From: Matt Corallo Date: Fri, 13 Dec 2013 03:33:21 +0000 (-0500) Subject: Use random X coordinates X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=085515e769d794f70c3f9ae0c80902dd5a5eee09;p=shamirs Use random X coordinates --- diff --git a/main.c b/main.c index af352fd..42ec45e 100644 --- a/main.c +++ b/main.c @@ -32,16 +32,20 @@ #define MAX_LENGTH 1024 #define ERROREXIT(str...) {fprintf(stderr, str); exit(1);} +#ifndef RAND_SOURCE +#define RAND_SOURCE "/dev/random" +#endif + #ifndef TEST -static 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; +static void derive_missing_part(uint8_t total_shares, uint8_t shares_required, bool parts_have[], const uint8_t* split_version, const uint8_t* split_x, uint8_t split_index, uint8_t split_size) { + const uint8_t (*D)[split_size] = (const 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; + x[x_pos] = split_x[i]; q[x_pos++] = D[i][split_index]; } } @@ -78,23 +82,23 @@ static void derive_missing_part(uint8_t total_shares, uint8_t shares_required, b memset(q, 0, sizeof(q)); } -static 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) { +static 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, const uint8_t* split_version, const uint8_t* x, 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); + return derive_missing_part(total_shares, shares_required, parts_have, split_version, x, 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); + check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, parts_included, progress+1, split_version, x, 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); + check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, parts_included+1, progress+1, split_version, x, split_index, split_size); parts_have[progress] = 0; } -static 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) { +static void check_possible_missing_part_derivations(uint8_t total_shares, uint8_t shares_required, const uint8_t* split_version, const uint8_t* x, 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); + check_possible_missing_part_derivations_intern(total_shares, shares_required, parts_have, 0, 0, split_version, x, split_index, split_size); } @@ -174,7 +178,7 @@ int main(int argc, char* argv[]) { if (files_count != 0 || !in_file || !out_file_param) ERROREXIT("Must specify -i and -o but not -f in split mode.\n") - FILE* random = fopen("/dev/random", "r"); + FILE* random = fopen(RAND_SOURCE, "r"); assert(random); FILE* secret_file = fopen(in_file, "r"); if (!secret_file) @@ -190,38 +194,46 @@ int main(int argc, char* argv[]) { fclose(secret_file); printf("Using secret of length %lu\n", secret_length); - uint8_t a[shares_required], D[total_shares][secret_length]; - + uint8_t a[shares_required], x[total_shares], D[total_shares][secret_length]; + + // TODO: The following loop may take a long time and eat lots of /dev/random if total_shares is high + for (uint32_t i = 0; i < total_shares; i++) { + int32_t j = 0; + do { + assert(fread(&x[i], sizeof(uint8_t), 1, random) == 1); + if (x[i] == 0) + continue; + for (j = 0; j < i; j++) + if (x[j] == x[i]) + break; + } while (j < i); // Inner loop will get to j = i when x[j] != x[i] for all j + if (i % 32 == 31) + printf("Finished picking X coordinates for %u shares\n", i+1); + } for (uint32_t i = 0; i < secret_length; i++) { a[0] = secret[i]; 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); + D[j][i] = calculateQ(a, shares_required, x[j]); // Now, for paranoia'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); + check_possible_missing_part_derivations(total_shares, shares_required, &(D[0][0]), x, i, secret_length); - if (i % 32 == 0 && i != 0) - printf("Finished processing %u bytes.\n", i); + if (i % 32 == 31) + printf("Finished processing %u bytes.\n", i+1); } char out_file_name_buf[strlen(out_file_param) + 4]; strcpy(out_file_name_buf, out_file_param); 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]); - printf("\n");*/ - sprintf(((char*)out_file_name_buf) + strlen(out_file_param), "%u", i); FILE* out_file = fopen(out_file_name_buf, "w+"); if (!out_file) ERROREXIT("Could not open output file %s\n", out_file_name_buf) - uint8_t x = i+1; - if (fwrite(&x, sizeof(uint8_t), 1, out_file) != 1) + if (fwrite(&x[i], sizeof(uint8_t), 1, out_file) != 1) ERROREXIT("Could not write 1 byte to %s\n", out_file_name_buf) if (fwrite(D[i], 1, secret_length, out_file) != secret_length) @@ -229,14 +241,11 @@ int main(int argc, char* argv[]) { fclose(out_file); } - /*printf("secret = "); - for (uint8_t i = 0; i < secret_length; i++) - 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(x, 0, sizeof(uint8_t)*total_shares); memset(in_file, 0, strlen(in_file)); fclose(random);