AES128 with Shamir

from Crypto.Cipher import AES
from Crypto.Util import Counter
from Crypto.Protocol.SecretSharing import Shamir

# https://legrandin.github.io/pycryptodome/Doc/3.4/Crypto.Protocol.SecretSharing.Shamir-class.html
# https://legrandin.github.io/pycryptodome/Doc/3.4/Crypto.Cipher.AES-module.html
# http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.80.8910&rep=rep1&type=pdf
# https://pypi.python.org/pypi/secretsharing/ # Data-Len is not fixed to 16 byte
# https://pypi.python.org/pypi/subrosa/0.1.0 # better
# http://point-at-infinity.org/ssss/index.html

def make_keys(data=b'', k=2, n=3):
    key = os.urandom(16)
    counter = Counter.new(128)
    aes = AES.new(key, mode=AES.MODE_CTR, counter=counter)
    cipher = aes.encrypt(data)
    keys = Shamir.split(k, n, key)
    keys = [f'{n}-{base64.b64encode(k).decode()}' for n, k in keys]
    return keys, cipher

def decode(keys, data):
    keys = [k.split('-') for k in keys]
    keys = [(int(n), base64.b64decode(k)) for n, k in keys]
    key = Shamir.combine(keys)
    aes = AES.new(key, mode=AES.MODE_CTR, counter=Counter.new(128))
    cleartext = aes.decrypt(data).decode()
    return cleartext

keys, encrypted = make_keys(b'Hello World', 5, 20)
cleartext = decode(keys[5:11], encrypted)
print(cleartext)