Challenge 11

3 files changed, 61 insertions, 4 deletions

diff --git a/src/utils/crypto/CBCCipher.scala b/src/utils/crypto/CbcCipher.scala
index 227b635..28a88cd 100644
--- a/src/utils/crypto/CBCCipher.scala
+++ b/src/utils/crypto/CbcCipher.scala
@@ -7,7 +7,7 @@ import ixee.cryptopals.utils.CryptoUtils._
 import ixee.cryptopals.utils.TupleUtils._
 import ixee.cryptopals.utils.ByteUtils._
 
-class CBCCipher(private[this] val cipher: Cipher, private[this] val iv: Seq[Byte], mode: Int) extends IxeeCipher {
+class CbcCipher(private[this] val cipher: Cipher, private[this] val iv: Seq[Byte], mode: Int) extends IxeeCipher {
   val blockSize = cipher.getBlockSize
 
   var state: Seq[Byte] = iv
diff --git a/src/utils/crypto/CipherGenerator.scala b/src/utils/crypto/CipherGenerator.scala
index e7651cb..391710b 100644
--- a/src/utils/crypto/CipherGenerator.scala
+++ b/src/utils/crypto/CipherGenerator.scala
@@ -9,8 +9,16 @@ sealed trait CipherGenerator {
 
 case class EcbBuilder(primitives: SchemeBuilder) extends CipherGenerator {
   // lol
-  def encrypt = ???
-  def decrypt = ???
+  def encrypt =
+    setup(Cipher.ENCRYPT_MODE)
+  def decrypt =
+    setup(Cipher.DECRYPT_MODE)
+
+  private[this] def setup(cipherMode: Int) = {
+    val cipher = primitives.cipher
+    cipher.init(cipherMode, primitives.key)
+    new EcbCipher(cipher, cipherMode)
+  }
 }
 
 case class CbcBuilder(primitives: SchemeBuilder, iv: Seq[Byte]) extends CipherGenerator {
@@ -22,6 +30,6 @@ case class CbcBuilder(primitives: SchemeBuilder, iv: Seq[Byte]) extends CipherGe
   private[this] def setup(cipherMode: Int) = {
     val cipher = primitives.cipher
     cipher.init(cipherMode, primitives.key)
-    new CBCCipher(cipher, iv, cipherMode)
+    new CbcCipher(cipher, iv, cipherMode)
   }
 }
diff --git a/src/utils/crypto/EcbCipher.scala b/src/utils/crypto/EcbCipher.scala
new file mode 100644
index 0000000..306d5fa
--- /dev/null
+++ b/src/utils/crypto/EcbCipher.scala
@@ -0,0 +1,49 @@
+
+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 EcbCipher(private[this] val cipher: Cipher, mode: Int) extends IxeeCipher {
+  val blockSize = cipher.getBlockSize
+
+  var leftover: Seq[Byte] = Seq()
+
+  lazy val handleBlock: Seq[Byte] => Seq[Byte] =
+    if (mode == Cipher.ENCRYPT_MODE) encBlock _
+    else decBlock _
+
+  def update(data: Seq[Byte]): Seq[Byte] = {
+    val blocks = blockized(leftover ++ data).tap(updateLeftover)._1
+    blocks.foldLeft(Seq[Byte]())(_ ++ handleBlock(_))
+  }
+
+  private def decBlock(data: Seq[Byte]): Seq[Byte] =
+    cipher.update(data.toArray).toSeq
+
+  private def encBlock(data: Seq[Byte]): Seq[Byte] =
+    cipher.update(data.toArray).toSeq
+  // wouldn't hurt to invalidate this object afterward, but meh
+  // TODO: strip padding!
+  // to do it right really requires writing decryption as its own part
+  //   it's already obvious that's necessary, but to do padding stripping
+  //   properly, the last block must be withheld until an end() call is made
+  //   which is much different stateful behavior from encryption.
+  //
+  //   in cryptoUtils for now.
+  def end(): Seq[Byte] =
+    if (mode == Cipher.DECRYPT_MODE) Seq()
+    else cipher.update(pkcs7pad(leftover, blockSize).toArray)
+
+  def blockized(data: Seq[Byte]): (Seq[Seq[Byte]], Seq[Byte]) =
+    groupBlocks <-: data.splitAt(data.length - (data.length % blockSize))
+
+  def groupBlocks: Seq[Byte] => Seq[Seq[Byte]] = _.grouped(blockSize).toSeq
+
+  def updateLeftover(pair: (Seq[Seq[Byte]], Seq[Byte])) =
+    leftover = pair._2
+}