SAEB: A Lightweight Blockcipher-Based AEAD Mode of Operation

Abstract

Lightweight cryptography in computationally constrained devices is actively studied. In contrast to advances of lightweight blockcipher in the last decade, lightweight mode of operation is seemingly not so mature, yet it has large impact in performance. Therefore, there is a great demand for lightweight mode of operation, especially that for authenticated encryption with associated data (AEAD). Among many known properties of conventional modes of operation, the following four properties are essential for constrained devices:

1. Minimum State Size: the state size equals to a block size of a blockcipher.
2. Inverse Free: no need for a blockcipher decryption.
3. XOR Only: only XOR is needed in addition to a blockcipher encryption.
4. Online: a data block is processed only once.

The properties 1 and 4 contribute to small memory usage, and the properties 2 and 3 contribute to small program/circuit footprint. On top of the above properties, the fifth property regarding associated data (AD) is also important for performance:

1. Efficient Handling of Static AD: static AD can be precomputed.

We design a lightweight blockcipher-based AEAD mode of operation called SAEB: the first mode of operation that satisfies all the five properties to the best of our knowledge. Performance of SAEB is evaluated in various software and hardware platforms. The evaluation results show that SAEB outperforms conventional blockcipher-based AEAD modes of operation in various performance metrics for lightweight cryptography.