* @param ctx an AVCAST5 context
* @param key a key of 5,6,...16 bytes used for encryption/decryption
* @param key_bits number of keybits: possible are 40,48,...,128
+ * @return 0 on success, less than 0 on failure
*/
int av_cast5_init(struct AVCAST5 *ctx, const uint8_t *key, int key_bits);