6桁数字をMD5で総当たりしてみた

md5.scala

import java.security.MessageDigest

val md5 = MessageDigest.getInstance("MD5")

def equals[T](xs: Array[T], ys: Array[T]): Boolean = {
  if(xs.size != ys.size) return false
  var i = 0
  while(i != xs.size) {
    if(xs(i) != ys(i)) return false
    i += 1
  }
  true
}

def toBytes(x: Int): Array[Byte] = {
  var value = x
  val b = new Array[Byte](4)
  var i = 3
  while(i != 0) {
    b(i) = value.byteValue
    value = value >>> 8
    i -= 1
  }
  b(0) = value.byteValue
  b
}

def bruteForce(salt: Array[Byte], digest: Array[Byte]): List[Int] = {
  var i = 0
  val builder = List.newBuilder[Int]
  while(i != 1000000) {
    val ary = salt ++ toBytes(i)
    val di = md5.digest(ary)
    if(equals(di, digest)) builder += i
    i += 1
  }
  builder.result
}

val salt = "hoge".getBytes("UTF8")
val digest = md5.digest(salt ++ toBytes(567890))
println(bruteForce(salt, digest))

Inspired by http://qiita.com/kawasima/items/ef75f317605ce800a839 and http://z.tokumaru.org/2014/02/6php025.html

Result is 472 ms