Note: I don't feel very good about myself for having missed this one for so long, but I'm posting it in case the blindingly obvious may have escaped a few others as well.
Ever since switching to OSX, I've wondered why it didn't feature a way to do MD5 digests on files.
MD5 is a way to 'fingerprint' a file much like a hash or checksum. The MD5 algorithm is considered 'cryptographically secure' in that it produces a digest (usually represented as a string of hex digits) that is unique to a given file and is nearly impossible to duplicate by fiddling with the source file. In short, it's often used as a component in digital signature protocols and a way of verifying whether a file has been tampered with.
The built-in cksum command has an -m switch that is supposed to do just that, but appears to be broken. Of course, it would be trivial to download the sources for an external app (such as 'md5sum'), but it's always nicer to be able to do things with the tools supplied natively. Well, here it is:
openssl md5 myfileor
openssl md5 < myfileI'd completely forgotten that OSX comes standard with OpenSSL installed! Of course, it can do a LOT more than just message digests and is definitely worth investigation if you're interested in crypto.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020707014112133