aesio – AES encryption routines

The AES module contains classes used to implement encryption and decryption. It aims to be low overhead in terms of memory.

For more information on AES, refer to the Wikipedia entry.

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aesio.MODE_ECB: int
aesio.MODE_CBC: int
aesio.MODE_CTR: int
class aesio.AES(key: circuitpython_typing.ReadableBuffer, mode: int = 0, IV: circuitpython_typing.ReadableBuffer | None = None, segment_size: int = 8)

Encrypt and decrypt AES streams

Create a new AES state with the given key.

Parameters:

  • key (ReadableBuffer) – A 16-, 24-, or 32-byte key

  • mode (int) – AES mode to use. One of: MODE_ECB, MODE_CBC, or MODE_CTR

  • IV (ReadableBuffer) – Initialization vector to use for CBC or CTR mode

Additional arguments are supported for legacy reasons.

Encrypting a string:

import aesio
from binascii import hexlify

key = b'Sixteen byte key'
inp = b'CircuitPython!!!' # Note: 16-bytes long
outp = bytearray(len(inp))
cipher = aesio.AES(key, aesio.MODE_ECB)
cipher.encrypt_into(inp, outp)
hexlify(outp)
rekey(key: circuitpython_typing.ReadableBuffer, IV: circuitpython_typing.ReadableBuffer | None = None) → None

Update the AES state with the given key.

Parameters:

  • key (ReadableBuffer) – A 16-, 24-, or 32-byte key

  • IV (ReadableBuffer) – Initialization vector to use for CBC or CTR mode

encrypt_into(src: circuitpython_typing.ReadableBuffer, dest: circuitpython_typing.WriteableBuffer) → None

Encrypt the buffer from src into dest.

For ECB mode, the buffers must be 16 bytes long. For CBC mode, the buffers must be a multiple of 16 bytes, and must be equal length. For CTX mode, there are no restrictions.

decrypt_into(src: circuitpython_typing.ReadableBuffer, dest: circuitpython_typing.WriteableBuffer) → None

Decrypt the buffer from src into dest. For ECB mode, the buffers must be 16 bytes long. For CBC mode, the buffers must be a multiple of 16 bytes, and must be equal length. For CTX mode, there are no restrictions.