From http://www.jwz.org/xscreensaver/xscreensaver-5.24.tar.gz

[xscreensaver] / OSX / sign_update.rb

diff --git a/OSX/sign_update.rb b/OSX/sign_update.rb
new file mode 100755 (executable)
index 0000000..6d03e2e
--- /dev/null
+++ b/OSX/sign_update.rb
@@ -0,0 +1,7 @@
+#!/usr/bin/ruby
+if ARGV.length < 2
+  puts "Usage: ruby sign_update.rb update_archive private_key"
+  exit
+end
+
+puts `openssl dgst -sha1 -binary < "#{ARGV[0]}" | openssl dgst -dss1 -sign "#{ARGV[1]}" | openssl enc -base64`
\ No newline at end of file