f75d43bb19
* Added AES and AES-CTR modules. AES-CTR conforms to the same counter mode used with AES in *OpenSSL*. * All algorithms now work on Big-Endian architectures. * Now uses CMake for building rather than make files and Visual Studio projects. CMake will generate whatever system is required. * Input function parameters are now marked `const` * File names have been changed to have the prefix `CryptLib_` rather than `Lib`. * Various formatting changes to the files.
129 lines
4.4 KiB
C
129 lines
4.4 KiB
C
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// CryptLib_RC4
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//
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// An implementation of RC4 stream cipher
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//
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// This is free and unencumbered software released into the public domain - June 2013 waterjuice.org
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// IMPORTS
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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#include "CryptLib_Rc4.h"
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#include <stdlib.h>
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// INTERNAL FUNCTIONS
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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#define SwapBytes( Value1, Value2 ) \
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{ \
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uint8_t temp = Value1; \
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Value1 = Value2; \
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Value2 = temp; \
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}
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// PUBLIC FUNCTIONS
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// Rc4Initialise
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//
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// Initialises an RC4 cipher and discards the specified number of first bytes.
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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void
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Rc4Initialise
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(
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Rc4Context* Context,
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void const* Key,
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uint32_t KeySize,
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uint32_t DropN
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)
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{
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uint32_t i;
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uint32_t j;
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uint32_t n;
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// Setup key schedule
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for( i=0; i<256; i++ )
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{
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Context->S[i] = (uint8_t)i;
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}
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j = 0;
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for( i=0; i<256; i++ )
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{
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j = ( j + Context->S[i] + ((uint8_t*)Key)[i % KeySize] ) % 256;
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SwapBytes( Context->S[i], Context->S[j] );
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}
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i = 0;
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j = 0;
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// Drop first bytes (if requested)
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for( n=0; n<DropN; n++ )
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{
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i = ( i + 1 ) % 256;
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j = ( j + Context->S[i] ) % 256;
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SwapBytes( Context->S[i], Context->S[j] );
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}
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Context->i = i;
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Context->j = j;
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}
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// Rc4Output
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//
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// Outputs the requested number of bytes from the RC4 stream
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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void
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Rc4Output
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(
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Rc4Context* Context,
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void* Buffer,
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uint32_t Size
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)
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{
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uint32_t n;
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for( n=0; n<Size; n++ )
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{
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Context->i = ( Context->i + 1 ) % 256;
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Context->j = ( Context->j + Context->S[Context->i] ) % 256;
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SwapBytes( Context->S[Context->i], Context->S[Context->j] );
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((uint8_t*)Buffer)[n] = Context->S[ (Context->S[Context->i] + Context->S[Context->j]) % 256 ];
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}
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}
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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// Rc4Xor
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//
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// XORs the RC4 stream with an input buffer and puts the results in an output buffer. This is used for encrypting
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// and decrypting data. InBuffer and OutBuffer can point to the same location for inplace encrypting/decrypting
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////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
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void
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Rc4Xor
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(
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Rc4Context* Context,
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void const* InBuffer,
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void* OutBuffer,
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uint32_t Size
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)
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{
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uint32_t n;
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for( n=0; n<Size; n++ )
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{
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Context->i = ( Context->i + 1 ) % 256;
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Context->j = ( Context->j + Context->S[Context->i] ) % 256;
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SwapBytes( Context->S[Context->i], Context->S[Context->j] );
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((uint8_t*)OutBuffer)[n] = ((uint8_t*)InBuffer)[n]
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^ ( Context->S[ (Context->S[Context->i] + Context->S[Context->j]) % 256 ] );
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}
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}
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