Practical Related-Key Forgery Attacks on Full-Round TinyJAMBU-192/256

Abstract

TinyJAMBU is one of the finalists in the NIST lightweight cryptography competition. It is considered to be one of the more efficient ciphers in the competition and has undergone extensive analysis in recent years as both the keyed permutation as well as the mode are new designs. In this paper we present a related-key forgery attack on the updated TinyJAMBU-v2 scheme with 256- and 192-bit keys. We introduce a high probability related-key differential attack where the differences are only introduced into the key state. Therefore, the characteristic is applicable to the TinyJAMBU mode and can be used to mount a forgery attack. The time and data complexity of the forgery are 2³³ using 2¹⁴ related-keys for the 256-bit key version, and 2⁴³ using 2¹⁶ related-keys for the 192-bit key version.
For the 128-bit key we construct a related-key differential characteristic on the full keyed permutation of TinyJAMBU with a probability of 2⁻¹⁶. We extend the relatedkey differential characteristics on TinyJAMBU to practical-time key-recovery attacks that extract the full key from the keyed permutation with a time and data complexity of 2²⁴, 2²¹, and 2¹⁹ for respectively the 128-, 192-, and 256-bit key variants.
All characteristics are experimentally verified and we provide key nonce pairs that produce the same tag to show the feasibility of the forgery attack. We note that the designers do not claim related-key security, however, the attacks proposed in this paper suggest that the scheme is not key-commiting, which has been recently identified as a favorable property for AEAD schemes.