diff --git a/cryptopals.lisp b/cryptopals.lisp
index af0a66e..0662587 100644
--- a/cryptopals.lisp
+++ b/cryptopals.lisp
@@ -1,7 +1,12 @@
 (ql:quickload :cl-base64)
 (ql:quickload :iterate)
+(ql:quickload :fiveam)
 
 (use-package :iterate)
+(use-package :fiveam)
+
+(def-suite cryptopals)
+(in-suite cryptopals)
 
 (defun hex-to-dec (hex-chr)
   (cond
@@ -12,6 +17,11 @@
     ((char<= #\A hex-chr #\F)
      (+ (- (char-code hex-chr) (char-code #\A)) 10))))
 
+(defun dec-to-hex (dec-chr)
+  (cond
+    ((<= 0 dec-chr 9) (code-char (+ (char-code #\0) dec-chr)))
+    ((<= 10 dec-chr 15) (code-char (+ (char-code #\a) (- dec-chr 10))))))
+
 (defun hex-to-bytes (hex-str)
   (iter
     (for i below (length hex-str) by 2)
@@ -19,8 +29,33 @@
           (c2 (hex-to-dec (aref hex-str (1+ i)))))
         (collect (+ (* 16 c1) c2) result-type (vector (unsigned-byte 8)))))) 
 
+(defun bytes-to-hex (bytes)
+  (iter
+    (for i in-vector bytes)
+    (collect (dec-to-hex (ash (logand i #xff) -4)) result-type string)
+    (collect (dec-to-hex (logand i #xf)) result-type string)))
+
 ;; set 1 challenge 1
 (defun hex-to-base64 (hex-str)
   (cl-base64:usb8-array-to-base64-string (hex-to-bytes hex-str)))
 
+(test s1c1
+  (let ((in "49276d206b696c6c696e6720796f757220627261696e206c696b65206120706f69736f6e6f7573206d757368726f6f6d")
+        (out "SSdtIGtpbGxpbmcgeW91ciBicmFpbiBsaWtlIGEgcG9pc29ub3VzIG11c2hyb29t"))
+    (is (string= (hex-to-base64 in) out))))
 
+;; set 1 challenge 2
+(defun fixed-xor (s1 s2)
+  (bytes-to-hex 
+    (iter
+      (for x in-vector (hex-to-bytes s1))
+      (for y in-vector (hex-to-bytes s2))
+      (collect (logxor x y) result-type (vector (unsigned-byte 8))))))
+
+(test s1c2
+  (let ((in1 "1c0111001f010100061a024b53535009181c")
+        (in2 "686974207468652062756c6c277320657965")
+        (out "746865206b696420646f6e277420706c6179"))
+    (is (string= (fixed-xor in1 in2) out))))
+
+(run! 'cryptopals)