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#include "lib4.h"
#include "lib3.h"
#include "lib2.h"
#include "lib.h"
/**
* encrypt always with the same key, same nonce?
*
**/
int aes_ctr_edit(char *ciphertext, int ciphertext_length, int offset, char *newtext)
{
// do not allow greater ciphertexts
if((strlen(newtext)+offset) > ciphertext_length)
return 1;
// insert newtext at offset and reencrpyt
char *plaintext = malloc(ciphertext_length);
aes_ctr(ciphertext, ciphertext_length, plaintext, key, nonce);
memcpy(&plaintext[offset], newtext, strlen(newtext));
aes_ctr(plaintext, ciphertext_length, ciphertext, key, nonce);
return 0;
}
void sha1_hmac(unsigned int *mac, unsigned char *message, unsigned int msg_len, unsigned char *key,
unsigned int key_len)
{
char *res = malloc(msg_len + key_len);
memcpy(res, key, key_len);
memcpy(&res[key_len], message, msg_len);
SHA1Context sh;
SHA1Reset(&sh);
SHA1Input(&sh, res, (msg_len + key_len));
SHA1Result(&sh);
memcpy(mac, &(sh.Message_Digest), 20);
}
int sha1_hmac_verify(unsigned int *mac, unsigned char *msg, unsigned int msg_len,
unsigned char *key, unsigned int key_len)
{
unsigned int com_mac[5];
sha1_hmac(com_mac, msg, msg_len, key, key_len);
return !memcmp(com_mac, mac, 20);
}
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