Combination white box/black box cryptographic processes and apparatus

Abstract

Method and apparatus for increasing security of a cryptographic algorithm such as deciphering, enciphering, or a digital signature. A cryptographic algorithm and a key are provided such that a deciphering process, for instance, is partitioned between two portions. The portion of the cryptographic algorithm carried out in the first portion is implemented in a 'white box' model such that it is highly secure even against an attack by the user who has full access to internal operations, code execution and memory of the user device, such as a hacker or attacker. The remaining portion of the algorithm is carried out in the second portion. Since this second portion has relaxed security constraints, its code may be implemented using a 'black box' approach where its code execution may be more efficient and faster, not requiring the code obfuscation of the white box implementation in the user device. This partitioning may be achieved using a delegation protocol. The chief advantage is that even given a limited code size for the cryptographic process, the security of the system is improved by carrying out the more computationally intensive functions more efficiently in the black box portion and executing the less computationally intensive function in the white box portion.