66 lines
1.8 KiB
C++
66 lines
1.8 KiB
C++
/*
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** Command & Conquer Renegade(tm)
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** Copyright 2025 Electronic Arts Inc.
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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 <http://www.gnu.org/licenses/>.
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*/
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#ifndef RC4_H
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#define RC4_H
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//
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// RC4.h - Implementation of RC4 encryption
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//
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// RC4 is a stream cypher. This means that it basically produces a stream of
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// random bytes that you XOR with your data. Each key is somewhat like a
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// one time pad.
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//
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// Just as you should never re-use a one time pad, you should never re-use a key.
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//
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// If you can't re-exchange a secret key before every message you could keep a
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// partial secret key and then include the other part of the key in plaintext.
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// The key would be the concatenation of the two parts of the key.
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//
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class RC4Class
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{
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public:
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RC4Class();
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//
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// Key length can be 0..256 bytes
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// Key preparation takes about 0.015 Ms on a 1Ghz PC
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//
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void Prepare_Key(const unsigned char *key_data_ptr, int key_data_len);
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//
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// In-place encryption. Call Prepare_Key first!
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// Only a few clock cycles per byte (9 or so...)
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//
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void RC4(unsigned char *buffer_ptr, int buffer_len);
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private:
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struct RC4Key
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{
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unsigned char State[256];
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unsigned char X;
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unsigned char Y;
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};
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RC4Key Key;
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};
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#endif
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