Function hkdf_two_keys

connectd/handshake.c:224–247

out1, out2 = HKDF(in1, in2)` */

/* out1, out2 = HKDF(in1, in2)` */
static void hkdf_two_keys(struct secret *out1, struct secret *out2,
			  const struct secret *in1,
			  const void *in2, size_t in2_size)
{
	/* BOLT #8:
	 *
	 *   * `HKDF(salt,ikm)`: a function defined in `RFC 5869`<sup>[3](#reference-3)</sup>,
	 *      evaluated with a zero-length `info` field
	 *      * All invocations of `HKDF` implicitly return 64 bytes
	 *        of cryptographic randomness using the extract-and-expand
	 *        component of the `HKDF`.
	 */
	struct secret okm[2];

	SUPERVERBOSE("# HKDF(0x%s,%s%s)",
		     tal_hexstr(tmpctx, in1, sizeof(*in1)),
		     in2_size ? "0x" : "zero",
		     tal_hexstr(tmpctx, in2, in2_size));
	BUILD_ASSERT(sizeof(okm) == 64);
	hkdf_sha256(okm, sizeof(okm), in1, sizeof(*in1), in2, in2_size,
		    NULL, 0);
	*out1 = okm[0];
	*out2 = okm[1];
}

static void le64_nonce(unsigned char *npub, u64 nonce)
{