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/* Starshatter: The Open Source Project
Copyright (c) 2021-2022, Starshatter: The Open Source Project Contributors
Copyright (c) 2011-2012, Starshatter OpenSource Distribution Contributors
Copyright (c) 1997-2006, Destroyer Studios LLC.
AUTHOR: John DiCamillo
OVERVIEW
========
Simple Encryption / Decryption class
*/
#include "MemDebug.h"
#include "Encrypt.h"
// +--------------------------------------------------------------------+
void Print(const char* fmt, ...);
static long k[4] = {
0x3B398E26,
0x40C29501,
0x614D7630,
0x7F59409A
};
static void encypher(long* v)
{
DWORD y=v[0];
DWORD z=v[1];
DWORD sum=0;
DWORD delta=0x9e3779b9; // a key schedule constant
DWORD n=32; // num iterations
while (n-->0) { // basic cycle start
sum += delta;
y += (z<<4)+k[0] ^ z+sum ^ (z>>5)+k[1];
z += (y<<4)+k[2] ^ y+sum ^ (y>>5)+k[3];
}
v[0]=y;
v[1]=z;
}
static void decypher(long* v)
{
DWORD y=v[0];
DWORD z=v[1];
DWORD sum=0;
DWORD delta=0x9e3779b9; // a key schedule constant
DWORD n=32; // num iterations
sum=delta<<5;
while (n-->0) {
z-= (y<<4)+k[2] ^ y+sum ^ (y>>5)+k[3];
y-= (z<<4)+k[0] ^ z+sum ^ (z>>5)+k[1];
sum-=delta;
}
v[0]=y;
v[1]=z;
}
// +-------------------------------------------------------------------+
Text
Encryption::Encrypt(Text block)
{
int len = block.length();
if (len < 1)
return Text();
// pad to eight byte chunks
if (len & 0x7) {
len /= 8;
len *= 8;
len += 8;
}
BYTE* work = new(__FILE__,__LINE__) BYTE[len];
ZeroMemory(work, len);
CopyMemory(work, block.data(), block.length());
long* v = (long*) work;
for (int i = 0; i < len/8; i++) {
encypher(v);
v += 2;
}
Text cypher((const char*) work, len);
delete [] work;
return cypher;
}
// +-------------------------------------------------------------------+
Text
Encryption::Decrypt(Text block)
{
int len = block.length();
if (len & 0x7) {
Print("WARNING: attempt to decrypt odd length block (len=%d)\n", len);
return Text();
}
BYTE* work = new(__FILE__,__LINE__) BYTE[len];
CopyMemory(work, block.data(), len);
long* v = (long*) work;
for (int i = 0; i < len/8; i++) {
decypher(v);
v += 2;
}
Text clear((const char*) work, len);
delete [] work;
return clear;
}
// +-------------------------------------------------------------------+
static const char* codes = "abcdefghijklmnop";
Text
Encryption::Encode(Text block)
{
int len = block.length() * 2;
char* work = new(__FILE__,__LINE__) char[len + 1];
for (int i = 0; i < block.length(); i++) {
BYTE b = (BYTE) (block.data()[i]);
work[2*i] = codes[b>>4 & 0xf];
work[2*i+1] = codes[b & 0xf];
}
work[len] = 0;
Text code(work, len);
delete [] work;
return code;
}
// +-------------------------------------------------------------------+
Text
Encryption::Decode(Text block)
{
int len = block.length() / 2;
char* work = new(__FILE__,__LINE__) char[len + 1];
for (int i = 0; i < len; i++) {
char u = block[2*i];
char l = block[2*i + 1];
work[i] = (u - codes[0]) << 4 |
(l - codes[0]);
}
work[len] = 0;
Text clear(work, len);
delete [] work;
return clear;
}
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