/*

 * Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#ifndef OSSL_CRYPTO_CHACHA_H

#define OSSL_CRYPTO_CHACHA_H

#include <stddef.h>

/*

 * ChaCha20_ctr32 encrypts |len| bytes from |inp| with the given key and

 * nonce and writes the result to |out|, which may be equal to |inp|.

 * The |key| is not 32 bytes of verbatim key material though, but the

 * said material collected into 8 32-bit elements array in host byte

 * order. Same approach applies to nonce: the |counter| argument is

 * pointer to concatenated nonce and counter values collected into 4

 * 32-bit elements. This, passing crypto material collected into 32-bit

 * elements as opposite to passing verbatim byte vectors, is chosen for

 * efficiency in multi-call scenarios.

 */

void ChaCha20_ctr32(unsigned char *out, const unsigned char *inp,

                    size_t len, const unsigned int key[8],

                    const unsigned int counter[4]);

/*

 * You can notice that there is no key setup procedure. Because it's

 * as trivial as collecting bytes into 32-bit elements, it's reckoned

 * that below macro is sufficient.

 */

#define CHACHA_U8TOU32(p)  ( \

                ((unsigned int)(p)[0])     | ((unsigned int)(p)[1]<<8) | \

                ((unsigned int)(p)[2]<<16) | ((unsigned int)(p)[3]<<24)  )

#define CHACHA_KEY_SIZE         32

#define CHACHA_CTR_SIZE         16

#define CHACHA_BLK_SIZE         64

#endif