#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);}
*/
#define P 256
+#ifndef TEST
static uint8_t field_add(uint8_t a, uint8_t b) {
return a ^ b;
}
static uint8_t field_neg(uint8_t a) {
return field_sub(0, a);
}
+#endif
static const uint8_t exp[P] = {
0x01, 0x03, 0x05, 0x0f, 0x11, 0x33, 0x55, 0xff, 0x1a, 0x2e, 0x72, 0x96, 0xa1, 0xf8, 0x13, 0x35,
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_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() {
assert(field_mul_calc(i, field_invert(i)) == 1);
// Test multiplication with the logarithm tables
- for (uint16_t i = 0; i < 2; i++) {
+ 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));
}
}
+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;
+ 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;
if (t <= 0 || t >= P)
ERROREXIT("n must be > 0 and < %u\n", P)
else
- n = t;
+ total_shares = t;
break;
}
case 'k': {
if (t <= 0 || t >= P)
ERROREXIT("n must be > 0 and < %u\n", P)
else
- k = t;
+ shares_required = t;
break;
}
case 'i':
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)
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)
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 (uint32_t i = 0; i < secret_length; i++) {
+ a[0] = secret[i];
- for (uint8_t i = 0; i < secret_length; i++) {
- a[i][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);
- for (uint8_t j = 1; j < k; j++)
- assert(fread(&a[i][j], sizeof(uint8_t), 1, random) == 1);
- for (uint8_t j = 0; j < n; j++)
- D[j][i] = calculateQ(a[i], k, 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]);
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 <input file>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])
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);
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;
projects / shamirs / blobdiff