Tyler Durden wrote:
Hello, I write the next c programming code that allow to do a test of
encryption and decryption.
I understand that I do bad, because the EVP_DecryptionFinal return 0
therefore the decrypted data are not match that the original data.
Please help me. Thaks very much
The code is this. I am using Microsoft windows with VC 6.
#include <stdio.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/x509v3.h>
#define DATA_LENGTH (int) 29
int encrypt( unsigned char *key, unsigned char *originalData, int length,
unsigned char **cipheredData )
{
EVP_CIPHER_CTX ctx;
const EVP_CIPHER *des3 = EVP_des_ede3();
*cipheredData = new unsigned char[length + EVP_CIPHER_block_size( des3
) - 1];
unsigned char *cipheredDataAux = *cipheredData;
int cipheredDataLength = 0;
EVP_CIPHER_CTX_init( &ctx );
if( EVP_EncryptInit( &ctx, des3, key, NULL ) == 0 )
ERR_print_errors_fp( stderr );
int cipheredNum = 0;
printf( "The original Data is: %s \nand the size is: %d\n\n",
originalData,
length );
while( cipheredDataLength < length )
{
if( EVP_EncryptUpdate( &ctx,
&cipheredDataAux[cipheredNum],
&cipheredNum,
originalData,
length -
cipheredNum ) == 0 )
ERR_print_errors_fp( stderr );
cipheredDataLength += cipheredNum;
}
don't use the while-loop, on call to EVP_EncryptUpdate is enough here
printf( "The ciphered Data is: %s \nand the size is: %d\n\n",
cipheredDataAux,
cipheredDataLength );
cipheredNum = 0;
if( EVP_EncryptFinal( &ctx, &cipheredDataAux[cipheredDataLength],
&cipheredNum ) == 0 )
ERR_print_errors_fp( stderr );
cipheredDataLength += cipheredNum;
printf( "The ciphered Data is: %s \nand the size is: %d\n\n",
cipheredDataAux,
cipheredDataLength );
EVP_CIPHER_CTX_cleanup (& ctx);
return cipheredDataLength;
}
int decrypt( unsigned char *key, unsigned char *cipheredData, int length,
unsigned char **decipheredData )
{
EVP_CIPHER_CTX ctx;
const EVP_CIPHER *des3 = EVP_des_ede3();
*decipheredData = new unsigned char[length + EVP_CIPHER_block_size(
des3 )];
unsigned char *decipheredDataAux = *decipheredData;
int decipheredDataLength = 0;
EVP_CIPHER_CTX_init( &ctx );
if( EVP_DecryptInit( &ctx, des3, key, NULL ) == 0 )
ERR_print_errors_fp( stderr );
int decipheredNum = 0;
printf( "The ciphered Data is: %s \nand the size is: %d\n\n",
cipheredData,
length );
while( decipheredDataLength < length )
{
if( EVP_DecryptUpdate( &ctx,
&decipheredDataAux[decipheredNum],
&decipheredNum,
cipheredData,
length -
decipheredNum ) == 0 )
ERR_print_errors_fp( stderr );
decipheredDataLength += decipheredNum;
}
again, the while-loop is unneccesary. One invocation of
EVP_DecryptUpdate + EVP_DecryptFinal is enough
Nils
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