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Keccak STARK: constraint preimage to equal A on first round

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This commit is contained in:
Nicholas Ward 2023-08-28 12:42:01 -07:00
parent 760f09a8aa
commit ea03e4183f
1 changed files with 26 additions and 0 deletions
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26
evm/src/keccak/keccak_stark.rs
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@ -264,6 +264,8 @@ impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for KeccakStark<F
yield_constr.constraint(not_final_step * filter);
// If this is not the final step, the local and next preimages must match.
// Also, if this is the first step, the preimage must match A.
let is_first_step = vars.local_values[reg_step(0)];
for x in 0..5 {
for y in 0..5 {
let reg_preimage_lo = reg_preimage(x, y);
@ -274,6 +276,13 @@ impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for KeccakStark<F
vars.local_values[reg_preimage_hi] - vars.next_values[reg_preimage_hi];
yield_constr.constraint_transition(not_final_step * diff_lo);
yield_constr.constraint_transition(not_final_step * diff_hi);
let reg_a_lo = reg_a(x, y);
let reg_a_hi = reg_a_lo + 1;
let diff_lo = vars.local_values[reg_preimage_lo] - vars.local_values[reg_a_lo];
let diff_hi = vars.local_values[reg_preimage_hi] - vars.local_values[reg_a_hi];
yield_constr.constraint(is_first_step * diff_lo);
yield_constr.constraint(is_first_step * diff_hi);
}
}
@ -439,6 +448,8 @@ impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for KeccakStark<F
yield_constr.constraint(builder, constraint);
// If this is not the final step, the local and next preimages must match.
// Also, if this is the first step, the preimage must match A.
let is_first_step = vars.local_values[reg_step(0)];
for x in 0..5 {
for y in 0..5 {
let reg_preimage_lo = reg_preimage(x, y);
@ -455,6 +466,21 @@ impl<F: RichField + Extendable<D>, const D: usize> Stark<F, D> for KeccakStark<F
);
let constraint = builder.mul_extension(not_final_step, diff);
yield_constr.constraint_transition(builder, constraint);
let reg_a_lo = reg_a(x, y);
let reg_a_hi = reg_a_lo + 1;
let diff_lo = builder.sub_extension(
vars.local_values[reg_preimage_lo],
vars.local_values[reg_a_lo],
);
let constraint = builder.mul_extension(is_first_step, diff_lo);
yield_constr.constraint(builder, constraint);
let diff_hi = builder.sub_extension(
vars.local_values[reg_preimage_hi],
vars.local_values[reg_a_hi],
);
let constraint = builder.mul_extension(is_first_step, diff_hi);
yield_constr.constraint(builder, constraint);
}
}