Precomputing internal AES states in counter mode to protect keys used in AES computations

摘要

Methods, media, and systems for, in one embodiment, protecting one or more keys in an encryption and/or decryption process can use precomputed values in the process such that at least a portion of the one or more keys is not used or exposed in the process. In one example of a method, internal states of an AES encryption process are saved for use in a counter mode stream cipher operation in which the key used in the AES encryption process is not exposed or used.

主权项

1. A machine readable non-transitory storage medium containing executable program instructions which when executed by a data processing system cause the data processing system to perform a method comprising:
receiving, at a client device, a transmission of a cipher text, the cipher text having been encrypted with a key and a set of nonces using the Advanced Encryption Standard (AES) block encryption algorithm; receiving, at a client device, a transmission of a set of precomputed block cipher encryption values that were precomputed using the key and the set of nonces, wherein the set of precomputed block cipher encryption values comprise a set of internal states of the block encryption algorithm; decrypting, at the client device, the cipher text using the set of precomputed block cipher encryption values, wherein the decrypting is performed without exposing or using at least a portion of the key.