hide.py 文件源码

def encrypt(data, password, padding=0):
    """Encrypts data using the password.

    Encrypts the data using the provided password using the cryptography module.
    The password is converted into a base64-encoded key which is then used in a
    symmetric encryption algorithm.
    """

    if padding < 0:
        print "Image too small to encode the file. \
You can store 1 byte per pixel."
        exit()

    password = bytes(password)

    #Use key stretching to generate a secure key
    kdf = PBKDF2HMAC(
        algorithm=hashes.SHA256(),
        length=32,
        salt=bytes(password),
        iterations=100000,
        backend=default_backend())

    key = kdf.derive(bytes(password))

    nonce = os.urandom(16)

    cipher = Cipher(algorithms.AES(key),\
                    modes.CTR(nonce), backend=default_backend())
    enc = cipher.encryptor()
    ct = enc.update(data) + enc.finalize()

    #Add padding if needed
    ct += os.urandom(padding-16)

    #add nonce to data to allow decryption later (nonce does not need to be kept
    #secret and is indistinguishable from random noise)
    return bytes(nonce) + ct