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from __future__ import annotations

import hashlib

import random

def keystream(key: bytes, length: int) -> bytes:

out = bytearray()

ctr = 0

while len(out) < length:

out.extend(hashlib.sha256(key + ctr.to_bytes(8, 'big')).digest())

ctr += 1

return bytes(out[:length])

def stream_xor(data: bytes, key: bytes) -> bytes:

ks = keystream(key, len(data))

return bytes((a ^ b for a, b in zip(data, ks)))

def make_perm(key: bytes) -> bytes:

seed = int.from_bytes(hashlib.sha256(key).digest(), 'big')

rng = random.Random(seed)

perm = list(range(256))

rng.shuffle(perm)

return bytes(perm)

def invert_perm(perm: bytes) -> bytes:

inv = bytearray(256)

for i, p in enumerate(perm):

inv[p] = i

return bytes(inv)

def perm_apply(data: bytes, key: bytes) -> bytes:

perm = make_perm(key)

return bytes((perm[b] for b in data))

def perm_invert(data: bytes, key: bytes) -> bytes:

inv = invert_perm(make_perm(key))

return bytes((inv[b] for b in data))

def _rot_left(b: int, n: int) -> int:

n &= 7

if not n:

return b

return (b << n | b >> 8 - n) & 255

def rot_apply(data: bytes, key: bytes) -> bytes:

return bytes((_rot_left(b, key[i % len(key)]) for i, b in enumerate(data)))

def rot_invert(data: bytes, key: bytes) -> bytes:

return bytes((_rot_left(b, -key[i % len(key)] & 7) for i, b in enumerate(data)))