challenge: do challenge 2

* challenge/c02.go: Challenge 2 snafu.
* cryptopals.go: Add challenge 2.
* enc/hex.go (DecToHexChar): New function.
* enc/xor.go  (FixedXOR): New function.

1 files changed, 2 insertions, 0 deletions

diff --git a/cryptopals.go b/cryptopals.go
index 9c1c803..37580be 100644
--- a/cryptopals.go
+++ b/cryptopals.go
@@ -20,5 +20,7 @@ func main() {
 		flag.PrintDefaults()
 	case 1:
 		challenge.C1()
+	case 2:
+		challenge.C2()
 	}
 }