diff options
| -rw-r--r-- | lib/lib.c | 27 | ||||
| -rw-r--r-- | lib/lib.h | 2 | ||||
| -rw-r--r-- | lib/lib2.c | 10 | ||||
| -rw-r--r-- | lib/lib2.h | 1 | ||||
| -rw-r--r-- | set1/task6.c | 28 | ||||
| -rw-r--r-- | set3/Makefile | 8 | ||||
| -rw-r--r-- | set3/task20.c | 64 |
7 files changed, 106 insertions, 34 deletions
@@ -555,4 +555,31 @@ int string_is_ecb_encrypted(char *string, int length_string, int blocksize) return (count_equal_blocks(string, length_string, blocksize) > (length_string/blocksize)); } +/** +* split ciphertext in blocks of size blocksize + * @return returns an array of string of size with blocksize elements + */ + + +char **transpose_blocks(char *ciphertext, int blocksize, int length) +{ + char **blocks; + int i, j; + int number_blocks = length / blocksize; + + blocks = malloc(blocksize*(sizeof(char*))); + + for(i=0;i<blocksize;i++) { + blocks[i] = malloc(number_blocks+1); + } + + for(j=0;j<blocksize;j++) { + for(i=0;i<number_blocks;i++) { + blocks[j][i] = ciphertext[(i*blocksize)+j]; + } + } + + return blocks; +} + @@ -24,6 +24,6 @@ char brute_force_single_byte_xor(char *string, int length, struct key_and_freq * int isprintable(char *string, int length); int read_base64_file(const char *file, char **out); int string_is_ecb_encrypted(char *string, int length_string, int blocksize); - +char **transpose_blocks(char *ciphertext, int blocksize, int length); #endif /* __CYRPTO_LIB__ */ @@ -6,12 +6,11 @@ * and append to last block so that it is also of blocksize length */ -char *pkcs7_padding(char *string, int length_string, int blocksize) +char *__pkcs7_padding(char *string, int length_string, int blocksize, int *padding) { char *result = NULL; int i; int value = blocksize - (length_string % blocksize); - result = malloc(length_string+value+1); memcpy(result, string, length_string); @@ -19,10 +18,15 @@ char *pkcs7_padding(char *string, int length_string, int blocksize) result[length_string+i] = (char) value; } result[length_string+i] = '\0'; - + *padding = value; return result; } +char *pkcs7_padding(char *string, int length_string, int blocksize) +{ + int not_interested; + return __pkcs7_padding(string, length_string, blocksize, ¬_interested); +} /** * unpadd a string * @param in string which should be unpadded @@ -15,6 +15,7 @@ char key[17]; char iv[17]; char *pkcs7_padding(char *string, int length_string, int blocksize); +char *__pkcs7_padding(char *string, int length_string, int blocksize, int *padding); int aes_cbc(char *in, int length_in, char *out, unsigned char *string_key, char *init_vector, int encrypt); int valid_pkcs7_padding(const char *in, int length_in, char *unpadded, int blocksize); int aes_ecb(char *in, int length_in, char *out, unsigned char *string_key, diff --git a/set1/task6.c b/set1/task6.c index 10e19b2..a6a4bfb 100644 --- a/set1/task6.c +++ b/set1/task6.c @@ -1,33 +1,5 @@ #include "../lib/lib.h" -/** - * split ciphertext in blocks of size blocksize - * @return returns an array of string of size with blocksize elements - */ - - -char **transpose_blocks(char *ciphertext, int blocksize, int length) -{ - char **blocks; - int i, j; - int number_blocks = length / blocksize; - - blocks = malloc(blocksize*(sizeof(char*))); - - for(i=0;i<blocksize;i++) { - blocks[i] = malloc(number_blocks+1); - } - - for(j=0;j<blocksize;j++) { - for(i=0;i<number_blocks;i++) { - blocks[j][i] = ciphertext[(i*blocksize)+j]; - } - } - - return blocks; -} - - int main() { int keysize; diff --git a/set3/Makefile b/set3/Makefile index d3b3f03..a6ed5fc 100644 --- a/set3/Makefile +++ b/set3/Makefile @@ -3,12 +3,16 @@ CC=gcc CFLAGS := -g $(CFLAGS) CLIBS=`pkg-config --cflags --libs libcrypto` -all: task17 task18 +all: task17 task18 task19 task20 task17: $(CC) $(CFLAGS) task17.c $(LIB) $(CLIBS) -o task17 task18: $(CC) $(CFLAGS) task18.c $(LIB) $(CLIBS) -o task18 +task19: + $(CC) $(CFLAGS) task19.c $(LIB) $(CLIBS) -o task19 +task20: + $(CC) $(CFLAGS) task20.c $(LIB) $(CLIBS) -o task20 clean: - rm task17 task18 + rm task17 task18 task19 task20 diff --git a/set3/task20.c b/set3/task20.c new file mode 100644 index 0000000..7ab24de --- /dev/null +++ b/set3/task20.c @@ -0,0 +1,64 @@ +#include "../lib/lib.h" +#include "../lib/lib2.h" +#include "../lib/lib3.h" +#include <time.h> + +#define CHALLENGE20_FILE_NR 60 +int main() +{ + int i; + char **file = malloc(sizeof(char *)*CHALLENGE20_FILE_NR); + int length_file[CHALLENGE20_FILE_NR]; + int length[CHALLENGE20_FILE_NR]; + char **plaintext= malloc(sizeof(char *)*CHALLENGE20_FILE_NR); + char **ciphertext= malloc(sizeof(char *)*CHALLENGE20_FILE_NR); + char filename[] = "./task20_data/task20_00"; + + char nonce[16]; + int min_length = 9999999; + generate_random_bytes(key, 16); + generate_random_bytes(nonce, 16); + + for(i=0;i<CHALLENGE20_FILE_NR;i++) { + filename[strlen(filename)-1] = ((i % 10)+ '0'); + filename[strlen(filename)-2] = ((i / 10) + '0'); + length_file[i] = read_base64_file(filename, &file[i]); + plaintext[i] = malloc(length_file[i]); + length[i] = decode_base64(file[i], plaintext[i]); + if(length[i] < min_length) + min_length = length[i]; + ciphertext[i] = malloc(length[i]); + aes_ctr(plaintext[i], length[i], ciphertext[i], key, nonce); + } + + printf("smallest string : %i\n", min_length); + // let the cracking begin + + // merge all the chunks and then do the vingere chiffre break + // so we have 60 blocks and the key length is min_length + // no need + char *merged = malloc(min_length*CHALLENGE20_FILE_NR); + for(i=0;i<CHALLENGE20_FILE_NR;i++) { + memcpy(&merged[i*min_length], ciphertext[i], min_length); + } + + char **blocks = transpose_blocks(merged, min_length, + (min_length*CHALLENGE20_FILE_NR)); + + // run the normal ceasr chiffre attack + char restored_keystream[min_length]; + struct key_and_freq tmp_NOT_USED_HERE; + for(i=0;i<min_length;i++) { + restored_keystream[i] = brute_force_single_byte_xor( + blocks[i], min_length, &tmp_NOT_USED_HERE); + } + + // xor ciphertext against keystream + char *restored_plaintext = malloc(min_length); + for(i=0;i<CHALLENGE20_FILE_NR;i++) { + xor_string(ciphertext[i], restored_keystream, restored_plaintext, + min_length, min_length); + printf("%s\n", plaintext[i]); + printf("%s\n", restored_plaintext); + } +} |