CODEWITHSUNDEEP
pythonopensslrsaencryption
Jonathan Holloway
Jonathan Holloway

Reputation: 63734

Python RSA Decryption Using OpenSSL Generated Keys

Does anyone know the simplest way to import an OpenSSL RSA private/public key (using a passphrase) with a Python library and use it to decrypt a message.

I've taken a look at ezPyCrypto, but can't seem to get it to recognise an OpenSSL RSA key, I've tried importing a key with importKey as follows:

key.importKey(myKey, passphrase='PASSPHRASE')

myKey in my case is an OpenSSL RSA public/private keypair represented as a string.

This balks with:

unbound method importKey() must be called with key instance as first argument (got str instance instead)

The API doc says:

importKey(self, keystring, **kwds)

Can somebody suggest how I read a key in using ezPyCrypto? I've also tried:

key(key, passphrase='PASSPHRASE')

but this balks with:

ezPyCrypto.CryptoKeyError: Attempted to import invalid key, or passphrase is bad

Link to docs here:

http://www.freenet.org.nz/ezPyCrypto/detail/index.html

EDIT: Just an update on this. Successfully imported an RSA key, but had real problem decrypting because eqPyCrypto doesn't support the AES block cipher. Just so that people know. I successfully managed to do what I wanted using ncrypt (http://tachyon.in/ncrypt/). I had some compilation issues with M2Crypto because of SWIG and OpenSSL compilation problems, despite having versions installed that exceeded the minimum requirements. It would seem that the Python encryption/decryption frameworks are a bit of a minefield at the moment. Ho hum, thanks for your help.

Upvotes: 4

Views: 11629

Answers (2)

abbot
abbot

Reputation: 27890

It is not clear what are you trying to achieve, but you could give M2Crypto a try. From my point of view it is the best OpenSSL wrapper available for Python.

Here is a sample RSA encryption/decription code:

import M2Crypto as m2c
import textwrap
key = m2c.RSA.load_key('key.pem', lambda prompt: 'mypassword')

# encrypt something:
data = 'testing 123'
encrypted = key.public_encrypt(data, m2c.RSA.pkcs1_padding)
print "Encrypted data:"
print "\n".join(textwrap.wrap(' '.join(['%02x' % ord(b) for b in encrypted ])))

# and now decrypt it:
decrypted = key.private_decrypt(encrypted, m2c.RSA.pkcs1_padding)
print "Decrypted data:"
print decrypted
print data == decrypted

Upvotes: 5

ephemient
ephemient

Reputation: 204974

The first error is telling you that importKey needs to be called on an instance of key.

k = key()
k.importKey(myKey, passphrase='PASSPHRASE')

However, the documentation seems to suggest that this is a better way of doing what you want:

k = key(keyobj=myKey, passphrase='PASSPHRASE')

Upvotes: 6

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