CryptoMOO

CryptoMOO is a simple Python library which implements cryptographic modes of operation.

API

The API is very simple and contains all the methods needed as follows:

• get_key() -> bytes - get a key in a safe manner
• set_key(key: bytes) -> None - set a key for encryption/decryption
• get_iv() -> bytes - get an IV in a safe manner
• get_ctr() -> bytes - get a counter in a safe manner
• inc_ctr(ctr: bytes) -> bytes - returns the given counter incremented
• set_mode(mode: Mode) -> None - mode of operation setup
• block_cipher_encrypt(data: bytes) -> bytes - encrypt a block
• block_cipher_decrypt(data: bytes) -> bytes - decrypt a block
• pad(data: bytes, pkcs7: bool) -> bytes - pad a block (including an empty block)
• unpad(data: bytes, pkcs7: bool) -> bytes - unpad a block (including an empty block)
• proccess_block_encrypt(data: bytes, is_final_block: bool, padding: str) -> bytes - add one block for encryption
  • This method is responsible for the main logic, mode branching happens here.
• process_block_decrypt(data: bytes, is_final_block: bool, padding: str) -> bytes - the same method, but for decryption
• encrypt(data: bytes, iv: bytes = None) -> bytes - encrypt data of arbitrary length
• decrypt(data: bytes, iv: bytes) -> bytes - decrypt data of arbitrary length

The methods that are most likely to be looked for in the first place are set_key, set_mode, encrypt and decrypt.

Sample decryption

The tests prove correctness of the primitives from the theoretical point of view.

To demonstrate how things work from the practical perspective, however, there is a separate program which decrypts the sample strings using the modes and the keys, all given in samples.txt

You can see the decrypted strings by running sample_dec.py or by looking directly at the results in samples_dec.txt