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; aes256-ctr.inc - AES256 Counter Mode |
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; |
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; Copyright (C) 2016 Ivan Baravy (dunkaist) |
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; |
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; This program is free software: you can redistribute it and/or modify |
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; it under the terms of the GNU General Public License as published by |
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; the Free Software Foundation, either version 3 of the License, or |
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; (at your option) any later version. |
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; |
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; This program is distributed in the hope that it will be useful, |
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; but WITHOUT ANY WARRANTY; without even the implied warranty of |
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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; GNU General Public License for more details. |
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; |
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; You should have received a copy of the GNU General Public License |
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; along with this program. If not, see . |
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struct aes256_ctr_context aes256_context |
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counter rb AES256_BLOCKSIZE |
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output rb AES256_BLOCKSIZE ; counter after aes_crypt |
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ends |
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proc aes256_ctr_init _counter |
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push ebx esi edi |
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mcall 68, 12, sizeof.aes256_ctr_context |
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; handle errors |
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mov ecx, AES256_BLOCKSIZE/4 |
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mov esi, [_counter] |
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lea edi, [eax + aes256_ctr_context.counter] |
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rep movsd |
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; rep movsd is slow, but we don't care while init |
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pop edi esi ebx |
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ret |
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endp |
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proc aes256_ctr_crypt _ctx, _in, _out |
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push ebx esi edi |
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DEBUGF 1,'plain : ' |
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stdcall dump_hex, [_in], 4 |
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mov esi, [_ctx] |
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lea eax, [esi + aes256_ctr_context.key] |
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lea ebx, [esi + aes256_ctr_context.counter] |
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lea ecx, [esi + aes256_ctr_context.output] |
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stdcall aes256_encrypt, eax, ebx, ecx ; Key, in, out |
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mov ebx, [_ctx] |
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mov esi, [_in] |
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mov edi, [_out] |
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mov eax, [esi + 4*0] |
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xor eax, dword[ebx + aes256_ctr_context.output + 4*0] |
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mov [edi + 4*0], eax |
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mov eax, [esi + 4*1] |
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xor eax, dword[ebx + aes256_ctr_context.output + 4*1] |
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mov [edi + 4*1], eax |
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mov eax, [esi + 4*2] |
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xor eax, dword[ebx + aes256_ctr_context.output + 4*2] |
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mov [edi + 4*2], eax |
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mov eax, [esi + 4*3] |
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xor eax, dword[ebx + aes256_ctr_context.output + 4*3] |
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mov [edi + 4*3], eax |
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; Increment counter |
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mov esi, [_ctx] |
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mov eax, dword[esi + aes256_ctr_context.counter + 4*0] |
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mov ebx, dword[esi + aes256_ctr_context.counter + 4*1] |
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mov ecx, dword[esi + aes256_ctr_context.counter + 4*2] |
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mov edx, dword[esi + aes256_ctr_context.counter + 4*3] |
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bswap eax |
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bswap ebx |
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bswap ecx |
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bswap edx |
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inc edx |
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adc ecx, 0 |
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adc ebx, 0 |
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adc eax, 0 |
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bswap eax |
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bswap ebx |
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bswap ecx |
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bswap edx |
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mov dword[esi + aes256_ctr_context.counter + 4*0], eax |
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mov dword[esi + aes256_ctr_context.counter + 4*1], ebx |
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mov dword[esi + aes256_ctr_context.counter + 4*2], ecx |
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mov dword[esi + aes256_ctr_context.counter + 4*3], edx |
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DEBUGF 1,'cipher : ' |
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stdcall dump_hex, [_out], 4 |
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pop edi esi ebx |
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ret |
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endp |