Hi there. Read this letter further only if you have patience to read the attached C code to.
Thanks, so you have patience.
So, I'd like to know, if this code is ok, does it produce a correct ciphertext. And if it does, can I write the decrypting function just by changing the functions.
EVP_Encrypt_Init to EVP_Decrypt_Init
EVP_Encrypt_Update to EVP_Decrypt_Update and
EVP_Encrypt_Final to EVP_Decrypt_Final ?
The copy string copies from source a substring (from the position begin to position end) into target.
void copy_string(unsigned char *source, int source_length, unsigned char** target, int begin, int end)
//Note:
//the position end is included only
{
*target = NULL;
if ((source!=NULL) && (begin>=0) && (end>begin))
{
if (end>source_length)
{
end = source_length;
}
source = source + begin;
*target = (unsigned char *) malloc (end-begin);
for (int i = begin; i<end; i++)
{
**target = *source;
(*target)++;
source++;
}
//**target = '\0';
*target = *target - (end-begin);
source = source - end;
}
}
int EVP_DES3_encrypt(unsigned char *in, int in_length, unsigned char *password, int password_length, unsigned char** out)
{
unsigned char *key = NULL;
unsigned char *iv = NULL;
unsigned char *OUT = NULL;
unsigned char *in_piece = NULL;
int out_length = 0;
int out_piece_length = 0;
int piece_length = 512;
int number_of_pieces = in_length / piece_length;
int i = 0;
EVP_CIPHER_CTX ctx;
EVP_CIPHER *cipher_type = EVP_des_ede3_cbc();
EVP_MD *hash_type = EVP_md5();
key = (unsigned char*) malloc (EVP_MAX_KEY_LENGTH);
iv = (unsigned char*) malloc (EVP_MAX_IV_LENGTH);
OUT = (unsigned char*) malloc (in_length+2*piece_length);
printf("Lefoglalva:%d\n",in_length+2*piece_length);
if ((in_length % piece_length) !=0)
{
number_of_pieces++;
}
EVP_BytesToKey(cipher_type, hash_type, NULL, password, password_length, 1, key, iv);
EVP_EncryptInit(&ctx, cipher_type, key, iv);
while (i<number_of_pieces)
{
copy_string(in,in_length,&in_piece,i*piece_length,(i+1)*piece_length);
EVP_EncryptUpdate(&ctx,OUT,&out_piece_length,in_piece,piece_length);
out_length+=out_piece_length;
i++;
//free(in_piece);
}
EVP_EncryptFinal(&ctx,OUT,&out_piece_length);
out_length+=out_piece_length;
*out = OUT;
// free(OUT);
free(key);
free(iv);
// printf("Szukseges:%d\n",out_length);
return(out_length);
}
Thanks again.
andras
