Cryptanalysis of Hummingbird-1

Abstract

Hummingbird-1 is a lightweight encryption and message authentication primitive published in RISC ’09 and WLC ’10. Hummingbird-1 utilizes a 256-bit secret key and a 64-bit IV. We report a chosen-IV, chosen-message attack that can recover the full secret key with a few million chosen messages processed under two related IVs. The attack requires at most 264 off-line computational effort. The attack has been implemented and demonstrated to work against a real-life implementation of Hummingbird-1. By attacking the differentially weak E component, the overall attack complexity can be reduced by a significant factor. Our cryptanalysis is based on a differential divide-and-conquer method with some novel techniques that are uniquely applicable to ciphers of this type.