php mcrypt_generic_init,PHP: mcrypt_generic_init - Manual

The mcrypt implementation of RC2 algorithm supports an effective key length of 1024 bits only.

It is however possible to use an effective key length in 1..1024 bits, by transforming the key before use as follows:

{$pitable= array(0xD9,0x78,0xF9,0xC4,0x19,0xDD,0xB5,0xED,0x28,0xE9,0xFD,0x79,0x4A,0xA0,0xD8,0x9D,0xC6,0x7E,0x37,0x83,0x2B,0x76,0x53,0x8E,0x62,0x4C,0x64,0x88,0x44,0x8B,0xFB,0xA2,0x17,0x9A,0x59,0xF5,0x87,0xB3,0x4F,0x13,0x61,0x45,0x6D,0x8D,0x09,0x81,0x7D,0x32,0xBD,0x8F,0x40,0xEB,0x86,0xB7,0x7B,0x0B,0xF0,0x95,0x21,0x22,0x5C,0x6B,0x4E,0x82,0x54,0xD6,0x65,0x93,0xCE,0x60,0xB2,0x1C,0x73,0x56,0xC0,0x14,0xA7,0x8C,0xF1,0xDC,0x12,0x75,0xCA,0x1F,0x3B,0xBE,0xE4,0xD1,0x42,0x3D,0xD4,0x30,0xA3,0x3C,0xB6,0x26,0x6F,0xBF,0x0E,0xDA,0x46,0x69,0x07,0x57,0x27,0xF2,0x1D,0x9B,0xBC,0x94,0x43,0x03,0xF8,0x11,0xC7,0xF6,0x90,0xEF,0x3E,0xE7,0x06,0xC3,0xD5,0x2F,0xC8,0x66,0x1E,0xD7,0x08,0xE8,0xEA,0xDE,0x80,0x52,0xEE,0xF7,0x84,0xAA,0x72,0xAC,0x35,0x4D,0x6A,0x2A,0x96,0x1A,0xD2,0x71,0x5A,0x15,0x49,0x74,0x4B,0x9F,0xD0,0x5E,0x04,0x18,0xA4,0xEC,0xC2,0xE0,0x41,0x6E,0x0F,0x51,0xCB,0xCC,0x24,0x91,0xAF,0x50,0xA1,0xF4,0x70,0x39,0x99,0x7C,0x3A,0x85,0x23,0xB8,0xB4,0x7A,0xFC,0x02,0x36,0x5B,0x25,0x55,0x97,0x31,0x2D,0x5D,0xFA,0x98,0xE3,0x8A,0x92,0xAE,0x05,0xDF,0x29,0x10,0x67,0x6C,0xBA,0xC9,0xD3,0x00,0xE6,0xCF,0xE1,0x9E,0xA8,0x2C,0x63,0x16,0x01,0x3F,0x58,0xE2,0x89,0xA9,0x0D,0x38,0x34,0x1B,0xAB,0x33,0xFF,0xB0,0xBB,0x48,0x0C,0x5F,0xB9,0xB1,0xCD,0x2E,0xC5,0xF3,0xDB,0x47,0xE5,0xA5,0x9C,0x77,0x0A,0xA6,0x20,0x68,0xFE,0x7F,0xC1,0xAD);$invpitable=array_flip($pitable);//    Apply the regular RC2 key expansion algorithm.$t=strlen($key);$key=array_values(unpack('C*C',$key));

for ($i=$t;$i<128;$i++)$key[$i] =$pitable[($key[$i-1] +$key[$i-$t]) &0xFF];$t8= ($effKeyLen+7) >>3;$tm=0xFF>> (8*$t8-$effKeyLen);$i=128-$t8;$key[$i] =$pitable[$key[$i] &$tm];

while ($i--)$key[$i] =$pitable[$key[$i+1] ^$key[$i+$t8]];//    Map the first byte: this operation will be undone by

//        mcrypt internals.$key[0] =$invpitable[$key[0]];//    Return the transformed key as a string.array_unshift($key,'C*');

returncall_user_func_array('pack',$key);

}//    Usage example$r=mcrypt_module_open(MCRYPT_RC2,$algoDir,$mode,$modeDir);mcrypt_generic_init($r,transformKey($originalKey,$effectiveKeyLength),$iv);?>