def okb_bytes

bend-collections-laws-crypto@1.0.0.0 · proofs/crypto/curve25519/limbs.bend:129

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/proofs/lib/nat.bend as N
import bend-collections-laws-crypto@1.0.0.0/proofs/lib/logic.bend as L

129def okb_bytes(+n: Nat, +xs: List<&2, U32>, +e: {okb(n, xs, 255n) == True{} : Bool}) -> {FS.bytes_ok(n, xs) == True{} : Bool}:
130  match n xs:
131    case 0n Nil{}:
132      {==}
133    case 0n Con{y, yt}:
134      Empty.absurd({FS.bytes_ok(0n, Con{y, yt}) == True{} : Bool}, L.false_true(e))
135    case 1n+m Nil{}:
136      Empty.absurd({FS.bytes_ok(1n+m, Nil{}) == True{} : Bool}, L.false_true(e))
137    case 1n+ +m Con{+y, +yt}:
138      L.and_intro(Nat.is_lt(v(y), 256n), FS.bytes_ok(m, yt), N.le_lt_succ(v(y), 255n, okb_head(m, y, yt, 255n, e)), okb_bytes(m, yt, okb_tail(m, y, yt, 255n, e)))