clean up extra crypto a bit

extra/crypto/barrett/barrett.factor

@@ -8,5 +8,3 @@ IN: crypto.barrett
     #! size = word size in bits (8, 16, 32, 64, ...)
     [ [ log2 1+ ] [ / 2 * ] bi* ]
     [ 2^ rot ^ swap /i ] 2bi ;
-
-

extra/crypto/hmac/hmac.factor

@@ -1,3 +1,5 @@
+! Copyright (C) 2008 Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
 USING: arrays combinators checksums checksums.md5
 checksums.sha1 checksums.md5.private io io.binary io.files
 io.streams.byte-array kernel math math.vectors memoize sequences

extra/crypto/timing/timing.factor

@@ -1,3 +1,5 @@
+! Copyright (C) 2008 Doug Coleman.
+! See http://factorcode.org/license.txt for BSD license.
 USING: kernel math threads system calendar ;
 IN: crypto.timing
 

extra/crypto/xor/xor.factor

@@ -8,5 +8,5 @@ IN: crypto.xor
 ERROR: empty-xor-key ;
 
 : xor-crypt ( seq key -- seq' )
-    dup empty? [ empty-xor-key ] when
+    [ empty-xor-key ] when-empty
     [ dup length ] dip '[ _ mod-nth bitxor ] 2map ;