1/*
2 * Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#ifndef OSSL_CRYPTO_CHACHA_H
11#define OSSL_CRYPTO_CHACHA_H
12
13#include <stddef.h>
14
15/*
16 * ChaCha20_ctr32 encrypts |len| bytes from |inp| with the given key and
17 * nonce and writes the result to |out|, which may be equal to |inp|.
18 * The |key| is not 32 bytes of verbatim key material though, but the
19 * said material collected into 8 32-bit elements array in host byte
20 * order. Same approach applies to nonce: the |counter| argument is
21 * pointer to concatenated nonce and counter values collected into 4
22 * 32-bit elements. This, passing crypto material collected into 32-bit
23 * elements as opposite to passing verbatim byte vectors, is chosen for
24 * efficiency in multi-call scenarios.
25 */
26void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,
27 size_t len, const unsigned int key[8],
28 const unsigned int counter[4]);
29/*
30 * You can notice that there is no key setup procedure. Because it's
31 * as trivial as collecting bytes into 32-bit elements, it's reckoned
32 * that below macro is sufficient.
33 */
34#define CHACHA_U8TOU32(p) ( \
35 ((unsigned int)(p)[0]) | ((unsigned int)(p)[1]<<8) | \
36 ((unsigned int)(p)[2]<<16) | ((unsigned int)(p)[3]<<24) )
37
38#define CHACHA_KEY_SIZE 32
39#define CHACHA_CTR_SIZE 16
40#define CHACHA_BLK_SIZE 64
41
42#endif
43