def o_sel

bend-collections-laws-crypto@1.0.0.0 · proofs/crypto/curve25519/ladder.bend:39

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

39def o_sel(+one: Nat, +h1: {one == 1n : Nat}, +sw: U32, +s: Nat, +hs: {v(sw) == s : Nat}, +hb: {Nat.is_le(s, 1n) == True{} : Bool}, +a: List<&2, U32>, +b: List<&2, U32>, +oa: {LM.okb(32n, a, 255n) == True{} : Bool}, +ob: {LM.okb(32n, b, 255n) == True{} : Bool}) -> {LM.okb(32n, F.select(sw, a, b), 255n) == True{} : Bool}:
40  match s:
41    case 0n:
42      %Equal.sym(U32, sw, 0, XB.u0(sw, hs)) : {LM.okb(32n, F.select(_, a, b), 255n) == True{} : Bool}
43      %Equal.sym(List<&2, U32>, F.select(0, a, b), a, FO.select0(one, h1, 32n, a, b, oa, ob)) : {LM.okb(32n, _, 255n) == True{} : Bool}
44      oa
45    case 1n:
46      %Equal.sym(U32, sw, 1, XB.u1(sw, hs)) : {LM.okb(32n, F.select(_, a, b), 255n) == True{} : Bool}
47      %Equal.sym(List<&2, U32>, F.select(1, a, b), b, FO.select1(one, h1, 32n, a, b, oa, ob)) : {LM.okb(32n, _, 255n) == True{} : Bool}
48      ob
49    case 2n+q:
50      Empty.absurd({LM.okb(32n, F.select(sw, a, b), 255n) == True{} : Bool}, L.false_true(hb))