{-# LANGUAGE OverloadedStrings #-}

module ChaCha (tests) where

import qualified Crypto.Cipher.ChaCha as ChaCha
import Imports

import qualified Data.ByteString as B

b8_128_k0_i0 =
    "\xe2\x8a\x5f\xa4\xa6\x7f\x8c\x5d\xef\xed\x3e\x6f\xb7\x30\x34\x86\xaa\x84\x27\xd3\x14\x19\xa7\x29\x57\x2d\x77\x79\x53\x49\x11\x20\xb6\x4a\xb8\xe7\x2b\x8d\xeb\x85\xcd\x6a\xea\x7c\xb6\x08\x9a\x10\x18\x24\xbe\xeb\x08\x81\x4a\x42\x8a\xab\x1f\xa2\xc8\x16\x08\x1b\x8a\x26\xaf\x44\x8a\x1b\xa9\x06\x36\x8f\xd8\xc8\x38\x31\xc1\x8c\xec\x8c\xed\x81\x1a\x02\x8e\x67\x5b\x8d\x2b\xe8\xfc\xe0\x81\x16\x5c\xea\xe9\xf1\xd1\xb7\xa9\x75\x49\x77\x49\x48\x05\x69\xce\xb8\x3d\xe6\xa0\xa5\x87\xd4\x98\x4f\x19\x92\x5f\x5d\x33\x8e\x43\x0d"

b12_128_k0_i0 =
    "\xe1\x04\x7b\xa9\x47\x6b\xf8\xff\x31\x2c\x01\xb4\x34\x5a\x7d\x8c\xa5\x79\x2b\x0a\xd4\x67\x31\x3f\x1d\xc4\x12\xb5\xfd\xce\x32\x41\x0d\xea\x8b\x68\xbd\x77\x4c\x36\xa9\x20\xf0\x92\xa0\x4d\x3f\x95\x27\x4f\xbe\xff\x97\xbc\x84\x91\xfc\xef\x37\xf8\x59\x70\xb4\x50\x1d\x43\xb6\x1a\x8f\x7e\x19\xfc\xed\xde\xf3\x68\xae\x6b\xfb\x11\x10\x1b\xd9\xfd\x3e\x4d\x12\x7d\xe3\x0d\xb2\xdb\x1b\x47\x2e\x76\x42\x68\x03\xa4\x5e\x15\xb9\x62\x75\x19\x86\xef\x1d\x9d\x50\xf5\x98\xa5\xdc\xdc\x9f\xa5\x29\xa2\x83\x57\x99\x1e\x78\x4e\xa2\x0f"

b20_128_k0_i0 =
    "\x89\x67\x09\x52\x60\x83\x64\xfd\x00\xb2\xf9\x09\x36\xf0\x31\xc8\xe7\x56\xe1\x5d\xba\x04\xb8\x49\x3d\x00\x42\x92\x59\xb2\x0f\x46\xcc\x04\xf1\x11\x24\x6b\x6c\x2c\xe0\x66\xbe\x3b\xfb\x32\xd9\xaa\x0f\xdd\xfb\xc1\x21\x23\xd4\xb9\xe4\x4f\x34\xdc\xa0\x5a\x10\x3f\x6c\xd1\x35\xc2\x87\x8c\x83\x2b\x58\x96\xb1\x34\xf6\x14\x2a\x9d\x4d\x8d\x0d\x8f\x10\x26\xd2\x0a\x0a\x81\x51\x2c\xbc\xe6\xe9\x75\x8a\x71\x43\xd0\x21\x97\x80\x22\xa3\x84\x14\x1a\x80\xce\xa3\x06\x2f\x41\xf6\x7a\x75\x2e\x66\xad\x34\x11\x98\x4c\x78\x7e\x30\xad"

b8_256_k0_i0 =
    "\x3e\x00\xef\x2f\x89\x5f\x40\xd6\x7f\x5b\xb8\xe8\x1f\x09\xa5\xa1\x2c\x84\x0e\xc3\xce\x9a\x7f\x3b\x18\x1b\xe1\x88\xef\x71\x1a\x1e\x98\x4c\xe1\x72\xb9\x21\x6f\x41\x9f\x44\x53\x67\x45\x6d\x56\x19\x31\x4a\x42\xa3\xda\x86\xb0\x01\x38\x7b\xfd\xb8\x0e\x0c\xfe\x42\xd2\xae\xfa\x0d\xea\xa5\xc1\x51\xbf\x0a\xdb\x6c\x01\xf2\xa5\xad\xc0\xfd\x58\x12\x59\xf9\xa2\xaa\xdc\xf2\x0f\x8f\xd5\x66\xa2\x6b\x50\x32\xec\x38\xbb\xc5\xda\x98\xee\x0c\x6f\x56\x8b\x87\x2a\x65\xa0\x8a\xbf\x25\x1d\xeb\x21\xbb\x4b\x56\xe5\xd8\x82\x1e\x68\xaa"

b12_256_k0_i0 =
    "\x9b\xf4\x9a\x6a\x07\x55\xf9\x53\x81\x1f\xce\x12\x5f\x26\x83\xd5\x04\x29\xc3\xbb\x49\xe0\x74\x14\x7e\x00\x89\xa5\x2e\xae\x15\x5f\x05\x64\xf8\x79\xd2\x7a\xe3\xc0\x2c\xe8\x28\x34\xac\xfa\x8c\x79\x3a\x62\x9f\x2c\xa0\xde\x69\x19\x61\x0b\xe8\x2f\x41\x13\x26\xbe\x0b\xd5\x88\x41\x20\x3e\x74\xfe\x86\xfc\x71\x33\x8c\xe0\x17\x3d\xc6\x28\xeb\xb7\x19\xbd\xcb\xcc\x15\x15\x85\x21\x4c\xc0\x89\xb4\x42\x25\x8d\xcd\xa1\x4c\xf1\x11\xc6\x02\xb8\x97\x1b\x8c\xc8\x43\xe9\x1e\x46\xca\x90\x51\x51\xc0\x27\x44\xa6\xb0\x17\xe6\x93\x16"

b20_256_k0_i0 =
    "\x76\xb8\xe0\xad\xa0\xf1\x3d\x90\x40\x5d\x6a\xe5\x53\x86\xbd\x28\xbd\xd2\x19\xb8\xa0\x8d\xed\x1a\xa8\x36\xef\xcc\x8b\x77\x0d\xc7\xda\x41\x59\x7c\x51\x57\x48\x8d\x77\x24\xe0\x3f\xb8\xd8\x4a\x37\x6a\x43\xb8\xf4\x15\x18\xa1\x1c\xc3\x87\xb6\x69\xb2\xee\x65\x86\x9f\x07\xe7\xbe\x55\x51\x38\x7a\x98\xba\x97\x7c\x73\x2d\x08\x0d\xcb\x0f\x29\xa0\x48\xe3\x65\x69\x12\xc6\x53\x3e\x32\xee\x7a\xed\x29\xb7\x21\x76\x9c\xe6\x4e\x43\xd5\x71\x33\xb0\x74\xd8\x39\xd5\x31\xed\x1f\x28\x51\x0a\xfb\x45\xac\xe1\x0a\x1f\x4b\x79\x4d\x6f"

-- XChaCha20 test vector from RFC draft: https://datatracker.ietf.org/doc/html/draft-arciszewski-xchacha

xChaCha20_ExampleKAT = expected @=? fst (ChaCha.combine initState plaintext)
  where
    iv = B.pack $ [0x40 .. 0x56] ++ [0x58]
    key = B.pack [0x80 .. 0x9f]
    initState = ChaCha.initializeX 20 key iv
    plaintext :: B.ByteString
    plaintext =
        "The dhole (pronounced \"dole\") is also known as the Asiatic wild dog, red dog, and whistling dog. It is about the size of a German shepherd but looks more like a long-legged fox. This highly elusive and skilled jumper is classified with wolves, coyotes, jackals, and foxes in the taxonomic family Canidae."
    expected :: B.ByteString
    expected =
        "\x45\x59\xab\xba\x4e\x48\xc1\x61\x02\xe8\xbb\x2c\x05\xe6\x94\x7f\x50\xa7\x86\xde\x16\x2f\x9b\x0b\x7e\x59\x2a\x9b\x53\xd0\xd4\xe9\x8d\x8d\x64\x10\xd5\x40\xa1\xa6\x37\x5b\x26\xd8\x0d\xac\xe4\xfa\xb5\x23\x84\xc7\x31\xac\xbf\x16\xa5\x92\x3c\x0c\x48\xd3\x57\x5d\x4d\x0d\x2c\x67\x3b\x66\x6f\xaa\x73\x10\x61\x27\x77\x01\x09\x3a\x6b\xf7\xa1\x58\xa8\x86\x42\x92\xa4\x1c\x48\xe3\xa9\xb4\xc0\xda\xec\xe0\xf8\xd9\x8d\x0d\x7e\x05\xb3\x7a\x30\x7b\xbb\x66\x33\x31\x64\xec\x9e\x1b\x24\xea\x0d\x6c\x3f\xfd\xdc\xec\x4f\x68\xe7\x44\x30\x56\x19\x3a\x03\xc8\x10\xe1\x13\x44\xca\x06\xd8\xed\x8a\x2b\xfb\x1e\x8d\x48\xcf\xa6\xbc\x0e\xb4\xe2\x46\x4b\x74\x81\x42\x40\x7c\x9f\x43\x1a\xee\x76\x99\x60\xe1\x5b\xa8\xb9\x68\x90\x46\x6e\xf2\x45\x75\x99\x85\x23\x85\xc6\x61\xf7\x52\xce\x20\xf9\xda\x0c\x09\xab\x6b\x19\xdf\x74\xe7\x6a\x95\x96\x74\x46\xf8\xd0\xfd\x41\x5e\x7b\xee\x2a\x12\xa1\x14\xc2\x0e\xb5\x29\x2a\xe7\xa3\x49\xae\x57\x78\x20\xd5\x52\x0a\x1f\x3f\xb6\x2a\x17\xce\x6a\x7e\x68\xfa\x7c\x79\x11\x1d\x88\x60\x92\x0b\xc0\x48\xef\x43\xfe\x84\x48\x6c\xcb\x87\xc2\x5f\x0a\xe0\x45\xf0\xcc\xe1\xe7\x98\x9a\x9a\xa2\x20\xa2\x8b\xdd\x48\x27\xe7\x51\xa2\x4a\x6d\x5c\x62\xd7\x90\xa6\x63\x93\xb9\x31\x11\xc1\xa5\x5d\xd7\x42\x1a\x10\x18\x49\x74\xc7\xc5"

rfc8439A2_1 = cipher @=? cipher'
  where
    key :: ByteString
    key =
        "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
    nonce :: ByteString
    nonce = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
    plain :: ByteString
    plain =
        "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
    cipher :: ByteString
    cipher =
        "\x76\xb8\xe0\xad\xa0\xf1\x3d\x90\x40\x5d\x6a\xe5\x53\x86\xbd\x28\xbd\xd2\x19\xb8\xa0\x8d\xed\x1a\xa8\x36\xef\xcc\x8b\x77\x0d\xc7\xda\x41\x59\x7c\x51\x57\x48\x8d\x77\x24\xe0\x3f\xb8\xd8\x4a\x37\x6a\x43\xb8\xf4\x15\x18\xa1\x1c\xc3\x87\xb6\x69\xb2\xee\x65\x86"
    cipher' = fst $ ChaCha.combine (ChaCha.initialize 20 key nonce) plain

rfc8439A2_2 = cipher @=? cipher'
  where
    key :: ByteString
    key =
        "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01"
    nonce :: ByteString
    nonce = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02"
    plain :: ByteString
    plain =
        "\x41\x6e\x79\x20\x73\x75\x62\x6d\x69\x73\x73\x69\x6f\x6e\x20\x74\x6f\x20\x74\x68\x65\x20\x49\x45\x54\x46\x20\x69\x6e\x74\x65\x6e\x64\x65\x64\x20\x62\x79\x20\x74\x68\x65\x20\x43\x6f\x6e\x74\x72\x69\x62\x75\x74\x6f\x72\x20\x66\x6f\x72\x20\x70\x75\x62\x6c\x69\x63\x61\x74\x69\x6f\x6e\x20\x61\x73\x20\x61\x6c\x6c\x20\x6f\x72\x20\x70\x61\x72\x74\x20\x6f\x66\x20\x61\x6e\x20\x49\x45\x54\x46\x20\x49\x6e\x74\x65\x72\x6e\x65\x74\x2d\x44\x72\x61\x66\x74\x20\x6f\x72\x20\x52\x46\x43\x20\x61\x6e\x64\x20\x61\x6e\x79\x20\x73\x74\x61\x74\x65\x6d\x65\x6e\x74\x20\x6d\x61\x64\x65\x20\x77\x69\x74\x68\x69\x6e\x20\x74\x68\x65\x20\x63\x6f\x6e\x74\x65\x78\x74\x20\x6f\x66\x20\x61\x6e\x20\x49\x45\x54\x46\x20\x61\x63\x74\x69\x76\x69\x74\x79\x20\x69\x73\x20\x63\x6f\x6e\x73\x69\x64\x65\x72\x65\x64\x20\x61\x6e\x20\x22\x49\x45\x54\x46\x20\x43\x6f\x6e\x74\x72\x69\x62\x75\x74\x69\x6f\x6e\x22\x2e\x20\x53\x75\x63\x68\x20\x73\x74\x61\x74\x65\x6d\x65\x6e\x74\x73\x20\x69\x6e\x63\x6c\x75\x64\x65\x20\x6f\x72\x61\x6c\x20\x73\x74\x61\x74\x65\x6d\x65\x6e\x74\x73\x20\x69\x6e\x20\x49\x45\x54\x46\x20\x73\x65\x73\x73\x69\x6f\x6e\x73\x2c\x20\x61\x73\x20\x77\x65\x6c\x6c\x20\x61\x73\x20\x77\x72\x69\x74\x74\x65\x6e\x20\x61\x6e\x64\x20\x65\x6c\x65\x63\x74\x72\x6f\x6e\x69\x63\x20\x63\x6f\x6d\x6d\x75\x6e\x69\x63\x61\x74\x69\x6f\x6e\x73\x20\x6d\x61\x64\x65\x20\x61\x74\x20\x61\x6e\x79\x20\x74\x69\x6d\x65\x20\x6f\x72\x20\x70\x6c\x61\x63\x65\x2c\x20\x77\x68\x69\x63\x68\x20\x61\x72\x65\x20\x61\x64\x64\x72\x65\x73\x73\x65\x64\x20\x74\x6f"
    cipher :: ByteString
    cipher =
        "\xa3\xfb\xf0\x7d\xf3\xfa\x2f\xde\x4f\x37\x6c\xa2\x3e\x82\x73\x70\x41\x60\x5d\x9f\x4f\x4f\x57\xbd\x8c\xff\x2c\x1d\x4b\x79\x55\xec\x2a\x97\x94\x8b\xd3\x72\x29\x15\xc8\xf3\xd3\x37\xf7\xd3\x70\x05\x0e\x9e\x96\xd6\x47\xb7\xc3\x9f\x56\xe0\x31\xca\x5e\xb6\x25\x0d\x40\x42\xe0\x27\x85\xec\xec\xfa\x4b\x4b\xb5\xe8\xea\xd0\x44\x0e\x20\xb6\xe8\xdb\x09\xd8\x81\xa7\xc6\x13\x2f\x42\x0e\x52\x79\x50\x42\xbd\xfa\x77\x73\xd8\xa9\x05\x14\x47\xb3\x29\x1c\xe1\x41\x1c\x68\x04\x65\x55\x2a\xa6\xc4\x05\xb7\x76\x4d\x5e\x87\xbe\xa8\x5a\xd0\x0f\x84\x49\xed\x8f\x72\xd0\xd6\x62\xab\x05\x26\x91\xca\x66\x42\x4b\xc8\x6d\x2d\xf8\x0e\xa4\x1f\x43\xab\xf9\x37\xd3\x25\x9d\xc4\xb2\xd0\xdf\xb4\x8a\x6c\x91\x39\xdd\xd7\xf7\x69\x66\xe9\x28\xe6\x35\x55\x3b\xa7\x6c\x5c\x87\x9d\x7b\x35\xd4\x9e\xb2\xe6\x2b\x08\x71\xcd\xac\x63\x89\x39\xe2\x5e\x8a\x1e\x0e\xf9\xd5\x28\x0f\xa8\xca\x32\x8b\x35\x1c\x3c\x76\x59\x89\xcb\xcf\x3d\xaa\x8b\x6c\xcc\x3a\xaf\x9f\x39\x79\xc9\x2b\x37\x20\xfc\x88\xdc\x95\xed\x84\xa1\xbe\x05\x9c\x64\x99\xb9\xfd\xa2\x36\xe7\xe8\x18\xb0\x4b\x0b\xc3\x9c\x1e\x87\x6b\x19\x3b\xfe\x55\x69\x75\x3f\x88\x12\x8c\xc0\x8a\xaa\x9b\x63\xd1\xa1\x6f\x80\xef\x25\x54\xd7\x18\x9c\x41\x1f\x58\x69\xca\x52\xc5\xb8\x3f\xa3\x6f\xf2\x16\xb9\xc1\xd3\x00\x62\xbe\xbc\xfd\x2d\xc5\xbc\xe0\x91\x19\x34\xfd\xa7\x9a\x86\xf6\xe6\x98\xce\xd7\x59\xc3\xff\x9b\x64\x77\x33\x8f\x3d\xa4\xf9\xcd\x85\x14\xea\x99\x82\xcc\xaf\xb3\x41\xb2\x38\x4d\xd9\x02\xf3\xd1\xab\x7a\xc6\x1d\xd2\x9c\x6f\x21\xba\x5b\x86\x2f\x37\x30\xe3\x7c\xfd\xc4\xfd\x80\x6c\x22\xf2\x21"
    cipher' =
        fst $
            ChaCha.combine (ChaCha.setCounter32 1 (ChaCha.initialize 20 key nonce)) plain

rfc8439A2_3 = cipher @=? cipher'
  where
    key :: ByteString
    key =
        "\x1c\x92\x40\xa5\xeb\x55\xd3\x8a\xf3\x33\x88\x86\x04\xf6\xb5\xf0\x47\x39\x17\xc1\x40\x2b\x80\x09\x9d\xca\x5c\xbc\x20\x70\x75\xc0"
    nonce :: ByteString
    nonce = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02"
    plain :: ByteString
    plain =
        "\x27\x54\x77\x61\x73\x20\x62\x72\x69\x6c\x6c\x69\x67\x2c\x20\x61\x6e\x64\x20\x74\x68\x65\x20\x73\x6c\x69\x74\x68\x79\x20\x74\x6f\x76\x65\x73\x0a\x44\x69\x64\x20\x67\x79\x72\x65\x20\x61\x6e\x64\x20\x67\x69\x6d\x62\x6c\x65\x20\x69\x6e\x20\x74\x68\x65\x20\x77\x61\x62\x65\x3a\x0a\x41\x6c\x6c\x20\x6d\x69\x6d\x73\x79\x20\x77\x65\x72\x65\x20\x74\x68\x65\x20\x62\x6f\x72\x6f\x67\x6f\x76\x65\x73\x2c\x0a\x41\x6e\x64\x20\x74\x68\x65\x20\x6d\x6f\x6d\x65\x20\x72\x61\x74\x68\x73\x20\x6f\x75\x74\x67\x72\x61\x62\x65\x2e"
    cipher :: ByteString
    cipher =
        "\x62\xe6\x34\x7f\x95\xed\x87\xa4\x5f\xfa\xe7\x42\x6f\x27\xa1\xdf\x5f\xb6\x91\x10\x04\x4c\x0d\x73\x11\x8e\xff\xa9\x5b\x01\xe5\xcf\x16\x6d\x3d\xf2\xd7\x21\xca\xf9\xb2\x1e\x5f\xb1\x4c\x61\x68\x71\xfd\x84\xc5\x4f\x9d\x65\xb2\x83\x19\x6c\x7f\xe4\xf6\x05\x53\xeb\xf3\x9c\x64\x02\xc4\x22\x34\xe3\x2a\x35\x6b\x3e\x76\x43\x12\xa6\x1a\x55\x32\x05\x57\x16\xea\xd6\x96\x25\x68\xf8\x7d\x3f\x3f\x77\x04\xc6\xa8\xd1\xbc\xd1\xbf\x4d\x50\xd6\x15\x4b\x6d\xa7\x31\xb1\x87\xb5\x8d\xfd\x72\x8a\xfa\x36\x75\x7a\x79\x7a\xc1\x88\xd1"
    cipher' =
        fst $
            ChaCha.combine (ChaCha.setCounter32 42 (ChaCha.initialize 20 key nonce)) plain

data Vector
    = Vector
        Int -- rounds
        ByteString -- key
        ByteString -- nonce
    deriving (Show, Eq)

instance Arbitrary Vector where
    arbitrary = Vector 20 <$> arbitraryBS 16 <*> arbitraryBS 12

tests =
    testGroup
        "ChaCha"
        [ testCase "8-128-K0-I0" (chachaRunSimple b8_128_k0_i0 8 16 8)
        , testCase "12-128-K0-I0" (chachaRunSimple b12_128_k0_i0 12 16 8)
        , testCase "20-128-K0-I0" (chachaRunSimple b20_128_k0_i0 20 16 8)
        , testCase "8-256-K0-I0" (chachaRunSimple b8_256_k0_i0 8 32 8)
        , testCase "12-256-K0-I0" (chachaRunSimple b12_256_k0_i0 12 32 8)
        , testCase "20-256-K0-I0" (chachaRunSimple b20_256_k0_i0 20 32 8)
        , testCase "XChaCha20 example KAT" xChaCha20_ExampleKAT
        , testCase "RFC 8439 A2 #1 ChaCha20" rfc8439A2_1
        , testCase "RFC 8439 A2 #2 ChaCha20" rfc8439A2_2
        , testCase "RFC 8439 A2 #3 ChaCha20" rfc8439A2_3
        , testProperty "generate-combine" chachaGenerateCombine
        , testProperty "chunking-generate" chachaGenerateChunks
        , testProperty "chunking-combine" chachaCombineChunks
        ]
  where
    chachaRunSimple expected rounds klen nonceLen =
        let chacha = ChaCha.initialize rounds (B.replicate klen 0) (B.replicate nonceLen 0)
         in expected @=? fst (ChaCha.generate chacha (B.length expected))

    chachaGenerateChunks :: ChunkingLen -> Vector -> Bool
    chachaGenerateChunks (ChunkingLen ckLen) (Vector rounds key iv) =
        let initChaCha = ChaCha.initialize rounds key iv
            nbBytes = 1048
            (expected, _) = ChaCha.generate initChaCha nbBytes
            chunks = loop nbBytes ckLen initChaCha
         in expected `propertyEq` B.concat chunks
      where
        loop n [] chacha = loop n ckLen chacha
        loop 0 _ _ = []
        loop n (x : xs) chacha =
            let len = min x n
                (c, next) = ChaCha.generate chacha len
             in c : loop (n - len) xs next

    chachaGenerateCombine :: ChunkingLen0_127 -> Vector -> Int0_2901 -> Bool
    chachaGenerateCombine (ChunkingLen0_127 ckLen) (Vector rounds key iv) (Int0_2901 nbBytes) =
        let initChaCha = ChaCha.initialize rounds key iv
         in loop nbBytes ckLen initChaCha
      where
        loop n [] chacha = loop n ckLen chacha
        loop 0 _ _ = True
        loop n (x : xs) chacha =
            let len = min x n
                (c1, next) = ChaCha.generate chacha len
                (c2, _) = ChaCha.combine chacha (B.replicate len 0)
             in if c1 == c2 then loop (n - len) xs next else False

    chachaCombineChunks :: ChunkingLen0_127 -> Vector -> ArbitraryBS0_2901 -> Bool
    chachaCombineChunks (ChunkingLen0_127 ckLen) (Vector rounds key iv) (ArbitraryBS0_2901 wholebs) =
        let initChaCha = ChaCha.initialize rounds key iv
            (expected, _) = ChaCha.combine initChaCha wholebs
            chunks = loop wholebs ckLen initChaCha
         in expected `propertyEq` B.concat chunks
      where
        loop bs [] chacha = loop bs ckLen chacha
        loop bs (x : xs) chacha
            | B.null bs = []
            | otherwise =
                let (bs1, bs2) = B.splitAt (min x (B.length bs)) bs
                    (c, next) = ChaCha.combine chacha bs1
                 in c : loop bs2 xs next
