Add in code for challenge 3

1 files changed, 29 insertions, 0 deletions

diff --git a/src/solvers/XorDecrypt.scala b/src/solvers/XorDecrypt.scala
new file mode 100644
index 0000000..b7f7c43
--- /dev/null
+++ b/src/solvers/XorDecrypt.scala
@@ -0,0 +1,29 @@
+package ixee.cryptopals.solvers
+
+import ixee.cryptopals.utils._
+import ixee.cryptopals.utils.ByteUtils._
+
+object XorDecrypt {
+  implicit val freq = Frequencies.cornell40kSample
+
+  def tryBestDecrypt(ciphertext: Seq[Byte]) = {
+    val key = findBestSingleByteKey(ciphertext)
+    new String((ciphertext xor Stream.continually(key)).toArray)
+  }
+
+  def findBestSingleByteKey(ciphertext: Seq[Byte]): Byte =
+    candidates(ciphertext)
+      .minBy(_._1)._2.toByte
+
+  def candidates(ciphertext: Seq[Byte]) =
+    (0 until 256)
+      .map(_.toByte)
+      .map(x => TextScorer.score(ciphertext xor Stream.continually(x)))
+      .zipWithIndex
+      .filter(_._1 != -1.0)
+
+  def candidatesAsAscii(ciphertext: Seq[Byte]) =
+    candidates(ciphertext).sortBy(_._1).map(x =>
+      new String((ciphertext xor Stream.continually(x._2.toByte)).toArray)
+    )
+}