IACR News item: 11 November 2022
Orr Dunkelman, Shibam Ghosh, Eran Lambooij
ePrint Report
TinyJAMBU is one of the finalists in the NIST lightweight
standardization competition. This paper presents full round practical
zero-sum distinguishers on the keyed permutation used in TinyJAMBU.
We propose a full round zero-sum distinguisher on the 128- and 192-bit
key variants and a reduced round zero-sum distinguisher for the 256-bit
key variant in the known-key settings. Our best known-key distinguisher
works with $2^{16}$ data/time complexity on the full 128-bit version and with
$2^{23}$ data/time complexity on the full 192-bit version. For the 256-bit ver-
sion, we can distinguish 1152 rounds (out of 1280 rounds) in the known-
key settings. In addition, we present the best zero-sum distinguishers
in the secret-key settings: with complexity $2^{23}$ we can distinguish 544
rounds in the forward direction or 576 rounds in the backward direction.
For finding the zero-sum distinguisher, we bound the algebraic degree of
the TinyJAMBU permutation using the monomial prediction technique
proposed by Hu et al. at ASIACRYPT 2020. We model the monomial
prediction rule on TinyJAMBU in MILP and find upper bounds on the
degree by computing the parity of the number of solutions.
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