def sp.round_keys

bend-osdev-legacy-ciphers@0.1.0.0 · serpent.bend:326

import Base
import bend-osdev-cipher-modes@0.1.0.0/cipher_modes.bend as M

326# round key K_i = S_((3 - i) mod 8)(w_(4i) .. w_(4i+3)), as an XOR step, for
327# n more round keys from i
328def sp.round_keys(n: Nat, +i: Nat, ws: List<&2, U32>) -> List<&2, M.CmBlock>:
329  match n:
330    case 0n:
331      Nil{}
332    case 1n+p:
333      match ws:
334        case Con{a, Con{b, Con{c, Con{d, t}}}}:
335          Con{sp.sop(sp.box(Nat.sub(35n, i)), False{}, M.CmBlock{a, b, c, d}), sp.round_keys(p, Nat.add(i, 1n), t)}
336        case _:
337          Nil{}