source_utils.py 文件源码

def evpKDF(passwd, salt, key_size=8, iv_size=4, iterations=1, hash_algorithm="md5"):
    target_key_size = key_size + iv_size
    derived_bytes = ""
    number_of_derived_words = 0
    block = None
    hasher = hashlib.new(hash_algorithm)
    while number_of_derived_words < target_key_size:
        if block is not None:
            hasher.update(block)

        hasher.update(passwd)
        hasher.update(salt)
        block = hasher.digest()
        hasher = hashlib.new(hash_algorithm)

        for _i in range(1, iterations):
            hasher.update(block)
            block = hasher.digest()
            hasher = hashlib.new(hash_algorithm)

        derived_bytes += block[0: min(len(block), (target_key_size - number_of_derived_words) * 4)]

        number_of_derived_words += len(block) / 4

    return {
        "key": derived_bytes[0: key_size * 4],
        "iv": derived_bytes[key_size * 4:]
    }