A comparison of certificate validation methods for use in a web environment

So, GSM (Groupe Spécial Mobile) is the most widely-used standard for cellular communication. Wikipedia tells me that 80% of the cellular market uses this standard, representing about 4.3 billion people. And guess what? The encryption algorithm of this standard is completely broken-- according to this paper, anyway. And the *way* in which the paper goes about breaking the algorithm is itself beautiful, illustrating a number of common crypto flaws simultaneously.