4 files changed, 19 insertions, 1 deletions
diff --git a/src/utils/ByteUtils.scala b/src/utils/ByteUtils.scala
index 18942c0..723164d 100644
--- a/src/utils/ByteUtils.scala
+++ b/src/utils/ByteUtils.scala
@@ -108,4 +108,7 @@ object ByteUtils {
 
   def hammingDistance[T : BitOps : SizedNumeric](a: Seq[T], b: Seq[T]): Int =
     (a xor b).map(_.bitsSet).reduce(_ @+ _)
+
+  def avgHammingDistance[T : BitOps : SizedNumeric](xs: Seq[Seq[T]]): Double =
+    xs.sliding(2).map({ case Stream(a: Seq[T], b: Seq[T]) => hammingDistance(a, b) }).reduce(_ @+ _) / xs.length.toDouble
 }
diff --git a/src/utils/ConversionUtils.scala b/src/utils/ConversionUtils.scala
index 95d08ce..ec3f813 100644
--- a/src/utils/ConversionUtils.scala
+++ b/src/utils/ConversionUtils.scala
@@ -5,7 +5,7 @@ import FunctionUtils._
 
 object ConversionUtils {
   def hexStr2Bytes(s: String): Seq[Byte] =
-    padToByte(s).grouped(2).map(byteStr2Byte).toSeq
+    padToByte(s).grouped(2).map(byteStr2Byte).toStream.force
 
   def byteStr2Byte(str: String): Byte =
     charSeq2Byte(str.toSeq)
diff --git a/src/utils/CryptoUtils.scala b/src/utils/CryptoUtils.scala
new file mode 100644
index 0000000..5418895
--- /dev/null
+++ b/src/utils/CryptoUtils.scala
@@ -0,0 +1,10 @@
+package ixee.cryptopals.utils
+
+object CryptoUtils {
+
+  def pkcs7pad(s: String, blockSize: Int) = {
+    val padLength = blockSize - (s.length % blockSize)
+    s + s"${padLength.toChar}" * padLength
+  }
+
+}
diff --git a/src/utils/StreamUtils.scala b/src/utils/StreamUtils.scala
index 4f803c0..be5246c 100644
--- a/src/utils/StreamUtils.scala
+++ b/src/utils/StreamUtils.scala
@@ -17,6 +17,11 @@ object StreamUtils {
   def continuous[A](xs: Seq[A]): Stream[A] =
     xs.to[Stream] append continuous(xs.to[Stream])
 
+  def pairsOf[A](xs: Seq[A]): Seq[(A, A)] =
+    (xs.init zip xs.tail.tails.toSeq) flatMap { case (elem, rest) =>
+      rest zip Stream.continually(elem)
+    }
+
 /*
   // Or just xs.to[Stream] ...
   def fromSeq[A](xs: Seq[A]): Stream[A] =