[Cryptography] On the deployment of client-side certs

[Pieter Rogaar]

> That's within practically everybody's capability, (in the sense that
> code to create self-signed certs is all over the place and most SSL
> implementations allow certs to be used on both sides) but nobody's about
> to do it (consumers) or require it to be done (bankers, merchants, etc)
> or facilitate doing it (servers, browsers, mail clients, etc).

In today's threat models, there is also the metadata angle to consider. 
Client certificates are exchanged before the TLS connection is encrypted. 
Therefore, any information in the client certificate is sent in the clear. 
For server-to-server, this may be acceptable, but for regular clients: no. 
In this sense, client certificates are a definite step back from the 
web-based authentication to which we have become accustomed.

Pieter