A System using Provably Strong Cryptography is Probably not Secure: Some Practical Attacks

Abstract

Strong cryptography Is necessary for achieving the defined system security goals, but definitely not sufficient to guarantee that the security goal Is achieved by the system. A number of modern day systems claim to incorporate security mechanisms based on cryptographic algorithms that are provably secure. Strong cryptography can ensure that a system can withstand targeted mathematical attacks on cryptographic algorithms up to a point-the point at which it becomes easier to get the information some other way. Systems incorporating strong cryptography have been compromised by attacks that have rarely broken the cryptographic algorithm itself. Ingenious “side” channels have often been used to violate the security goal. This is because non-cryptographic parts of systems are much easier to break. Flaws can be anywhere: the threat model, the system design, the software or hardware Implementation, the system management. Security is a chain, and a single weak link can break the entire system. Fatal bugs may be far removed from the security portion of the software; a design decision that has nothing to do with security can nonetheless create a security flaw.

This paper aims at illustrating some practical attacks that have been reported in the recent past and have led to compromise of systems that have contained mathematically provable strong cryptographic algorithms.