Forgery Attacks on FlexAE and FlexAEAD


FlexAEAD is one of the round-1 candidates in the ongoing NIST Lightweight Cryptography standardization project. In this note, we show several forgery attacks on FlexAEAD with complexity less than the security bound given by the designers, such as a block reordering attack on full FlexAEAD-128 with estimated success probability about 2^54. Additionally, we show some trivial forgeries and point out domain separation issues.

Cryptography and Coding - IMACC 2019