ourCrypto.py

from Cryptodome.Cipher import AES
import hashlib

import util

iv = b"ourWalletCryptoX"

def encrypt(plain_text, key):
    key = hashlib.sha256(hashlib.sha256(key).digest()).digest()[:16]
    return AES.new(key, AES.MODE_CFB, iv).encrypt(str.encode(plain_text))

def decrypt(enc_text, key):
    key = hashlib.sha256(hashlib.sha256(key).digest()).digest()[:16]
    try:
        return AES.new(key, AES.MODE_CFB, iv).decrypt(enc_text).decode()
    except:
        pass
    return None

def is_signature_standard(der_signature_bytes):
    der_signature_bytes = bytearray(der_signature_bytes)
    size_r = der_signature_bytes[3]
    size_s = der_signature_bytes[4+size_r+1]
    pos_s = 7+size_r
    s = der_signature_bytes[pos_s:pos_s+size_s]
    s_dec = int.from_bytes(s, "big")
    N = 115792089237316195423570985008687907852837564279074904382605163141518161494337
    return s_dec < N/2

def normalize(der_signature_bytes):
    raise NotImplementedErrro

    der_signature_bytes = bytearray(der_signature_bytes)
    size_r = der_signature_bytes[3]
    size_s = der_signature_bytes[4+size_r+1]
    pos_s = 7+size_r
    r = der_signature_bytes[    4:    4+size_r]
    s = der_signature_bytes[pos_s:pos_s+size_s]
    r_dec = int.from_bytes(r, "big")
    s_dec = int.from_bytes(s, "big")
    N = 115792089237316195423570985008687907852837564279074904382605163141518161494337
    print("N", N)
    print("s_dec", s_dec)
    print("s", s.hex())
    if s_dec > N/2:
        print("s", s)
        print("r", r)
        s_dec = N - s_dec
        new_s = util.int_to_bytes(s_dec)
        print("s_dec", s.hex())
        print("new_s", new_s.hex())
        size_difference = len(s) - len(new_s)
        print("size_difference", size_difference)
        print("der_signature_bytes.hex()", der_signature_bytes.hex())
        der_signature_bytes[pos_s:pos_s+size_s] = new_s
        der_signature_bytes[4+size_r+1] -= size_difference
        der_signature_bytes[         1] -= size_difference
        print("normalized")
        print("der_signature_bytes.hex()", der_signature_bytes.hex())
    return der_signature_bytes

if __name__ == "__main__":
    plaintext = b"Testing AES encryption/decryption in techieshouts.com"
    key = b"YourSampleEncKey"
    print("Plain text: ",plaintext)
    print("Calling encryption library")
    encryptedtext = encrypt(plaintext,key)
    print("Encrypted text")
    print(encryptedtext.hex())
    decryptedtext = decrypt(encryptedtext,key)
    print("Decrypted text")
    print(decryptedtext)