Laws.Expand.prefix: law of bend-collections-laws-crypto@1.0.0.0
Import: import bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/laws.bend as Laws
Lines 52-61 of bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/laws.bend: https://jend.leeeet.dev/read.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/laws.bend&start_line=52&end_line=61

import Base
import bend-collections-laws-crypto@1.0.0.0/src/crypto/kdf.bend as KDF

# A shorter output is a prefix of a longer one (same key and info).
law Expand.prefix:
  for +prk: List<&2, U32>
  for +info: List<&2, U32>
  for +a: Nat
  for +b: Nat
  for +out: List<&2, U32>
  for +hab: {Nat.is_le(a, b) == True{} : Bool}
  for +h: {KDF.expand(prk, info, b) == Done{out} : Result<&2, &2, KDF.KdfError, List<&2, U32>>}
  {KDF.expand(prk, info, a) == Done{List.take(&2, U32, out, a)} : Result<&2, &2, KDF.KdfError, List<&2, U32>>}

Uses (17):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Equal.sym
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=List.take
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Nat.is_le
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Result
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=U32
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/laws.bend&name=Expand.done
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/okm.bend&name=okm_prefix
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/proof.bend&name=done_cong
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/proof.bend&name=done_ok
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/crypto/kdf/proof.bend&name=done_okm
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/proofs/lib/nat.bend&name=le_trans
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/spec/crypto/hkdf.bend&name=okm
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/kdf.bend&name=KdfError
  https://jend.leeeet.dev/definition.txt?path=bend-collections-laws-crypto@1.0.0.0/src/crypto/kdf.bend&name=expand