Cryptography is the science of keeping data secure through the use of computer algorithms; for example, by encrypting data so that it cannot be read by eavesdroppers as it is transmitted or by producing a message authentication codes for data that can be used to detect when an unauthorised entity attempts to change it. Cryptography has a huge presence in our daily lives: it exists in our mobile phones, in our web browsers, and in our banking systems. The biggest problem in cryptography is one of trust: how can we be sure that an algorithm does the job that it is designed to do? How can we be sure that some clever attacker hasn't worked out a way to undo an encryption or create new message authentication codes for altered data?

One solution is to use the provable security - a technique which models the attacker's capabilities and objectives, and gives a mathematical proof that the attacker cannot break the system. However, provable security has intrinsic weaknesses and some respected researchers have recently argued that the techniques do more harm than good from an engineering point of view. In this seminar we will give a brief introduction to cryptography and provable security, and discuss some of the arguments for and against its use in academia and industry.