cts_decr
ret = cts_decr(key, ivec, data, num_data, input_length);
cts_decr(krb5_key key, const krb5_data *ivec, krb5_crypto_iov *data,
ret = cts_decr(key, ivec, data, num_data, input_length);
cts_decr(krb5_key key, const krb5_data *ivec, krb5_crypto_iov *data,