Paper 2013/767

Misuse Resistant Parallel Authenticated Encryptions

Nilanjan Datta and Mridul Nandi

Abstract

The authenticated encryptions which resist misuse of initial value (or nonce) at some desired level of privacy are two-pass or Mac-then-Encrypt constructions (inherently inefficient but provide full privacy) and online constructions, e.g., McOE, sponge-type authenticated encryptions (such as duplex, AEGIS) and COPA. Only the last one is almost parallelizable with some bottleneck in processing associated data. In this paper, {\em we design a new online secure authenticated encryption, called \tx{ELmE} or Encrypt-Linear mix-Encrypt, which is completely (two-stage) {\bf parallel} (even in associated data) and {\bf pipeline implementable}}. It also provides full privacy when associated data (which includes initial value) is not repeated. The basic idea of our construction and COPA are based on \tx{EME}, an Encrypt-Mix-Encrypt type SPRP constructions (secure against chosen plaintext and ciphertext). Unlike \tx{EME}, we consider (so does COPA) online computable {\bf linear mixing}. In addition with getting rid of bottleneck, our construction optionally supports {\bf intermediate tags} which can be verified faster with less buffer size. Intermediate tag provides security against block-wise adversaries which is meaningful in low-end device implementation.