brain_mnemonic.py

import bisect
import hashlib


def check_mnemonic(word_list: list[str], mnemonic_list: list[str]) -> bool:
    if len(mnemonic_list) not in [12, 15, 18, 21, 24]:
        return False
    try:
        idx = map(lambda x:bin(word_list.index(x))[2:].zfill(11), mnemonic_list)
        b = "".join(idx)
    except ValueError:
        return False
    l = len(b)
    d = b[: l // 33 * 32]
    h = b[-l // 33:]
    nd = int(d, 2).to_bytes(l // 33 * 4, byteorder = "big")
    nh = bin(int(hashlib.sha256(nd).hexdigest(), 16))[2:].zfill(256)[: l // 33]
    return h == nh


def main():
    input_word_list = input("Enter 12, 15, 18, 21 or 24 words separated by spaces >").strip().lower().split(" ")
    if len(input_word_list) not in [12, 15, 18, 21, 24]:
        print(
            "Number of words must be one of the following: [12, 15, 18, 21, 24], but it is not (%d)." % len(input_word_list))
        return
    
    try:
        with open("english.txt", 'r') as f:
            word_list_lines = f.readlines()
            word_list = [line.strip() for line in word_list_lines]

            mnemonic_list = []
            for input_word in input_word_list[:-1]:
                index = bisect.bisect_left(word_list, input_word)
                mnemonic_list.append(word_list[index])

            valid_last_words = []
            for word in word_list:
                if check_mnemonic(word_list, mnemonic_list + [word]):
                    valid_last_words.append(word)

            last_word_index = bisect.bisect_left(valid_last_words, input_word_list[-1])
            mnemonic_list.append(valid_last_words[last_word_index])
            print(" ".join(mnemonic_list))

    except FileNotFoundError:
        print("english.txt not found, please download it from "
              "https://github.com/bitcoin/bips/blob/master/bip-0039/english.txt")


if __name__ == "__main__":
    main()