Cryptographic tools

Any functions that return string representations of bytes in hexadecimal format will always be formatted with no leading 0x and lower case letters

Encodes an unsigned char * into base64. User is responsible for freeing the char * that is returned.

char *b64_encode(const unsigned char *s, size_t sz);

Decodes a base64 encoded set of bytes into an unsigned char *. User is responsible for freeing the unsigned char * that is returned. decode_sz is an optional argument in case you need to know the size of the decoded data, otherwise you can just pass NULL.

unsigned char *b64_decode(const char *s, size_t sz, size_t *decode_sz);

Encodes an array of bytes into a string in hex representation. For example, converts [0xDE, 0xAD, 0xBE, 0xEF] into "deadbeef". User is responsible for freeing the returned string

const char *hex_encode(const unsigned char *hex, size_t sz);
 
// Example
unsigned char h[4] = {
    0xde, 0xad, 0xbe, 0xef
};
const char *s = hex_encode(h, 4);
assert(strcmp(s, "deadbeef") == 0);
free(s);

Decodes a string of characters representing hexadecimal bytes into an array of unsigned char. Characters can be in upper or lower case, and can start with a leading 0x or not. For example, converts "DEADBEEF" into [0xde, 0xad, 0xbe, 0xef]. User is reponsible for the freeing of the returned byte array

unsigned char *hex_decode(const char *orig, size_t *sz);
 
// Example
unsigned char *s = hex_decode("DEADBEEF", &s_sz);
unsigned char h[4] = {
    0xDE, 0xAD, 0xBE, 0xEF
};
for (size_t i = 0; i < 4; ++i) {
    assert(s[i] == h[i]);
}
free(s);

Converts an array of unsigned char into a string based on the ASCII values of each byte. User is responsible for freeing the returned string.

const char *hex_to_str(const unsigned char *hex, size_t sz);

Performs a repeating-key XOR encryption on an array of bytes. User is responsible for freeing the returned array

const unsigned char* repeating_key_xor(const unsigned char* s, size_t s_sz, const unsigned char* key, size_t k_sz);

Performs a repeating-key XOR encryption on a string. Returns the encrypted string as an array of bytes. User is responsible for freeing the returned array

const unsigned char *repeating_key_xor_s(const char* s, const char* key);

Calculates the Hamming Distance (the number of differing bits) between two arrays of unsigned bytes

unsigned int hamming_distance(unsigned char *a, unsigned char *b);

Calculates the Hamming Distance (the number of differing bits) between two strings

unsigned int hamming_distance_s(const char *a, const char *b);