wolfSSL HPKE example

hpke.c

#include <stdio.h>
#include <stdint.h>
#include <stdbool.h>
#include <wolfssl/options.h>
#include <wolfssl/wolfcrypt/settings.h>
#include <wolfssl/wolfcrypt/hpke.h>

void main()
{
	int ret = 0;
	int rngRet = 0;
	Hpke hpke[1];
	WC_RNG rng[1];
	const char* start_text = "this is a test";
	const char* info_text = "info";
	const char* aad_text = "aad";
	byte ciphertext[MAX_HPKE_LABEL_SZ];
	byte plaintext[MAX_HPKE_LABEL_SZ];
	void* receiverKey = NULL;
	void* ephemeralKey = NULL;
	uint8_t pubKey[HPKE_Npk_MAX]; /* public key */
	word16 pubKeySz = (word16)sizeof(pubKey);

	ret = wc_HpkeInit(hpke, DHKEM_X25519_HKDF_SHA256, HKDF_SHA256,
    	HPKE_AES_128_GCM, NULL); /* or HPKE_AES_256_GCM */

	if (ret != 0)
    	return ret;

	rngRet = ret = wc_InitRng(rng);

	if (ret != 0)
    	return ret;

	/* generate the keys */
	if (ret == 0)
    	ret = wc_HpkeGenerateKeyPair(hpke, &ephemeralKey, rng);

	if (ret == 0)
    	ret = wc_HpkeGenerateKeyPair(hpke, &receiverKey, rng);

	/* seal */
	if (ret == 0)
    	ret = wc_HpkeSealBase(hpke, ephemeralKey, receiverKey,
        	(byte*)info_text, (word32)XSTRLEN(info_text),
        	(byte*)aad_text, (word32)XSTRLEN(aad_text),
        	(byte*)start_text, (word32)XSTRLEN(start_text),
        	ciphertext);

	/* export ephemeral key */
	if (ret == 0)
    	ret = wc_HpkeSerializePublicKey(hpke, ephemeralKey, pubKey, &pubKeySz);

	/* open with exported ephemeral key */
	if (ret == 0)
    	ret = wc_HpkeOpenBase(hpke, receiverKey, pubKey, pubKeySz,
        	(byte*)info_text, (word32)XSTRLEN(info_text),
        	(byte*)aad_text, (word32)XSTRLEN(aad_text),
        	ciphertext, (word32)XSTRLEN(start_text),
        	plaintext);

	if (ret == 0)
    	ret = XMEMCMP(plaintext, start_text, XSTRLEN(start_text));

	if (ephemeralKey != NULL)
    	wc_HpkeFreeKey(hpke->kem, ephemeralKey);

	if (receiverKey != NULL)
    	wc_HpkeFreeKey(hpke->kem, receiverKey);

	if (rngRet == 0)
    	wc_FreeRng(rng);

	if (ret == 0)
  	printf("SUCCESS");
}