Re: keeloq decryption routine
hi
//
// Software License Agreement
//
// The software supplied herewith by Microchip Technology Incorporated
// (the "Company") for its PICmicro® Microcontroller is intended and
// supplied to you, the Company’s customer, for use solely and
// exclusively on Microchip PICmicro Microcontroller products. The
// software is owned by the Company and/or its supplier, and is
// protected under applicable copyright laws. All rights are reserved.
// Any use in violation of the foregoing restrictions may subject the
// user to criminal sanctions under applicable laws, as well as to
// civil liability for the breach of the terms and conditions of this
// license.
//
// THIS SOFTWARE IS PROVIDED IN AN "AS IS" CONDITION. NO WARRANTIES,
// WHETHER EXPRESS, IMPLIED OR STATUTORY, INCLUDING, BUT NOT LIMITED
// TO, IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE APPLY TO THIS SOFTWARE. THE COMPANY SHALL NOT,
// IN ANY CIRCUMSTANCES, BE LIABLE FOR SPECIAL, INCIDENTAL OR
// CONSEQUENTIAL DAMAGES, FOR ANY REASON WHATSOEVER.
//
//-------------------------------------------------------------------------
// LEGAL NOTICE
//
// The information contained in this document is proprietary and
// confidential information of Microchip Technology Inc. Therefore all
// parties are required to sign a non-disclosure agreement before
// receiving this document.
//-------------------------------------------------------------------------
// Keeloq Decryption Algorithm
//
// optimized for CCS PIC C compiler v. 2.535
//
// version 1.00 08/07/2000 Lucio Di Jasio
//
//=========================================================================
byte aux;
void Decrypt()
{
byte i, j, key;
sbyte p;
p = 1;
for (j=66; j>0; j--)
{
key = DKEY[p--];
if (p<0)
p+=8;
for (i=8; i>0; i--)
{
// NLF
if ( BIT_TEST( Buffer[3],6))
{
if ( !BIT_TEST( Buffer[3],1))
aux = 0b00111010; // 10
else
aux = 0b01011100; // 11
}
else
{
if ( !BIT_TEST( Buffer[3],1))
aux = 0b01110100; // 00
else
aux = 0b00101110; // 01
}
// move bit in position 7
if ( BIT_TEST( Buffer[2],3))
#asm
swapf aux,f
#endasm
if ( BIT_TEST( Buffer[1],0))
aux<<=2;
if (BIT_TEST( Buffer[0],0))
aux<<=1;
// xor with Buffer and Dkey
aux ^= Buffer[1] ^ Buffer[3] ^ key;
// shift in buffer
shift_left( Buffer, 4, BIT_TEST( aux,7));
key<<=1;
} // for i
} // for j
} // decrypt