Characterization of EME with Linear Mixing

Abstract

Abstract. Encrypt-Mix-Encrypt is a type of SPRP based construction, where a masked plaintext is encrypted in ECB mode of, then a non-linear mixing is performed and then again an encryption is performed in ECB mode which is masked to produce the ciphertext. Using the property of the binary field, the authors proved that the construction is not SPRP secure if the mixing used is linear. In this paper, we observe that relaxing the mixing operation to some specific efficient linear mixing provides the PRP property of the construction. Moreover choosing a linear mixing that gives the online property is not a difficult task. We can use this fact to construct an efficient Online PRP using Encrypt-Mix-Encrypt type of construction with the mix operation being a linear online mixing, making the construction efficient and online. We also show that the construction with linear mixing doesn't provide SPRP security even if we perform all the operations in a prime field instead of binary field. Thus, we fully characterize EME with linear mixing.

Pipelineable On-line Encryption

“…Moreover, we illustrate in Appendix B that EME-based designs lose the OPRP-CCA-security in the decryption-misuse setting, which disqualifies COPA and ELmE for the OTN application scenario. More generally, Datta and Nandi [16] showed recently that EME constructions with linear mixing can not provide IND-CCA-security. Therefore, POET represents the first non-sequential OAE scheme with resistance against both nonce and decryption misuse.…”