Descent3/netgames/dmfc/encryption.cpp

/*
* $Logfile: /DescentIII/Main/dmfc/encryption.cpp $
* $Revision: 1.1.1.1 $
* $Date: 2003/08/26 03:57:21 $
* $Author: kevinb $
*
* header file for ICE encryption class
*
* $Log: encryption.cpp,v $
* Revision 1.1.1.1  2003/08/26 03:57:21  kevinb
* initial 1.5 import
*
 * 
 * 2     7/08/99 2:37a Jeff
 * created encryption class based off of ICE encryption
*
* $NoKeywords: $
*/

#include "encryption.h"

class IceSubkey 
{
public:
	unsigned long val[3];
};

// the S-boxes
static unsigned long ice_sbox[4][1024];
static int ice_sboxes_initialised = 0;

// modulo values for the S-boxes
static const int ice_smod[4][4] = 
{
	{333, 313, 505, 369},
	{379, 375, 319, 391},
	{361, 445, 451, 397},
	{397, 425, 395, 505}
};

// XOR values for the S-boxes
static const int ice_sxor[4][4] = 
{
	{0x83, 0x85, 0x9b, 0xcd},
	{0xcc, 0xa7, 0xad, 0x41},
	{0x4b, 0x2e, 0xd4, 0x33},
	{0xea, 0xcb, 0x2e, 0x04}
};

// Permutation values for the P-box
static const unsigned long	ice_pbox[32] = 
{
	0x00000001, 0x00000080, 0x00000400, 0x00002000,
	0x00080000, 0x00200000, 0x01000000, 0x40000000,
	0x00000008, 0x00000020, 0x00000100, 0x00004000,
	0x00010000, 0x00800000, 0x04000000, 0x20000000,
	0x00000004, 0x00000010, 0x00000200, 0x00008000,
	0x00020000, 0x00400000, 0x08000000, 0x10000000,
	0x00000002, 0x00000040, 0x00000800, 0x00001000,
	0x00040000, 0x00100000, 0x02000000, 0x80000000
};

// key rotation schedule
static const int ice_keyrot[16] = 
{
	0, 1, 2, 3, 2, 1, 3, 0,
	1, 3, 2, 0, 3, 1, 0, 2
};

//
// 8-bit Galois Field multiplication of a by b, modulo m.
// Just like arithmetic multiplication, except that additions and
// subtractions are replaced by XOR.
//
static uint gf_mult(uint a,uint	b,uint m) 
{
	uint res = 0;

	while(b)
	{
		if(b&1)
			res ^= a;

		a <<= 1;
	    b >>= 1;

	    if(a>=256)
			a ^= m;
	}

	return (res);
}

//
// Galois Field exponentiation.
// Raise the base to the power of 7, modulo m.
//
static unsigned long gf_exp7(uint b, uint m)
{
	uint x;

	if(b==0)
		return 0;

	x = gf_mult (b, b, m);
	x = gf_mult (b, x, m);
	x = gf_mult (x, x, m);

	return (gf_mult (b, x, m));
}

//
// Carry out the ICE 32-bit P-box permutation.
//
static unsigned long ice_perm32 (unsigned long x)
{
	unsigned long res = 0;
	const unsigned long	*pbox = ice_pbox;

	while(x)
	{
		if(x&1)
			res |= *pbox;
	    pbox++;
	    x >>= 1;
	}

	return (res);
}

//
// Initialise the ICE S-boxes.
// This only has to be done once.
//
static void ice_sboxes_init(void)
{
	int	i;

	for(i=0;i<1024;i++)
	{
		int col=(i>>1)&0xff;
	    int	row=(i&0x1)|((i&0x200)>>8);
	    unsigned long x;

	    x = gf_exp7(col^ice_sxor[0][row],ice_smod[0][row])<<24;
	    ice_sbox[0][i] = ice_perm32 (x);

	    x = gf_exp7(col^ice_sxor[1][row],ice_smod[1][row])<<16;
	    ice_sbox[1][i] = ice_perm32 (x);

	    x = gf_exp7(col^ice_sxor[2][row],ice_smod[2][row])<<8;
	    ice_sbox[2][i] = ice_perm32 (x);

	    x = gf_exp7(col^ice_sxor[3][row],ice_smod[3][row]);
	    ice_sbox[3][i] = ice_perm32 (x);
	}
}

//
// Create a new ICE key.
//
IceKey::IceKey(int n)
{
	if(!ice_sboxes_initialised) 
	{
	    ice_sboxes_init();
	    ice_sboxes_initialised = 1;
	}

	if(n<1)
	{
		_size = 1;
	    _rounds = 8;
	}else{
		_size = n;
	    _rounds = n*16;
	}

	_keysched = new IceSubkey[_rounds];
}

//
// Destroy an ICE key.
//
IceKey::~IceKey ()
{
	int	i, j;

	for(i=0;i<_rounds;i++)
	{
		for(j=0;j<3;j++)
		{
			_keysched[i].val[j] = 0;
		}
	}

	_rounds = _size = 0;

	delete[] _keysched;
}

//
// The single round ICE f function.
//
static unsigned long ice_f(unsigned long p,const IceSubkey *sk)
{
	unsigned long tl, tr;		/* Expanded 40-bit values */
	unsigned long al, ar;		/* Salted expanded 40-bit values */

	// Left half expansion
	tl = ((p >> 16) & 0x3ff) | (((p >> 14) | (p << 18)) & 0xffc00);

	// Right half expansion
	tr = (p & 0x3ff) | ((p << 2) & 0xffc00);

	// Perform the salt permutation
	al = sk->val[2] & (tl ^ tr);
	ar = al ^ tr;
	al ^= tl;

	al ^= sk->val[0];		// XOR with the subkey
	ar ^= sk->val[1];

	// S-box lookup and permutation
	return (ice_sbox[0][al>>10] | ice_sbox[1][al & 0x3ff]	|
			ice_sbox[2][ar>>10] | ice_sbox[3][ar & 0x3ff]);
}

//
// Encrypt a block of 8 bytes of data with the given ICE key.
//
void IceKey::encrypt(const ubyte *ptext,ubyte *ctext) const
{
	int i;
	unsigned long l,r;

	l = (((unsigned long) ptext[0]) << 24)	|
		(((unsigned long) ptext[1]) << 16)	|
		(((unsigned long) ptext[2]) << 8)	| ptext[3];

	r = (((unsigned long) ptext[4]) << 24)	| 
		(((unsigned long) ptext[5]) << 16)	| 
		(((unsigned long) ptext[6]) << 8)	| ptext[7];

	for(i=0;i<_rounds;i+=2) 
	{
		l ^= ice_f(r,&_keysched[i]);
	    r ^= ice_f(l,&_keysched[i+1]);
	}

	for(i=0;i<4;i++)
	{
		ctext[3 - i] = (ubyte)r&0xff;
	    ctext[7 - i] = (ubyte)l&0xff;

		r >>= 8;
	    l >>= 8;
	}
}

//
// Decrypt a block of 8 bytes of data with the given ICE key.
//
void IceKey::decrypt(const ubyte *ctext,ubyte *ptext) const
{
	int i;
	unsigned long l,r;

	l = (((unsigned long) ctext[0]) << 24)	|
		(((unsigned long) ctext[1]) << 16)	|
		(((unsigned long) ctext[2]) << 8)	| ctext[3];
	r = (((unsigned long) ctext[4]) << 24)	| 
		(((unsigned long) ctext[5]) << 16)	| 
		(((unsigned long) ctext[6]) << 8)	| ctext[7];

	for(i=_rounds-1;i>0;i-=2) 
	{
	    l ^= ice_f(r,&_keysched[i]);
	    r ^= ice_f(l,&_keysched[i-1]);
	}

	for(i=0;i<4;i++) 
	{
	    ptext[3 - i] = (ubyte)r&0xff;
	    ptext[7 - i] = (ubyte)l&0xff;

	    r >>= 8;
	    l >>= 8;
	}
}

//
// Set 8 rounds [n, n+7] of the key schedule of an ICE key.
//
void IceKey::scheduleBuild(unsigned short *kb,int n,const int *keyrot)
{
	int	i;

	for(i=0;i<8;i++)
	{
		int	j;
		int	kr = keyrot[i];
	    IceSubkey *isk = &_keysched[n+i];

	    for(j=0;j<3;j++)
			isk->val[j] = 0;

	    for(j=0;j<15;j++)
		{
			int	k;
			unsigned long *curr_sk = &isk->val[j%3];

			for(k=0;k<4;k++)
			{
				ushort *curr_kb = &kb[(kr+k)&3];
				int	bit = *curr_kb&1;

				*curr_sk = (*curr_sk<<1)|bit;
				*curr_kb = (*curr_kb>>1)|((bit^1)<<15);
			}
	    }
	}
}

//
// Set the key schedule of an ICE key.
//
void IceKey::set(const ubyte *key)
{
	int i;

	if(_rounds==8)
	{
		ushort kb[4];

	    for(i=0;i<4;i++)
		{
			kb[3-i] = (key[i*2]<<8)|key[i*2+1];
		}

		scheduleBuild(kb,0,ice_keyrot);
	    return;
	}

	for(i=0;i<_size;i++)
	{
		int j;
	    ushort kb[4];

	    for(j=0;j<4;j++)
		{
			kb[3-j] = (key[i*8+j*2]<<8)|key[i*8+j*2+1];

			scheduleBuild(kb,i*8,ice_keyrot);
			scheduleBuild(kb,_rounds-8-i*8,&ice_keyrot[8]);
		}
	}
}

//
// Return the key size, in bytes.
//
int IceKey::keySize(void) const
{
	return (_size*8);
}

//
// Return the block size, in bytes.
//
int IceKey::blockSize(void) const
{
	return 8;
}