XTEA

This ia an implementation of the  XTEA cypher.

Code

const DELTA = 0x9E3779B9;
const ROUNDS = 32;

static final function encipher(out int v[2], int k[4])
{
    local int y, z, sum, n;

    y=v[0]; z=v[1]; sum=0; n=0;

    while(n++ < ROUNDS)
    {
        y += (z << 4 ^ z >>> 5) + z ^ sum + k[sum&3];
        sum += DELTA;
        z += (y << 4 ^ y >>> 5) + y ^ sum + k[sum>>>11 & 3];
    }

    v[0]=y; v[1]=z;
}

static final function decipher(out int v[2], int k[4])
{
    local int y, z, sum, n;

    y=v[0]; z=v[1]; sum=DELTA*ROUNDS; n=0;

    while(n++ < ROUNDS)
    {
        z -= (y << 4 ^ y >>> 5) + y ^ sum + k[sum>>>11 & 3];
        sum -= DELTA;
        y -= (z << 4 ^ z >>> 5) + z ^ sum + k[sum&3];
    }
   
    v[0]=y; v[1]=z;
}


static final function buildkey(string key, out int k[4])
{
    local int i;

    for (i = 0; i < 4; i++)
    {
        k[i] = (asc(mid(key, i*4, 1)) << 24) | ((asc(mid(key, i*4+1, 1)) & 0xff) << 16) | ((asc(mid(key, i*4+2, 1)) & 0xff) << 8) | (asc(mid(key, i*4+3, 1)) & 0xff);
    }
}

static function string encrypt(string str, string key)
{
    local int i, v[2], k[4]; 
    local string ret;

    buildkey(key, k);

    while (i < len(str))
    {
        v[0] = (asc(mid(str, i++, 1)) << 24) | ((asc(mid(str, i++, 1))&0xff) << 16) | ((asc(mid(str, i++, 1))&0xff) << 8) | (asc(mid(str, i++, 1))&0xff);
        v[1] = (asc(mid(str, i++, 1)) << 24) | ((asc(mid(str, i++, 1))&0xff) << 16) | ((asc(mid(str, i++, 1))&0xff) << 8) | (asc(mid(str, i++, 1))&0xff);

        encipher(v, k);

        ret = ret $ DecToHex(v[0], 4) $ DecToHex(v[1], 4);

        v[0] = 0; v[1] = 0;
    }

    return ret;
}

static function string decrypt(string str, string key)
{
    local int i, v[2], k[4]; 
    local string ret;

    buildkey(key, k);
    
    while (i < len(str))
    {
        v[0] = HexToDec(Mid(str, i, 8));
        i+=8;
        v[1] = HexToDec(Mid(str, i, 8));
        i+=8;

        decipher(v, k);

        ret = ret $ Chr((v[0] >>> 24) & 0xff) $ Chr((v[0] >>> 16) & 0xff) $ Chr((v[0] >>> 8) & 0xff) $ Chr(v[0] & 0xff);
        ret = ret $ Chr((v[1] >>> 24) & 0xff) $ Chr((v[1] >>> 16) & 0xff) $ Chr((v[1] >>> 8) & 0xff) $ Chr(v[1] & 0xff);

        v[0] = 0; v[1] = 0;
    }

    return ret;
}

static final function int HexToDec(string hexcode) // Borrowed from ElMuerte's LibHTTP
{
    local int res, i, cur;

    res = 0;
    hexcode = Caps(hexcode);
    for (i = 0; i < len(hexcode); i++)
    {
        cur = Asc(Mid(hexcode, i, 1));
        if (cur == 32) return res;
        cur -= 48; // 0 = ascii 30
        if (cur > 9) cur -= 7;
        if ((cur > 15) || (cur < 0)) return -1; // not possible
        res = res << 4;
        res += cur;
    }
    return res;
}


static final function string DecToHex(int dec, int size)
{
    const hex = "0123456789ABCDEF";
    local string s;
    local int i;

    for (i = 0; i < size*2; i++)
    {
        s = mid(hex, dec & 0xf, 1) $ s;
        dec = dec >>> 4;
    }

    return s;
}

Usage

To encrypt a message use:

EncryptedMessage = encrypt(Message, Key)

To decrypt a message use:

Message = decrypt(EncryptedMessage, Key)

License

Copyright 2004 (c) Petr Jelinek

Released under the LesserOpenUnrealModLicense

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Category Algorithm