1.1 Ucryptolib Module API Manual

1. Overview

The Ucryptolib library provides the following encryption and decryption functionalities: AES-ECB, AES-CBC, AES-CTR, AES-GCM, and SM4. Among these, AES-ECB, AES-CBC, and AES-CTR modes are natively implemented by MicroPython’s software library, while AES-GCM and SM4 are accelerated through underlying hardware accelerators.

Note: This document does not detail the encryption and decryption steps for AES-ECB, AES-CBC, and AES-CTR modes. For related information, please refer to MicroPython’s official cryptolib documentation.

2. API Introduction

The Ucryptolib library provides two main classes: aes and sm4, which implement encryption (encrypt) and decryption (decrypt) operations respectively.

2.1 Class aes

Description

The aes class is used to initialize an AES-GCM encryption/decryption object, supporting encryption and decryption operations. In the AES-GCM encryption/decryption algorithm, you must specify the key (key), mode (mode), initialization vector (IV), and additional authenticated data (AAD) during initialization.

Note: Once initialized, the encryption or decryption object can only be used for a single operation, either encryption or decryption, and cannot be used for both simultaneously.

Syntax

ucryptolib.aes((key, mode, IV, AAD))

Parameters

Parameter Name	Description	Input/Output
key	Encryption/decryption key, supports a key length of 256 bits	Input
mode	Encryption/decryption mode, supported mode is AES-GCM, set mode=0	Input
IV	Initialization vector, length of 12 bytes	Input
AAD	Additional authenticated data for data integrity verification, supports any length	Input

Example

import ucryptolib

# Initialize AES-GCM object
cipher = ucryptolib.aes(key, mode=0, IV=iv, AAD=aad)

# Perform encryption operation
ciphertext = cipher.encrypt(plaintext)

# Perform decryption operation
decrypted_text = cipher.decrypt(ciphertext)

2.2 Class sm4

Description

The sm4 class is used to initialize an SM4 encryption/decryption object, supporting encryption and decryption operations according to the Chinese national cryptographic standard SM4. Similar to AES-GCM, SM4 requires a key (key), mode (mode), and initialization vector (IV) during initialization.

Syntax

ucryptolib.sm4((key, mode, IV))

Parameters

Parameter Name	Description	Input/Output
key	SM4 encryption/decryption key, supports a key length of 128 bits	Input
mode	Encryption/decryption mode, supports ECB (Electronic Codebook) and CBC (Cipher Block Chaining) modes	Input
IV	Initialization vector, length of 16 bytes, must be provided in CBC mode	Input

Example

import ucryptolib

# Initialize SM4 object
cipher = ucryptolib.sm4(key, mode=1, IV=iv)

# Perform encryption operation
ciphertext = cipher.encrypt(plaintext)

# Perform decryption operation
decrypted_text = cipher.decrypt(ciphertext)