public byte[] decrypt(byte[] cipher, byte[] key, byte[] ivec, int usage)
     throws KrbApErrException, KrbCryptoException {
   try {
     return Des3.decrypt(key, usage, ivec, cipher, 0, cipher.length);
   } catch (GeneralSecurityException e) {
     KrbCryptoException ke = new KrbCryptoException(e.getMessage());
     ke.initCause(e);
     throw ke;
   }
 }