3. Upgrading from older versions

3.1. From versions older than Python-RSA 4.0

Support for the VARBLOCK/bigfile format has been dropped in version 4.0, after being deprecated for a year. There is no alternative implementation in Python-RSA 4.0. If you need this, or have ideas on how to do handle encryption of large files securely and in a compatible way with existing standards, open a ticket to discuss this.

3.2. From versions older than Python-RSA 3.4

Previous versions of Python-RSA were less secure than the current version. In order to be able to gradually upgrade your software, those old versions will be available until Python-RSA 4.0.

To use version 1.3.3, use this:

import rsa._version133 as rsa

And to use version 2.0, use this:

import rsa._version200 as rsa

You can import all three versions at the same time. This allows you to use an old version to decrypt your messages, and a new version to re-encrypt them:

import rsa._version200 as rsa200
import rsa                        # this imports version 3.0

decrypted = rsa200.decrypt(old_crypto, version_200_private_key)
new_crypto = rsa.encrypt(decrypted, version_3_public_key)

Those import statements will create warnings as they import much less secure code into your project.


These modules are included to allow upgrading to the latest version of Python-RSA, and not as a way to keep using those old versions. They will be removed in version 4.0.

The random padding introduced in version 3.0 made things much more secure, but also requires a larger key to encrypt the same message.

3.3. Converting keys

Version 3.0 introduced industrial standard RSA keys according to PKCS#1. The old keys were just dictionaries. To convert a key from an older version of Python-RSA, use the following:

import rsa

# Load the old key somehow.
old_pub_key = {
    'e': 65537,
    'n': 31698122414741849421263704398157795847591L

old_priv_key = {
    'd': 7506520894712811128876594754922157377793L,
    'p': 4169414332984308880603L,
    'q': 7602535963858869797L

# Create new key objects like this:
pub_key = rsa.PublicKey(n=old_pub_key['n'], e=old_pub_key['e'])

priv_key = rsa.PrivateKey(n=old_pub_key['n'], e=old_pub_key['e'],
    d=old_priv_key['d'], p=old_priv_key['p'], q=old_priv_key['q'])

# Or use this shorter notation:
pub_key = rsa.PublicKey(**old_pub_key)

priv_key = rsa.PrivateKey(**old_priv_key)