1 files changed, 36 insertions, 0 deletions
diff --git a/src/utils/crypto/CBCDecrypter.scala b/src/utils/crypto/CBCDecrypter.scala
new file mode 100644
index 0000000..a6cf855
--- /dev/null
+++ b/src/utils/crypto/CBCDecrypter.scala
@@ -0,0 +1,36 @@
+
+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
+}