def sel_okb

bend-collections-laws-crypto@1.0.0.0 · proofs/crypto/ed25519/scalar2.bend:87

import Base
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/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

87# the selected addend: bit * s
88def sel_okb(+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}) -> {LM.okb(32n, F.select(kb, F.zero(), s), 255n) == True{} : Bool}:
89  match b:
90    case 0n:
91      %Equal.sym(U32, kb, 0, XB.u0(kb, hk)) : {LM.okb(32n, F.select(_, F.zero(), s), 255n) == True{} : Bool}
92      %Equal.sym(List<&2, U32>, F.select(0, F.zero(), s), F.zero(), FO.select0(one, h1, 32n, F.zero(), s, {==}, hs)) : {LM.okb(32n, _, 255n) == True{} : Bool}
93      {==}
94    case 1n:
95      %Equal.sym(U32, kb, 1, XB.u1(kb, hk)) : {LM.okb(32n, F.select(_, F.zero(), s), 255n) == True{} : Bool}
96      %Equal.sym(List<&2, U32>, F.select(1, F.zero(), s), s, FO.select1(one, h1, 32n, F.zero(), s, {==}, hs)) : {LM.okb(32n, _, 255n) == True{} : Bool}
97      hs
98    case 2n+q:
99      Empty.absurd({LM.okb(32n, F.select(kb, F.zero(), s), 255n) == True{} : Bool}, L.false_true(hb))