def sel_val

bend-collections-laws-crypto@1.0.0.0 · proofs/crypto/ed25519/scalar2.bend:101

import Base
import bend-collections-laws-crypto@1.0.0.0/spec/crypto/curve25519/field.bend as FS
import bend-collections-laws-crypto@1.0.0.0/src/crypto/curve25519/field.bend as F
import bend-collections-laws-crypto@1.0.0.0/proofs/lib/logic.bend as L
import bend-collections-laws-crypto@1.0.0.0/proofs/lib/arith.bend as AR
import bend-collections-laws-crypto@1.0.0.0/proofs/crypto/curve25519/limbs.bend as LM
import bend-collections-laws-crypto@1.0.0.0/proofs/crypto/curve25519/fieldops.bend as FO
import bend-collections-laws-crypto@1.0.0.0/proofs/crypto/curve25519/xbits.bend as XB

101def sel_val(+one: Nat, +h1: {one == 1n : Nat}, +kb: U32, +b: Nat, +hk: {v(kb) == b : Nat}, +hb: {Nat.is_le(b, 1n) == True{} : Bool}, +s: List<&2, U32>, +hs: {LM.okb(32n, s, 255n) == True{} : Bool}) -> {FS.value(F.select(kb, F.zero(), s)) == Nat.mul(b, FS.value(s)) : Nat}:
102  match b:
103    case 0n:
104      %Equal.sym(U32, kb, 0, XB.u0(kb, hk)) : {FS.value(F.select(_, F.zero(), s)) == 0n : Nat}
105      %Equal.sym(List<&2, U32>, F.select(0, F.zero(), s), F.zero(), FO.select0(one, h1, 32n, F.zero(), s, {==}, hs)) : {FS.value(_) == 0n : Nat}
106      {==}
107    case 1n:
108      %Equal.sym(U32, kb, 1, XB.u1(kb, hk)) : {FS.value(F.select(_, F.zero(), s)) == Nat.mul(1n, FS.value(s)) : Nat}
109      %Equal.sym(List<&2, U32>, F.select(1, F.zero(), s), s, FO.select1(one, h1, 32n, F.zero(), s, {==}, hs)) : {FS.value(_) == Nat.mul(1n, FS.value(s)) : Nat}
110      Equal.sym(Nat, Nat.mul(1n, FS.value(s)), FS.value(s), AR.one_mul(FS.value(s)))
111    case 2n+q:
112      Empty.absurd({FS.value(F.select(kb, F.zero(), s)) == Nat.mul(2n+q, FS.value(s)) : Nat}, L.false_true(hb))