Re: [Mcrypt-users] problem with CFB and other libraries?

[Jonathan D. <im...@ya...>]

Thanks for bringing this up.

I'll check to see what's happening here. There's some
outstanding bugs I really need to fix in the
mcrypt/mhash family, so I'll take this opportunity to
do a thorough work-through of the code.

--- Michael Medin <mi...@me...> wrote:

> I have tried to use crypto++ and openssl to get the
> same result as 
> mcrypt for a simple CFB crypto. The reason is I am
> trying to write a new 
> client for an existing server that use mcrypt, and
> mcrypt is not 
> "easily" available for windows.
> 
> The result from mcrypt is:
> 0xa7, 0x8f, 0x88, 0x4e, ...
> 
> Where-as the result from crypto++ and openssl is:
> 0xa7, 0x44, 0x24, 0x6e, ...
> 
> As you can see the first byte is the same but the
> following ones are 
> not. I am by no means an expert on neither mcrypt
> nor cryptography but 
> AFAIK using cfb should result in the same result so
> either I am doing 
> something wrong with mcrypt or something is wrong.
> 
> // Michael Medin
> 
> The code I use is the following:
> 
> #include <stdio.h>
> #include <mcrypt.h>
> #include <iostream>
> #include <iomanip>
> #include <sstream>
> 
> #include <crypto++/cryptlib.h>
> #include <crypto++/modes.h>
> #include <crypto++/des.h>
> #include <crypto++/aes.h>
> #include <crypto++/filters.h>
> #include <mcrypt.h>
> #include <openssl/ssl.h>
> #include <openssl/err.h>
> 
> unsigned char key[] = {0x31, 0x32, 0x33, 0x34, 0x35,
> 0x36, 0x37, 0x38, 
> 0x39, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36,
> 0x37, 0x38, 0x39, 0x30, 
> 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
> 0x39, 0x30, 0x31, 0x32}; 
> // 12345678901234567890123456789012
> unsigned char iv[] = {0x31, 0x32, 0x33, 0x34, 0x35,
> 0x36, 0x37, 0x38, 
> 0x39, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36}; //
> 1234567890123456
> unsigned char plain[] = {0x68, 0x65, 0x6c, 0x6c,
> 0x6f, 0x20, 0x77, 0x6f, 
> 0x72, 0x6c, 0x64}; // hello world
> 
> void print_it(char *title, unsigned char* buff, int
> len) {
>     int i;
>     printf("unsigned char %s[] = {", title);
>     for (i=0;i<len-1;i++) {
>         printf("0x%x, ", (unsigned char)buff[i]);
>     }
>     printf("0x%x", (unsigned char)buff[len-1]);
>     printf("} // %s\n", buff);
> }
> 
> void testCryptoPP() {
>     print_it("plain", plain, sizeof(plain));
>     CryptoPP::CFB_Mode< CryptoPP::AES >::Encryption
> encryptor(key, 
> sizeof(key), iv, sizeof(iv));
> 
>     unsigned char ciphertext[100];
>     for(int x=0;x<sizeof(plain);x++) {
>         encryptor.ProcessData(&ciphertext[x],
> (unsigned char*)&plain[x], 1);
>         ciphertext[x+1] = 0;
>     }
>     print_it("crypto", ciphertext, sizeof(plain));
> }
> void testMCrypt() {
>     MCRYPT td;
> 
>     td =
>
mcrypt_module_open(MCRYPT_RIJNDAEL_128,NULL,"cfb",NULL);
>     //int iv_size = mcrypt_enc_get_iv_size(td);
>     //printf("iv size: %d (%d)\n", iv_size,
> sizeof(iv));
> 
>     //int key_size = mcrypt_enc_get_key_size(td);
>     //printf("key size: %d (%d)\n", key_size,
> sizeof(key));
>    
>     mcrypt_generic_init(td,key,key_size,iv);
> 
>     print_it("plain", plain, sizeof(plain));
>     for(int x=0;x<sizeof(plain);x++)
>         mcrypt_generic(td,&plain[x],1);
>     print_it("mcrypt", plain, sizeof(plain));
> }
> void testOpenSSL() {
>     print_it("plain", plain, sizeof(plain));
>     EVP_CIPHER_CTX ctx;
>     EVP_CIPHER_CTX_init(&ctx);
>    
>
EVP_CipherInit_ex(&ctx,EVP_aes_256_cfb(),0,key,iv,1);
>     int ctout = 1024;
>     unsigned char ciphertext[ctout];
>    
>
EVP_CipherUpdate(&ctx,ciphertext,&ctout,plain,sizeof(plain));
>     print_it("openssl",ciphertext,ctout);
>     EVP_CIPHER_CTX_cleanup(&ctx);
> 
> }
> 
> 
> int main(int argv, char *argc[]) {
>     testOpenSSL();
>     testCryptoPP();
>     testMCrypt();
> }
> 
>
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