对OCB模式的冲突攻击

Collision Attacks on OCB

OCB模式是可并行处理的分组加密模式,在加密的同时还提供了鉴别服务.速度快是OCB模式的一个重要特点,但这也导致了其安全隐患问题。文章给出了一种新的对OCB模式的攻击方法,当某种冲突发生时,很容易对OCB模式进行攻击,使其完全丧失鉴别的能力。这种攻击的限制条件很少,攻击范围很大,而且容易实现.因此,为了保证OCB模式鉴别上的安全,必须限制其单个密钥下处理的数据量,从而限制了OCB模式的应用范围.

OCB is a parallelizable block-cipher mode of operation that simultaneously provides privacy and authenticity. High-speed is one of the most important advantages.But it also leads to the problems on security.In this paper,a new attack scheme on OCB is given out.When a collision occurs attacks are quite effective on the OCB block cipher mode. OCB loses its authentication capability to keep adequate authentication security.The scheme is easy to be achieved with little limitation.And it can threaten almost the whole message.So OCB has to be limited in the amount of data it processes.This restriction casts doubt on the wisdom of using OCB.