pyserpent 1.2.0

Pure Python implementation of the Serpent block cipher with CBC mode and PKCS#7 padding

pyserpent

[!CAUTION] Version 1.2.0 introduces a BREAKING CHANGE in CBC mode. The IV is now automatically prepended to the ciphertext. Data encrypted with v1.1.0 and earlier will not be compatible with the new decrypt function unless migrated. See below.

Install

pip install pyserpent

Quick Start - ECB

from pyserpent import Serpent

key = Serpent.generate_key()
serpent = Serpent(key)
plaintext = b"Hello, Serpent!!"

ciphertext = serpent.encrypt(plaintext)
decrypted = serpent.decrypt(ciphertext)

print(decrypted.decode())

Example Serpent CBC Mode

from pyserpent import Serpent, serpent_cbc_encrypt, serpent_cbc_decrypt

key = Serpent.generate_key()
plaintext = "Hello, Serpent!!"

# IV is generated automatically. To use your own: serpent_cbc_encrypt(key, plaintext, iv=your_iv)
ciphertext = serpent_cbc_encrypt(key, plaintext)
decrypted = serpent_cbc_decrypt(key, ciphertext)

print(decrypted.decode())

Migration from v1.1.0 to v1.2.0

To decrypt data created with version 1.1.0, you need to manually prepend the 16-byte IV to your ciphertext so the new version can recognize it.

If you used the default (zero) IV in v1.1.0:

# v1.1.0 used 16 zero bytes as default IV
old_iv = b'\x00' * 16
# Prepend it to your old ciphertext
prepared_ciphertext = old_iv + old_ciphertext

# Now it's compatible with v1.2.0 decrypt
plaintext = serpent_cbc_decrypt(key, prepared_ciphertext)

If you provided a custom IV in v1.1.0:

# Just prepend your IV to the ciphertext
prepared_ciphertext = your_old_iv + old_ciphertext
plaintext = serpent_cbc_decrypt(key, prepared_ciphertext)