simplify poseidon_safe_domain_separator
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The doc comment previously explained that the function was specific to a single Poseidon permutation. However, it still tried to be generic. As a result the code was more complex than necessary (3 additional generic arguments) and technically broken for any permutation that does not use 24 field elements. Instead it now is indeed specific to the poseidon2 permutation with 24 field elements. For the use case of producing packed data, we simply broadcast the result after calling the function. This is only used in the preamble of the `compute_tree_leaves` code anyway.
tcoratger
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Dec 17, 2025
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Thanks this makes sense since this repo is a specialized version of XMSS for Ethereum so that we don't need the generic thing.
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I started looking at the following two comments:
to see if there was some room for optimization here by precomputing things (I don't believe so;
applyis only called in non hot code paths directly and is the only place where we construct the domain separator on each call). While looking into this, I realized that theposeidon_safe_domain_separatorhelper was more complicated than necessary.The doc comment previously explained that the function was specific to a single Poseidon permutation. However, it still tried to be generic. As a result the code was more complex than necessary (3 additional generic arguments) and technically broken for any permutation that does not use 24 field elements.
Instead it now is indeed specific to the poseidon2 permutation with 24 field elements.
For the use case of producing packed data, we simply broadcast the result after calling the function. This is only used in the preamble of the
compute_tree_leavescode anyway.I personally prefer code less generic than necessary, but I understand if we don't want to merge this.