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Solve challenge 6

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This commit is contained in:
Dimitri Lozeve 2020-06-10 18:07:26 +02:00
parent 87a1547478
commit cb30d47479
4 changed files with 14 additions and 19 deletions
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24
src/ex06/main.c
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@ -6,23 +6,15 @@
#define BUF_SIZE 4096 #define BUF_SIZE 4096
double normalized_edit_distance(unsigned int keysize, double normalized_edit_distance(
const unsigned char buf[static keysize * 4], unsigned int keysize, unsigned int blocks_count,
unsigned int blocks_count) { const unsigned char buf[static keysize * blocks_count]) {
char blocks[blocks_count][keysize];
for (size_t i = 0; i < blocks_count; ++i) {
for (size_t j = 0; j < keysize; ++j) {
blocks[i][j] = buf[i * keysize + j];
}
}
double avg_dist = 0; double avg_dist = 0;
for (size_t i = 0; i < blocks_count - 1; ++i) { for (size_t i = 0; i < blocks_count - 1; ++i) {
avg_dist += hamming(keysize, blocks[i], blocks[i + 1]) / (double)keysize; avg_dist += hamming(keysize, &buf[i * keysize], &buf[(i + 1) * keysize]);
} }
return avg_dist / ((double)blocks_count - 1.0); return avg_dist / (double)keysize / ((double)blocks_count - 1.0);
} }
int main(int argc, char *argv[]) { int main(int argc, char *argv[]) {
@ -66,10 +58,10 @@ int main(int argc, char *argv[]) {
return EXIT_FAILURE; return EXIT_FAILURE;
} }
unsigned int keysize = 40; unsigned int keysize = 0;
double min_edit_dist = INFINITY; double min_edit_dist = INFINITY;
for (unsigned int i = 40; i > 1; --i) { for (unsigned int i = 2; i < 40; ++i) {
double edit_dist = normalized_edit_distance(i, buf, len / i); double edit_dist = normalized_edit_distance(i, len / i, buf);
if (edit_dist < min_edit_dist) { if (edit_dist < min_edit_dist) {
min_edit_dist = edit_dist; min_edit_dist = edit_dist;
keysize = i; keysize = i;

3
src/utils.c
View file

@ -115,7 +115,8 @@ double frequency_score(size_t len, const char buf[static len]) {
return chi2; return chi2;
} }
unsigned int hamming(size_t len, const char s1[static len], const char s2[static len]) { unsigned int hamming(size_t len, const unsigned char s1[static len],
const unsigned char s2[static len]) {
unsigned int res = 0; unsigned int res = 0;
for (size_t i = 0; i < len; ++i) { for (size_t i = 0; i < len; ++i) {
unsigned int n = s1[i] ^ s2[i]; unsigned int n = s1[i] ^ s2[i];

2
src/utils.h
View file

@ -8,7 +8,7 @@ size_t hex_to_bytes(unsigned char out[static 1], const char hex[static 1]);
char *bytes_to_base64(char out[static 4], const unsigned char in[static 3], size_t len); char *bytes_to_base64(char out[static 4], const unsigned char in[static 3], size_t len);
size_t base64_to_bytes(unsigned char out[static 3], const char in[static 4]); size_t base64_to_bytes(unsigned char out[static 3], const char in[static 4]);
double frequency_score(size_t len, const char buf[static len]); double frequency_score(size_t len, const char buf[static len]);
unsigned int hamming(size_t len, const char s1[static len], const char s2[static len]); unsigned int hamming(size_t len, const unsigned char s1[static len], const unsigned char s2[static len]);
char best_single_char_xor_key(size_t len, unsigned char buf[static len]); char best_single_char_xor_key(size_t len, unsigned char buf[static len]);
#endif /* UTILS_H */ #endif /* UTILS_H */

4
tests/main.c
View file

@ -83,7 +83,9 @@ static MunitResult test_hamming(const MunitParameter params[], void *data) {
(void)params; (void)params;
(void)data; (void)data;
assert_int(hamming(14, "this is a test", "wokka wokka!!!"), ==, 37); assert_int(hamming(14, (const unsigned char *)"this is a test",
(const unsigned char *)"wokka wokka!!!"),
==, 37);
return MUNIT_OK; return MUNIT_OK;
} }