version, uint8_t split_index, uint8_t split_size) { + bool parts_have[P]; + memset(parts_have, 0, sizeof(parts_have)); + check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, 0, 0, split_version, split_index, split_size); +} + + int main(int argc, char* argv[]) { assert(mlockall(MCL_CURRENT | MCL_FUTURE) == 0); char split = 0; - uint8_t n = 0, k = 0; - char* files[p]; uint8_t files_count = 0; + uint8_t total_shares = 0, shares_required = 0; + char* files[P]; uint8_t files_count = 0; char *in_file = (void*)0, *out_file_param = (void*)0; int i; @@ -182,18 +279,18 @@ int main(int argc, char* argv[]) { break; case 'n': { int t = atoi(optarg); - if (t <= 0 || t >= p) - ERROREXIT("n must be > 0 and < %u\n", p) + if (t <= 0 || t >= P) + ERROREXIT("n must be > 0 and < %u\n", P) else - n = t; + total_shares = t; break; } case 'k': { int t = atoi(optarg); - if (t <= 0 || t >= p) - ERROREXIT("n must be > 0 and < %u\n", p) + if (t <= 0 || t >= P) + ERROREXIT("n must be > 0 and < %u\n", P) else - k = t; + shares_required = t; break; } case 'i': @@ -203,8 +300,8 @@ int main(int argc, char* argv[]) { out_file_param = optarg; break; case 'f': - if (files_count >= p-1) - ERROREXIT("May only specify up to %u files\n", p-1) + if (files_count >= P-1) + ERROREXIT("May only specify up to %u files\n", P-1) files[files_count++] = optarg; break; case 'h': @@ -217,17 +314,17 @@ int main(int argc, char* argv[]) { ERROREXIT("getopt failed?\n") } if (!(split & 0x2)) - ERROREXIT("Must specify either -c or -s\n") + ERROREXIT("Must specify one of -c, -s or -?\n") split &= 0x1; if (argc != optind) ERROREXIT("Invalid argument\n") if (split) { - if (!n || !k) + if (!total_shares || !shares_required) ERROREXIT("n and k must be set.\n") - if (k > n) + if (shares_required > total_shares) ERROREXIT("k must be <= n\n") if (files_count != 0 || !in_file || !out_file_param) @@ -240,7 +337,6 @@ int main(int argc, char* argv[]) { ERROREXIT("Could not open %s for reading.\n", in_file) uint8_t secret[MAX_LENGTH]; - memset(secret, 0, MAX_LENGTH*sizeof(uint8_t)); size_t secret_length = fread(secret, 1, MAX_LENGTH*sizeof(uint8_t), secret_file); if (secret_length == 0) @@ -250,23 +346,26 @@ int main(int argc, char* argv[]) { fclose(secret_file); printf("Using secret of length %lu\n", secret_length); - uint8_t a[secret_length][k], D[n][secret_length]; + uint8_t a[shares_required], D[total_shares][secret_length]; - for (uint8_t i = 0; i < secret_length; i++) { - a[i][0] = secret[i]; + for (uint32_t i = 0; i < secret_length; i++) { + a[0] = secret[i]; - for (uint8_t j = 1; j < k; j++) { - do - assert(fread(&a[i][j], sizeof(uint8_t), 1, random) == 1); - while (a[i][j] >= p); - } - for (uint8_t j = 0; j < n; j++) - D[j][i] = calculateQ(a[i], k, j+1); + for (uint8_t j = 1; j < shares_required; j++) + assert(fread(&a[j], sizeof(uint8_t), 1, random) == 1); + for (uint8_t j = 0; j < total_shares; j++) + D[j][i] = calculateQ(a, shares_required, j+1); + + // Now, for sanity's sake, we ensure that no matter which piece we are missing, we can derive no information about the secret + check_possible_missing_part_derivations(total_shares, shares_required, &(D[0][0]), i, secret_length); + + if (i % 32 == 0 && i != 0) + printf("Finished processing %u bytes.\n", i); } char out_file_name_buf[strlen(out_file_param) + 4]; strcpy(out_file_name_buf, out_file_param); - for (uint8_t i = 0; i < n; i++) { + for (uint8_t i = 0; i < total_shares; i++) { /*printf("%u-", i); for (uint8_t j = 0; j < secret_length; j++) printf("%02x", D[i][j]); @@ -291,18 +390,23 @@ int main(int argc, char* argv[]) { printf("%02x", secret[i]); printf("\n");*/ + // Clear sensitive data (No, GCC 4.7.2 is currently not optimizing this out) + memset(secret, 0, sizeof(uint8_t)*secret_length); + memset(a, 0, sizeof(uint8_t)*shares_required); + memset(in_file, 0, strlen(in_file)); + fclose(random); } else { - if (!k) + if (!shares_required) ERROREXIT("k must be set.\n") - if (files_count != k || in_file || !out_file_param) + if (files_count != shares_required || in_file || !out_file_param) ERROREXIT("Must not specify -i and must specify -o and exactly k -f s in combine mode.\n") - uint8_t x[k], q[k]; - FILE* files_fps[k]; + uint8_t x[shares_required], q[shares_required]; + FILE* files_fps[shares_required]; - for (uint8_t i = 0; i < k; i++) { + for (uint8_t i = 0; i < shares_required; i++) { files_fps[i] = fopen(files[i], "r"); if (!files_fps[i]) ERROREXIT("Couldn't open file %s for reading.\n", files[i]) @@ -312,13 +416,13 @@ int main(int argc, char* argv[]) { uint8_t secret[MAX_LENGTH]; - uint8_t i = 0; + uint32_t i = 0; while (fread(&q[0], sizeof(uint8_t), 1, files_fps[0]) == 1) { - for (uint8_t j = 1; j < k; j++) { + for (uint8_t j = 1; j < shares_required; j++) { if (fread(&q[j], sizeof(uint8_t), 1, files_fps[j]) != 1) ERROREXIT("Couldn't read next byte from %s\n", files[j]) } - secret[i++] = calculateSecret(x, q, k); + secret[i++] = calculateSecret(x, q, shares_required); } printf("Got secret of length %u\n", i); @@ -326,9 +430,18 @@ int main(int argc, char* argv[]) { fwrite(secret, sizeof(uint8_t), i, out_file); fclose(out_file); - for (uint8_t i = 0; i < k; i++) + for (uint8_t i = 0; i < shares_required; i++) fclose(files_fps[i]); + + // Clear sensitive data (No, GCC 4.7.2 is currently not optimizing this out) + memset(secret, 0, sizeof(uint8_t)*i); + memset(q, 0, sizeof(uint8_t)*shares_required); + memset(out_file_param, 0, strlen(out_file_param)); + for (uint8_t i = 0; i < shares_required; i++) + memset(files[i], 0, strlen(files[i])); + memset(x, 0, sizeof(uint8_t)*shares_required); } return 0; } +#endif // !defined(TEST)