commit 544db619f024d8624368281b15b6b147a483175b
Author: Thomas Hintz <t@thintz.com>
Date:   Sat Apr 16 18:51:01 2011 -0400

    First commit.

diff --git a/hmac.scm b/hmac.scm
new file mode 100644
index 0000000..c884d16
--- /dev/null
+++ b/hmac.scm
@@ -0,0 +1,11 @@
+(use sha1 srfi-4 srfi-4-utils)
+
+; taken from example at http://wiki.call-cc.org/drupal-xml-rpc
+(define (sha1-hmac key)
+  (when (> (string-length key) 64) (set! key (sha1-binary-digest key)))
+  (set! key (string-pad-right key 64 (integer->char 0)))
+  (set! key (blob->u8vector (string->blob key)))
+  (let ((ipad (blob->string (u8vector->blob (u8vector-map (lambda (v) (bitwise-xor v #x36)) key))))
+        (opad (blob->string (u8vector->blob (u8vector-map (lambda (v) (bitwise-xor v #x5c)) key)))))
+    (lambda (message)
+      (sha1-binary-digest (string-append opad (sha1-binary-digest (string-append ipad message)))))))
\ No newline at end of file