--- /dev/null
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdbool.h>
+#include <assert.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include <stdlib.h>
+
+#include "shamirssecret.h"
+
+#define MAX_LENGTH 1024
+#define ERROREXIT(str...) {fprintf(stderr, str); exit(1);}
+
+#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;
+ 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));
+}
+
+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) {
+ 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;
+}
+
+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) {
+ 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 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;
+ while((i = getopt(argc, argv, "scn:k:f:o:i:h?")) != -1)
+ switch(i) {
+ case 's':
+ if ((split & 0x2) && !(split & 0x1))
+ ERROREXIT("-s (split) and -c (combine) are mutually exclusive\n")
+ else
+ split = (0x2 | 0x1);
+ break;
+ case 'c':
+ if ((split & 0x2) && (split & 0x1))
+ ERROREXIT("-s (split) and -c (combine) are mutually exclusive\n")
+ else
+ split = 0x2;
+ break;
+ case 'n': {
+ int t = atoi(optarg);
+ if (t <= 0 || t >= P)
+ ERROREXIT("n must be > 0 and < %u\n", P)
+ else
+ total_shares = t;
+ break;
+ }
+ case 'k': {
+ int t = atoi(optarg);
+ if (t <= 0 || t >= P)
+ ERROREXIT("n must be > 0 and < %u\n", P)
+ else
+ shares_required = t;
+ break;
+ }
+ case 'i':
+ in_file = optarg;
+ break;
+ case 'o':
+ out_file_param = optarg;
+ break;
+ case 'f':
+ if (files_count >= P-1)
+ ERROREXIT("May only specify up to %u files\n", P-1)
+ files[files_count++] = optarg;
+ break;
+ case 'h':
+ case '?':
+ printf("Split usage: -s -n <total shares> -k <shares required> -i <input file> -o <output file path base>\n");
+ printf("Combine usage: -c -k <shares provided == shares required> <-f <share>>*k -o <output file>\n");
+ exit(0);
+ break;
+ default:
+ ERROREXIT("getopt failed?\n")
+ }
+ if (!(split & 0x2))
+ ERROREXIT("Must specify one of -c, -s or -?\n")
+ split &= 0x1;
+
+ if (argc != optind)
+ ERROREXIT("Invalid argument\n")
+
+ if (split) {
+ if (!total_shares || !shares_required)
+ ERROREXIT("n and k must be set.\n")
+
+ if (shares_required > total_shares)
+ ERROREXIT("k must be <= n\n")
+
+ if (files_count != 0 || !in_file || !out_file_param)
+ ERROREXIT("Must specify -i <input file> and -o <output file path base> but not -f in split mode.\n")
+
+ FILE* random = fopen("/dev/random", "r");
+ assert(random);
+ FILE* secret_file = fopen(in_file, "r");
+ if (!secret_file)
+ ERROREXIT("Could not open %s for reading.\n", in_file)
+
+ uint8_t secret[MAX_LENGTH];
+
+ size_t secret_length = fread(secret, 1, MAX_LENGTH*sizeof(uint8_t), secret_file);
+ if (secret_length == 0)
+ ERROREXIT("Error reading secret\n")
+ if (fread(secret, 1, 1, secret_file) > 0)
+ ERROREXIT("Secret may not be longer than %u\n", MAX_LENGTH)
+ fclose(secret_file);
+ printf("Using secret of length %lu\n", secret_length);
+
+ uint8_t a[shares_required], D[total_shares][secret_length];
+
+ 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);
+
+ // 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);
+
+ 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 < 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)
+ ERROREXIT("Could not write 1 byte to %s\n", out_file_name_buf)
+
+ if (fwrite(D[i], 1, secret_length, out_file) != secret_length)
+ ERROREXIT("Could not write %lu bytes to %s\n", secret_length, out_file_name_buf)
+
+ 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(in_file, 0, strlen(in_file));
+
+ fclose(random);
+ } else {
+ if (!shares_required)
+ ERROREXIT("k must be set.\n")
+
+ if (files_count != shares_required || in_file || !out_file_param)
+ ERROREXIT("Must not specify -i and must specify -o and exactly k -f <input file>s in combine mode.\n")
+
+ uint8_t x[shares_required], q[shares_required];
+ FILE* files_fps[shares_required];
+
+ 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])
+ if (fread(&x[i], sizeof(uint8_t), 1, files_fps[i]) != 1)
+ ERROREXIT("Couldn't read the x byte of %s\n", files[i])
+ }
+
+ uint8_t secret[MAX_LENGTH];
+
+ uint32_t i = 0;
+ while (fread(&q[0], sizeof(uint8_t), 1, files_fps[0]) == 1) {
+ 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, shares_required);
+ }
+ printf("Got secret of length %u\n", i);
+
+ FILE* out_file = fopen(out_file_param, "w+");
+ fwrite(secret, sizeof(uint8_t), i, out_file);
+ fclose(out_file);
+
+ 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)
-#define _GNU_SOURCE
-
#include <stdint.h>
-#include <stdio.h>
#include <assert.h>
-#include <string.h>
-#include <unistd.h>
-#include <stdlib.h>
-#include <sys/mman.h>
-#include <stdbool.h>
-#define MAX_LENGTH 1024
-#define ERROREXIT(str...) {fprintf(stderr, str); exit(1);}
+#include "shamirssecret.h"
/*
* Calculations across the finite field GF(2^8)
*/
-#define P 256
#ifndef TEST
static uint8_t field_add(uint8_t a, uint8_t b) {
* Calculations across the polynomial q
*/
#ifndef TEST
-static uint8_t calculateQ(uint8_t a[], uint8_t k, uint8_t x) {
+/**
+ * Calculates the Y coordinate that the point with the given X
+ * coefficients[0] == secret, the rest are random values
+ */
+uint8_t calculateQ(uint8_t coefficients[], uint8_t shares_required, uint8_t x) {
assert(x != 0); // q(0) == secret, though so does a[0]
- uint8_t ret = a[0];
- for (uint8_t i = 1; i < k; i++) {
- ret = field_add(ret, field_mul(a[i], field_pow(x, i)));
+ uint8_t ret = coefficients[0];
+ for (uint8_t i = 1; i < shares_required; i++) {
+ ret = field_add(ret, field_mul(coefficients[i], field_pow(x, i)));
}
return ret;
}
-uint8_t calculateSecret(uint8_t x[], uint8_t q[], uint8_t k) {
+/**
+ * Derives the secret given a set of shares_required points (x and q coordinates)
+ */
+uint8_t calculateSecret(uint8_t x[], uint8_t q[], uint8_t shares_required) {
// Calculate the x^0 term using a derivation of the forumula at
// http://en.wikipedia.org/wiki/Lagrange_polynomial#Example_2
uint8_t ret = 0;
- for (uint8_t i = 0; i < k; i++) {
+ for (uint8_t i = 0; i < shares_required; i++) {
uint8_t temp = q[i];
- for (uint8_t j = 0; j < k; j++) {
+ for (uint8_t j = 0; j < shares_required; j++) {
if (i == j)
continue;
temp = field_mul(temp, field_neg(x[j]));
}
return ret;
}
-
-
-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 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;
- while((i = getopt(argc, argv, "scn:k:f:o:i:h?")) != -1)
- switch(i) {
- case 's':
- if ((split & 0x2) && !(split & 0x1))
- ERROREXIT("-s (split) and -c (combine) are mutually exclusive\n")
- else
- split = (0x2 | 0x1);
- break;
- case 'c':
- if ((split & 0x2) && (split & 0x1))
- ERROREXIT("-s (split) and -c (combine) are mutually exclusive\n")
- else
- split = 0x2;
- break;
- case 'n': {
- int t = atoi(optarg);
- if (t <= 0 || t >= P)
- ERROREXIT("n must be > 0 and < %u\n", P)
- else
- total_shares = t;
- break;
- }
- case 'k': {
- int t = atoi(optarg);
- if (t <= 0 || t >= P)
- ERROREXIT("n must be > 0 and < %u\n", P)
- else
- shares_required = t;
- break;
- }
- case 'i':
- in_file = optarg;
- break;
- case 'o':
- out_file_param = optarg;
- break;
- case 'f':
- if (files_count >= P-1)
- ERROREXIT("May only specify up to %u files\n", P-1)
- files[files_count++] = optarg;
- break;
- case 'h':
- case '?':
- printf("Split usage: -s -n <total shares> -k <shares required> -i <input file> -o <output file path base>\n");
- printf("Combine usage: -c -k <shares provided == shares required> <-f <share>>*k -o <output file>\n");
- exit(0);
- break;
- default:
- ERROREXIT("getopt failed?\n")
- }
- if (!(split & 0x2))
- ERROREXIT("Must specify one of -c, -s or -?\n")
- split &= 0x1;
-
- if (argc != optind)
- ERROREXIT("Invalid argument\n")
-
- if (split) {
- if (!total_shares || !shares_required)
- ERROREXIT("n and k must be set.\n")
-
- if (shares_required > total_shares)
- ERROREXIT("k must be <= n\n")
-
- if (files_count != 0 || !in_file || !out_file_param)
- ERROREXIT("Must specify -i <input file> and -o <output file path base> but not -f in split mode.\n")
-
- FILE* random = fopen("/dev/random", "r");
- assert(random);
- FILE* secret_file = fopen(in_file, "r");
- if (!secret_file)
- ERROREXIT("Could not open %s for reading.\n", in_file)
-
- uint8_t secret[MAX_LENGTH];
-
- size_t secret_length = fread(secret, 1, MAX_LENGTH*sizeof(uint8_t), secret_file);
- if (secret_length == 0)
- ERROREXIT("Error reading secret\n")
- if (fread(secret, 1, 1, secret_file) > 0)
- ERROREXIT("Secret may not be longer than %u\n", MAX_LENGTH)
- fclose(secret_file);
- printf("Using secret of length %lu\n", secret_length);
-
- uint8_t a[shares_required], D[total_shares][secret_length];
-
- 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);
-
- // 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 < 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)
- ERROREXIT("Could not write 1 byte to %s\n", out_file_name_buf)
-
- if (fwrite(D[i], 1, secret_length, out_file) != secret_length)
- ERROREXIT("Could not write %lu bytes to %s\n", secret_length, out_file_name_buf)
-
- 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(in_file, 0, strlen(in_file));
-
- fclose(random);
- } else {
- if (!shares_required)
- ERROREXIT("k must be set.\n")
-
- if (files_count != shares_required || in_file || !out_file_param)
- ERROREXIT("Must not specify -i and must specify -o and exactly k -f <input file>s in combine mode.\n")
-
- uint8_t x[shares_required], q[shares_required];
- FILE* files_fps[shares_required];
-
- 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])
- if (fread(&x[i], sizeof(uint8_t), 1, files_fps[i]) != 1)
- ERROREXIT("Couldn't read the x byte of %s\n", files[i])
- }
-
- uint8_t secret[MAX_LENGTH];
-
- uint32_t i = 0;
- while (fread(&q[0], sizeof(uint8_t), 1, files_fps[0]) == 1) {
- 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, shares_required);
- }
- printf("Got secret of length %u\n", i);
-
- FILE* out_file = fopen(out_file_param, "w+");
- fwrite(secret, sizeof(uint8_t), i, out_file);
- fclose(out_file);
-
- 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)