ARCFour.scala

class ARCFour{
  private var x:Int = _
  private var y:Int = _
  private val state = new Array[Int](256)

  def decrypt(src:Array[Byte], off:Int, length:Int):Array[Byte]={
    encrypt(src, off, length)
  }

  def decrypt(src:Array[Byte], soff:Int,
              dst:Array[Byte], doff:Int, length:Int){
    encrypt(src, soff, dst, doff, length)
  }

  def encrypt(src:Array[Byte], off:Int, length:Int):Array[Byte]={
    val dst = new Array[Byte](length)
    encrypt(src, off, dst , 0, length)
    dst
  }

  def encrypt(src:Array[Byte], soff:Int,
              dst:Array[Byte], doff:Int, length:Int){
    var sx, sy=0
    var i = 0
    while(i < length){
      x = (x+1)&0xff
      sx = state(x)
      y = (y+sx)&0xff
      sy = state(y)
      state(y) = sx
      state(x) = sy
      dst(i+doff) = ((src(i+soff)&0xff)^(state((sx+sy)&0xff))).asInstanceOf[Byte]
      i += 1
    }
  }

  def init(key:Array[Byte]){
    x=0
    y=0
    (state /: (0 until 256)){(b, i) => b(i)=i; b}
    val keylen = key.length
    var kindex, sindex = 0
    var i = 0
    while(i < state.length){
      sindex = (sindex+(key(kindex)&0xff)+state(i))&0xff
      state(i) = state(sindex) match {
        case u => state(sindex) = state(i); u
      }
      i += 1
      kindex += 1
      if(kindex >= keylen){
        kindex = 0
      }
    }
  }
}