Paper 2004/125

EME*: extending EME to handle arbitrary-length messages with associated data

Shai Halevi

Abstract

This work describes a mode of operation, EME*, that turns a regular block cipher into a length-preserving enciphering scheme for messages of (almost) arbitrary length. Specifically, the resulting scheme can handle any bit-length, not shorter than the block size of the underlying cipher, and it also handles associated data of arbitrary bit-length. Such a scheme can either be used directly in applications that need encryption but cannot afford length expansion, or serve as a convenient building block for higher-level modes. The mode EME* is a refinement of the EME mode of Halevi and Rogaway, and it inherits the efficiency and parallelism from the original EME.