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trezor-firmware/crypto/chacha_drbg.h

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/*
* This file is part of the Trezor project, https://trezor.io/
*
* Copyright (c) SatoshiLabs
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __CHACHA_DRBG__
#define __CHACHA_DRBG__
#include "chacha20poly1305/chacha20poly1305.h"
#include "sha2.h"
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// A very fast deterministic random bit generator based on CTR_DRBG in NIST SP
// 800-90A. Chacha is used instead of a block cipher in the counter mode, SHA256
// is used as a derivation function. The highest supported security strength is
// at least 256 bits. Reseeding is left up to caller.
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// Length of inputs of chacha_drbg_init (entropy and nonce) or
// chacha_drbg_reseed (entropy and additional_input) that fill exactly
// block_count blocks of hash function in derivation_function. There is no need
// the input to have this length, it's just an optimalization.
#define CHACHA_DRBG_OPTIMAL_RESEED_LENGTH(block_count) \
((block_count) * SHA256_BLOCK_LENGTH - 1 - 4 - 9)
// 1 = sizeof(counter), 4 = sizeof(output_length) in
// derivation_function, 9 is length of SHA256 padding of message
// aligned to bytes
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typedef struct _CHACHA_DRBG_CTX {
ECRYPT_ctx chacha_ctx;
uint32_t reseed_counter;
} CHACHA_DRBG_CTX;
void chacha_drbg_init(CHACHA_DRBG_CTX *ctx, const uint8_t *entropy,
size_t entropy_length, const uint8_t *nonce,
size_t nonce_length);
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void chacha_drbg_generate(CHACHA_DRBG_CTX *ctx, uint8_t *output,
size_t output_length);
void chacha_drbg_reseed(CHACHA_DRBG_CTX *ctx, const uint8_t *entropy,
size_t entropy_length, const uint8_t *additional_input,
size_t additional_input_length);
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#endif // __CHACHA_DRBG__