LightDSA

Common errors

• ModuleNotFoundError: No module named 'Crypto'

  cause The `lightdsa` library uses `pycryptodome` internally, which often exposes its modules under the `Crypto` namespace. This error indicates `pycryptodome` is not installed.
  fix Install the `pycryptodome` package: `pip install pycryptodome`.

• TypeError: object of type 'str' has no len()

  cause Cryptographic functions for signing and verification expect byte-like objects (e.g., `bytes`), not strings. You are likely passing a Python `str` directly.
  fix Convert your string data to bytes before passing it to `sign()` or `verify()`. For example, `my_string.encode('utf-8')`.

Warnings

• gotcha The LightDSA library appears to be unmaintained. The last commit on GitHub was in 2021, and the version 0.0.3 suggests early development. Users should be aware that it may not receive future updates or security fixes.
  Fix: Consider alternatives for actively maintained cryptographic libraries in production environments, such as `cryptography`.
• gotcha Despite its name, LightDSA currently only supports the RSA algorithm for digital signatures. The `key_size` parameter is specifically for RSA key lengths.
  Fix: Do not expect support for other DSA algorithms like ECDSA. If you require other signature types, use a more comprehensive library like `cryptography`.
• gotcha LightDSA relies on the `pycryptodome` library. Incorrect or incomplete installation of `pycryptodome` (which might require C build tools on some systems) can lead to runtime errors.
  Fix: Ensure `pycryptodome` is correctly installed: `pip install pycryptodome`. If you encounter build errors, consult `pycryptodome`'s documentation for platform-specific dependencies.

Install

• pip install lightdsa Install LightDSA

Imports

• LightDSA

  from lightdsa import LightDSA

Quickstart

This quickstart demonstrates how to generate RSA keys, sign a message, and verify the signature using the `LightDSA` class. It also shows how to load keys from PEM format.

from lightdsa import LightDSA

# 1. Generate keys
# For RSA, key_size must be between 1024 and 4096 (inclusive)
# and a multiple of 256.
dsa = LightDSA(key_size=2048) # Default is 2048
private_key_pem = dsa.private_key_to_pem().decode('utf-8')
public_key_pem = dsa.public_key_to_pem().decode('utf-8')

print("Private Key (PEM format):")
print(private_key_pem)
print("\nPublic Key (PEM format):")
print(public_key_pem)

# 2. Sign data
message_to_sign = "This is a secret message."
signature = dsa.sign(message_to_sign.encode('utf-8'))

print(f"\nMessage: {message_to_sign}")
print(f"Signature: {signature.hex()}")

# 3. Verify signature using the current object's keys
is_valid = dsa.verify(message_to_sign.encode('utf-8'), signature)
print(f"Signature valid: {is_valid}")

# You can also load keys from PEM strings into a new LightDSA instance
dsa_loaded = LightDSA(key_size=2048) # key_size required for initialization
dsa_loaded.load_public_key_from_pem(public_key_pem.encode('utf-8'))
dsa_loaded.load_private_key_from_pem(private_key_pem.encode('utf-8')) # Optional for verification

is_valid_loaded = dsa_loaded.verify(message_to_sign.encode('utf-8'), signature)
print(f"Signature valid (loaded keys): {is_valid_loaded}")