cryptolib — cryptographic ciphers

The cryptolib module provides symmetric-cipher primitives. On OpenMV Cams it is included whenever the ssl module is enabled.

Classes

class cryptolib.aes(key: bytes | bytearray | memoryview, mode: int, IV: bytes | bytearray | memoryview | None = None)

Create a new AES cipher object, suitable for encryption or decryption. After initialisation, the cipher object can be used only for one direction — running decrypt() after encrypt() (or vice versa) is not supported.

Parameters:

  • key – the encryption/decryption key. Must be exactly 16 bytes (AES-128) or 32 bytes (AES-256); AES-192 is not supported. Any buffer-protocol object is accepted.

  • mode – selects the block-cipher mode:

    Value

    Name

    Description

    1

    ECB

    Electronic Code Book. Each 16-byte block is encrypted independently; identical plaintext blocks produce identical ciphertext. Generally not recommended for new designs.

    2

    CBC

    Cipher Block Chaining. Each block is XORed with the previous ciphertext block before encryption. Requires a 16-byte IV.

    ECB and CBC both require the input length to be a multiple of the 16-byte AES block size.

  • IV – the 16-byte initialisation vector for CBC mode. Ignored for ECB.

encrypt(in_buf: bytes | bytearray | memoryview, out_buf: bytearray | memoryview | None = None) → bytes

Encrypt in_buf. The buffer length must be a multiple of 16 bytes; pad the plaintext yourself before calling.

If out_buf is omitted the result is returned as a newly allocated bytes object. Otherwise the ciphertext is written into the mutable buffer out_buf, which must be at least as long as in_buf. in_buf and out_buf may refer to the same buffer for in-place encryption.

decrypt(in_buf: bytes | bytearray | memoryview, out_buf: bytearray | memoryview | None = None) → bytes

Like encrypt(), but reverses the operation.