src/utils/crypto/CBCDecrypter.scala


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package ixee.cryptopals.utils.crypto

import javax.crypto.Cipher
import ixee.cryptopals.utils.ConversionUtils._
import ixee.cryptopals.utils.FunctionUtils._
import ixee.cryptopals.utils.CryptoUtils._
import ixee.cryptopals.utils.TupleUtils._
import ixee.cryptopals.utils.ByteUtils._

class CBCDecrypter(cipher: Cipher, init: Seq[Byte]) {
  val blockSize = 16

  var state: Seq[Byte] = init
  var leftover: Seq[Byte] = Seq()

  def dec(data: Seq[Byte]): Seq[Byte] = {
    val (blocks, newLeftover) = blockized(leftover ++ data)(blockSize)
    leftover = newLeftover
    blocks.map(decBlock _).foldLeft(Seq[Byte]())(_ ++ _)
  }

  def decBlock(data: Seq[Byte]): Seq[Byte] = {
    val ret = cipher.update(data.toArray).toSeq xor state
    state = data
    ret
  }

  def end(): Seq[Byte] =
    cipher.doFinal((pkcs7pad(leftover, blockSize) xor state).toArray)

  def blockized(data: Seq[Byte])(size: Int): (Seq[Seq[Byte]], Seq[Byte]) =
    groupBlocks <-: data.splitAt(data.length - (data.length % size))

  def groupBlocks: Seq[Byte] => Seq[Seq[Byte]] = _.grouped(blockSize).toSeq
}