Using libgcrypt1.2.0 for 3DES, ECB mode of encryption/decryption.

[Vishal Rao]

Hi,

Do not use strlen() on plaintext or ciphertext! Its not really text!
If there happens to be a zero in the bytes your strlen will return a
shorter value!

Cheers,
Vishal


On Thu, 9 Dec 2004 09:58:04 -0500, Madhavi.Gandavarapu at equifax.com
<Madhavi.Gandavarapu at equifax.com> wrote:
> 
> 
> Hi,
> 
> I have a string that I am trying to encrypt using 3DES,ECB mode.  I have a
> specific 24 byte key that I need to use to encrypt or decrypt.
> I am not getting good encrypted string back, since I can't even decrypt what I
> encrypted with the same key and same library.
> 
> Can you point me to what I am doing wrong here.
> 
> Here is the code segment.
> 
> unsigned char enc_key[24] =
> {0x12,0x34,0x51,0x23,0x45,0x12,0x34,0x51,0x15,0x43,0x21,0x54,0x32,0x15,0x43,0x21,0x45,0x12,0x34,0x51,0x12,
> 0x34,0x51,0x23};
> 
> static int do_encrypt(unsigned char* dest,unsigned char* src)
> {
>    //GCRY_CIPHER_3DES is the algorithm type
>    //GCRY_CIPHER_MODE_ECB is the algorithem mode
>    //0(zero) is the flags value to send
>    int retVal =0;
>    gcry_cipher_hd_t hd;
> 
>    int keylen;
>    int i =0,x=0;
>    gcry_error_t err = 0;
> 
>    keylen = gcry_cipher_get_algo_keylen(GCRY_CIPHER_3DES);
>    if (!keylen)
>    {
> //    fail ("algo %d, mode %d, gcry_cipher_get_algo_keylen failed\n", algo,
> mode);
>       logf(&bLog, LF_ERROR, "algo %s, mode %s, gcry_cipher_get_algo_keylen
> failed","GCRY_CIPHER_3DES" ,"GCRY_CIPHER_MODE_ECB" );
>       retVal = -1;
>       return retVal;
>    }
>    if (keylen < 40 / 8 || keylen > 32)
>    {
> //    fail ("algo %d, mode %d, keylength problem (%d)\n", algo, mode, keylen);
>       logf(&bLog, LF_ERROR, "algo %s, mode %s, keylength problem
> (%d)","GCRY_CIPHER_3DES" ,"GCRY_CIPHER_MODE_ECB",keylen );
>       retVal = -1;
>       return retVal;
>    }
>    err = gcry_cipher_open (&hd, GCRY_CIPHER_3DES, GCRY_CIPHER_MODE_ECB, 0);
>    if (err)
>    {
> //    fail ("algo %d, mode %d, grcy_open_cipher failed: %s\n", algo, mode,
> gpg_strerror (err));
>       logf(&bLog, LF_ERROR, "algo %s, mode %s, grcy_open_cipher failed:
> %s","GCRY_CIPHER_3DES" ,"GCRY_CIPHER_MODE_ECB",gpg_strerror(err)
> );
>       return err;
> 
>  }
>    err = gcry_cipher_setkey (hd, &enc_key, keylen);
>    if (err)
>    {
> //    fail ("algo %d, mode %d, gcry_cipher_setkey failed: %s\n",  algo, mode,
> gpg_strerror (err));
>       logf(&bLog, LF_ERROR, "algo %s, mode %s, gcry_cipher_setkey failed:
> %s","GCRY_CIPHER_3DES" ,"GCRY_CIPHER_MODE_ECB",gpg_strerror(er
> r));
>       gcry_cipher_close (hd);
>       return err;
>    }
>    //err = gcry_cipher_encrypt (hd, dest, strlen(dest), NULL,strlen(dest));
>    err = gcry_cipher_encrypt (hd, dest, strlen(dest), src, strlen(src));
>    if (err)
>    {
> //    fail ("algo %d, mode %d, gcry_cipher_encrypt failed: %s\n", algo, mode,
> gpg_strerror (err));
>       logf(&bLog, LF_ERROR, "algo %s, mode %s, gcry_cipher_encrypt failed:
> %s","GCRY_CIPHER_3DES" ,"GCRY_CIPHER_MODE_ECB",gpg_strerror(e
> rr));
>       gcry_cipher_close (hd);
>       return err;
>    }
>    i =0; x=0;
>    if((x = (strlen(dest)%bsize)))
>    {
>       x = (bsize - x);
>       for(i = 0; i < x; i++)
>          strcat(dest," ");
>    }
> 
>    err = gcry_cipher_decrypt (hd, dest, strlen(dest), dest, strlen(dest));
>    if (err)
>    {
> //    fail ("algo %d, mode %d, gcry_cipher_decrypt failed: %s\n", algo, mode,
> gpg_strerror (err));
>       logf(&bLog, LF_ERROR, "algo %s, mode %s, gcry_cipher_decrypt failed:
> %s","GCRY_CIPHER_3DES" ,"GCRY_CIPHER_MODE_ECB",gpg_strerror(e
> rr));
>       gcry_cipher_close (hd);
>       return err;
>    }
> 
>    gcry_cipher_close (hd);
> 
> Thanks and Regards
> Madhavi
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