Merge pull request #1202 from mir-protocol/keccak-preimage

Keccak STARK: constrain preimage to equal A on first round
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Nicholas Ward 2023-09-11 09:05:55 -07:00 committed by GitHub
commit d1c395ef75
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@ -261,6 +261,8 @@ 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);
@ -271,6 +273,13 @@ 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);
}
}
@ -436,6 +445,8 @@ 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);
@ -452,6 +463,21 @@ 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);
}
}