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/*
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*******************************************************************************
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\file belt_cfb.c
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\brief STB 34.101.31 (belt): CFB encryption
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\project bee2 [cryptographic library]
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\author (C) Sergey Agievich [agievich@{bsu.by|gmail.com}]
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\created 2012.12.18
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\version 2020.03.24
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\license This program is released under the GNU General Public License
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version 3. See Copyright Notices in bee2/info.h.
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*******************************************************************************
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*/
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#include "bee2/core/blob.h"
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#include "bee2/core/err.h"
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#include "bee2/core/mem.h"
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#include "bee2/core/util.h"
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#include "bee2/crypto/belt.h"
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#include "belt_lcl.h"
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/*
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*******************************************************************************
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Шифрование в режиме CFB
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*******************************************************************************
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*/
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typedef struct
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{
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u32 key[8]; /*< форматированный ключ */
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octet block[16]; /*< блок гаммы */
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size_t reserved; /*< резерв октетов гаммы */
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} belt_cfb_st;
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1
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size_t beltCFB_keep()
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{
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return sizeof(belt_cfb_st);
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}
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1
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void beltCFBStart(void* state, const octet key[], size_t len,
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const octet iv[16])
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{
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belt_cfb_st* st = (belt_cfb_st*)state;
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1
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ASSERT(memIsDisjoint2(iv, 16, state, beltCFB_keep()));
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1
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beltKeyExpand2(st->key, key, len);
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1
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beltBlockCopy(st->block, iv);
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st->reserved = 0;
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}
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void beltCFBStepE(void* buf, size_t count, void* state)
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{
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belt_cfb_st* st = (belt_cfb_st*)state;
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ASSERT(memIsDisjoint2(buf, count, state, beltCFB_keep()));
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// есть резерв гаммы?
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1
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if (st->reserved)
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{
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1
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if (st->reserved >= count)
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{
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0
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memXor2(st->block + 16 - st->reserved, buf, count);
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0
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memCopy(buf, st->block + 16 - st->reserved, count);
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0
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st->reserved -= count;
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return;
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}
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1
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memXor2(st->block + 16 - st->reserved, buf, st->reserved);
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1
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memCopy(buf, st->block + 16 - st->reserved, st->reserved);
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1
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count -= st->reserved;
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buf = (octet*)buf + st->reserved;
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st->reserved = 0;
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}
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// цикл по полным блокам
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1
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while (count >= 16)
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{
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1
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beltBlockEncr(st->block, st->key);
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1
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beltBlockXor2(st->block, buf);
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beltBlockCopy(buf, st->block);
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buf = (octet*)buf + 16;
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1
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count -= 16;
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}
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// неполный блок?
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1
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if (count)
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{
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1
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beltBlockEncr(st->block, st->key);
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1
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memXor2(st->block, buf, count);
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1
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memCopy(buf, st->block, count);
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1
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st->reserved = 16 - count;
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}
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}
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1
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void beltCFBStepD(void* buf, size_t count, void* state)
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{
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1
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belt_cfb_st* st = (belt_cfb_st*)state;
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1
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ASSERT(memIsDisjoint2(buf, count, state, beltCFB_keep()));
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// есть резерв гаммы?
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1
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if (st->reserved)
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{
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1
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if (st->reserved >= count)
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{
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0
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memXor2(buf, st->block + 16 - st->reserved, count);
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0
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memXor2(st->block + 16 - st->reserved, buf, count);
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st->reserved -= count;
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return;
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}
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1
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memXor2(buf, st->block + 16 - st->reserved, st->reserved);
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1
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memXor2(st->block + 16 - st->reserved, buf, st->reserved);
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1
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count -= st->reserved;
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1
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buf = (octet*)buf + st->reserved;
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1
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st->reserved = 0;
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}
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// цикл по полным блокам
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1
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while (count >= 16)
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{
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1
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beltBlockEncr(st->block, st->key);
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1
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beltBlockXor2(buf, st->block);
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beltBlockXor2(st->block, buf);
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1
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buf = (octet*)buf + 16;
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1
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count -= 16;
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}
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// неполный блок?
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1
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if (count)
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{
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1
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beltBlockEncr(st->block, st->key);
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1
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memXor2(buf, st->block, count);
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1
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memXor2(st->block, buf, count);
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1
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st->reserved = 16 - count;
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}
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}
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1
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err_t beltCFBEncr(void* dest, const void* src, size_t count,
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const octet key[], size_t len, const octet iv[16])
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{
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void* state;
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// проверить входные данные
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1
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if (len != 16 && len != 24 && len != 32 ||
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!memIsValid(src, count) ||
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1
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!memIsValid(key, len) ||
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!memIsValid(iv, 16) ||
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1
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!memIsValid(dest, count))
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return ERR_BAD_INPUT;
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// создать состояние
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1
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state = blobCreate(beltCFB_keep());
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1
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if (state == 0)
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0
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return ERR_OUTOFMEMORY;
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// зашифровать
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beltCFBStart(state, key, len, iv);
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1
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memMove(dest, src, count);
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1
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beltCFBStepE(dest, count, state);
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// завершить
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1
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blobClose(state);
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1
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return ERR_OK;
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}
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149
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150
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1
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err_t beltCFBDecr(void* dest, const void* src, size_t count,
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151
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const octet key[], size_t len, const octet iv[16])
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152
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{
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153
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void* state;
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154
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// проверить входные данные
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1
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if (len != 16 && len != 24 && len != 32 ||
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1
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!memIsValid(src, count) ||
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157
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1
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!memIsValid(key, len) ||
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158
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1
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!memIsValid(iv, 16) ||
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159
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1
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!memIsValid(dest, count))
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0
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return ERR_BAD_INPUT;
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// создать состояние
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1
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state = blobCreate(beltCFB_keep());
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1
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if (state == 0)
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0
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return ERR_OUTOFMEMORY;
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// расшифровать
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1
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beltCFBStart(state, key, len, iv);
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1
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memMove(dest, src, count);
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1
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beltCFBStepD(dest, count, state);
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// завершить
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1
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blobClose(state);
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1
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return ERR_OK;
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172
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}
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173
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agievich