Cryptographic Innuendos
Neil Madden recently wrote a blog post titled, Digital Signatures and How to Avoid Them. One of the major points he raised is:
Another way that signatures cause issues is that they are too powerful for the job they are used for. You just wanted to authenticate that an email came from a legitimate server, but now you are providing irrefutable proof of the provenance of leaked private communications. Oops!
Signatures are very much the hammer of cryptographic primitives. As well as authenticating a message, they also provide third-party verifiability and (part of) non-repudiation.
Later, he goes on to make recommendations for alternatives. Namely HMAC, possibly with a KEM. His recommendations are sensible and straightforward.
Even if there’s no immediately obvious fatal flaw in this design, it’s always possible that I screwed something up.
