Thread: How to decrypt / encrypt using libgcrypt ? (ARC4)

Howdy ,..

I'm reaading libgcrypt manual but
I cannot understand what values i should use in encrypt /decrypt when using gcry_cipher_encrypt :

for example when i run this code :

Code:

#include <stdio.h>
#include <gcrypt.h>
#include <assert.h>

int main()
{

  gcry_cipher_hd_t handle;
  gcry_error_t err = 0;
  char * plain_text ;
  char * out ;
  char * deout ;

  size_t size_of_plain = sizeof(char) * 6;
  size_t size_of_crypt = sizeof(char) * 601;
  plain_text = malloc (size_of_plain);
  out =  malloc (size_of_crypt);
  deout = malloc (size_of_crypt);
  assert(plain_text);
  assert(out);
  assert(deout);

  strcpy(plain_text , "Secret");
  

  gcry_check_version (NULL);
  gcry_control( GCRYCTL_DISABLE_SECMEM_WARN );
  gcry_control( GCRYCTL_INIT_SECMEM, 16384, 0 );


       {


       err = gcry_cipher_open (&handle, GCRY_CIPHER_ARCFOUR,GCRY_CIPHER_MODE_STREAM,0);
 
       if (err)
         {
           fprintf (stderr, "Failure: &#37;s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));
           fprintf (stdout, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));

         }
	err = gcry_cipher_setkey (handle, "This is really strange , i read the documentation i googled for two days and nothing , i can't encrypt && decrypt",128);
	if (err)
         {
           fprintf (stderr, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));
           fprintf (stdout, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));

         }
     }
  err =  gcry_cipher_encrypt (handle,
          (unsigned char *)out, sizeof(out), (const unsigned char *)plain_text,sizeof plain_text);
if (err)
         {
           fprintf (stderr, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));
           fprintf (stdout, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));

         }
  printf(" out :%s ||| plain text %s\n",out, plain_text);
err =  gcry_cipher_encrypt (handle,
          (unsigned char *)deout, sizeof deout, (const unsigned char *)out,sizeof out);
if (err)
         {
           fprintf (stderr, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));
           fprintf (stdout, "Failure: %s/%s\n",
                    gcry_strsource (err),
                    gcry_strerror (err));

         }
  printf("deout: %s ||| out: %s ||| plain text: %s\n",deout, out,plain_text);
  
  free(plain_text);
  free(out);
  free(deout);
  gcry_cipher_close(handle);
  return 0;

}

i get the next output :

Code:

��g�zB�QK]o
��A�R����       2�9�

while i should get according to wikipedia :

Code:

45A01F645FC35B383552544B9BF5
Attack at down

What should i do to fix it ?