Precompile for Poseidon2 BabyBear #1807
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std/machines/hash/poseidon2_bb.asm
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| PARTIAL * (a[i] - x7[i]) + x7[i] | ||
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| // The MDS matrix |
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Can this be shared across the different poseidon implementations?
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No, because the power you use for the S-Box depends on the field. But 7 is used both by BabyBear and Goldilocks.
std/machines/hash/poseidon2_bb.asm
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| pol constant PARTIAL = [0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0]*; | ||
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| // The round constants | ||
| pol constant C_0 = [0xb585f766f2144405, 0x86287821f722c881, 0xe9fa634a21de0082, 0x92a756e67e2b9413, 0x3cc3f892184df408, 0x7131aa45268d7d8c, 0x99ad1aab0814283b, 0xeb84f608da56ef48, 0x7159cd30c3ac118e, 0xdcef0797c2b69ec7, 0xd0762cbc8ca6570c, 0x30a4680593258387, 0x15a16a8a8322d458, 0x5a3f1bb1c53a9645, 0x775005982d74d7f7, 0xf9cc95c22b4c1fcc, 0xc49366bb25e8513, 0xdd611f1000c17442, 0x2ff876fa5ef97c4, 0x3d06c8bd1514e2d9, 0xe89cd854d5d01d33, 0xece5a71e0cfedc75, 0x90004c1371b893c5, 0xde122bebe9a39368, 0x4d61e56a525d225a, 0x1478d361dbbf9fac, 0x475cd3205a3bdcde, 0xe70201e960cb78b8, 0x7be5b9ffda905e1c, 0xf3c12fe54d5c653b, 0x0]*; |
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Can these be shared across the different poseidon implementations?
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No, because the number of rounds depends on the state length, which depends on the field size. Also these constants don't fit in BabyBear (they are just a copy of Goldilocks impl).
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| // External round MDS matrix | ||
| let MDS = [ | ||
| [4, 6, 2, 2, 2, 3, 1, 1, 2, 3, 1, 1, 2, 3, 1, 1], |
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Could we please avoid copying these magic constants across 4-5 files?
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They are not. The only other place most of these constants appear is inside plonky3 rust code.
The best I can do is, after merging this branch with the poseidon_bb one, place a fraction of the big list of random numbers that is common between the two of them in a separate file, as they are the output of the same deterministic RNG.
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Blocked on #1933. |
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