-extern bool cipher_gcm_encrypt(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen) __attribute__ ((__warn_unused_result__));
-extern bool cipher_gcm_encrypt_start(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen) __attribute__ ((__warn_unused_result__));
-extern bool cipher_gcm_encrypt_finish(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen) __attribute__ ((__warn_unused_result__));
-extern bool cipher_gcm_decrypt(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen) __attribute__ ((__warn_unused_result__));
-extern bool cipher_gcm_decrypt_start(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen) __attribute__ ((__warn_unused_result__));
-extern bool cipher_gcm_decrypt_finish(cipher_t *, const void *indata, size_t inlen, void *outdata, size_t *outlen) __attribute__ ((__warn_unused_result__));