Function generate_header_padding

common/sphinx.c:287–316

}

static void generate_header_padding(void *dst, size_t dstlen,
				    size_t fixed_size,
				    const struct sphinx_path *path,
				    struct hop_params *params)
{
	struct secret key;
	size_t fillerStart, fillerEnd, fillerSize;

	memset(dst, 0, dstlen);
	for (int i = 0; i < tal_count(path->hops) - 1; i++) {
		subkey_from_hmac("rho", &params[i].secret, &key);

		/* Sum up how many bytes have been used by previous hops,
		 * that gives us the start in the stream */
		fillerSize = 0;
		for (int j = 0; j < i; j++)
			fillerSize += sphinx_hop_size(&path->hops[j]);
		fillerStart = fixed_size - fillerSize;

		/* The filler will dangle off of the end by the current
		 * hop-size, we'll make sure to copy it into the correct
		 * position in the next step. */
		fillerEnd = fixed_size + sphinx_hop_size(&path->hops[i]);

		/* Apply the cipher-stream to the part of the filler that'll
		 * be added by this hop */
		xor_cipher_stream_off(&key, fillerStart,
				      dst, fillerEnd - fillerStart);
	}
}

static void generate_prefill(void *dst, size_t dstlen,
			     size_t fixed_size,