Cannot encrypt with RSA in python 3.3

[Chris Lamb]

Hi everyone, I can't encrypt a message using RSA in python 3.3. Python 3.3 virtualenv with pyCrypto:

(pyCrypto-3.3) s946259:pyCrypto cclamb$ python test.py
Traceback (most recent call last):
  File "test.py", line 9, in <module>
    ciphertext = cipher.encrypt(message)
  File "/Users/cclamb/PycharmProjects/interpreters/pyCrypto-3.3/lib/python3.3/site-packages/Crypto/Cipher/PKCS1_OAEP.py", line 150, in encrypt
    db = lHash + ps + bchr(0x01) + message
TypeError: can't concat bytes to str

Python 2.7 virtualenv with pyCrypto:

(pyCrypto-2.7) s946259:pyCrypto cclamb$ python test.py
??םB??;?
??q??ڠ??s?o6???{ٍyT?B?qb?o??
                           ??fp?AC?]C?|???j? ?s??.
                                                     ?r????(?@_?6?5A[??"???6:?HX??da,q?;?"??爝F?W?8?iG
                                                                                                       ՚?? JH???u??
                                                                                                                   x??Z?t??ok?$?a???Ym??S?b?M͈w?/???? ?~T??/@?/??9?B?'???'p??m???>???.?O??ndS?~????Q,?308???y

Here's the contents of test.py:

from Crypto.PublicKey import RSA
from Crypto import Random
from Crypto.Cipher import PKCS1_OAEP

rng = Random.new().read
message = 'To be encrypted'
key = RSA.generate(2048, rng)
cipher = PKCS1_OAEP.new(key)
ciphertext = cipher.encrypt(message)

print(ciphertext)

[Legrandin (gooksankoo)]

The line:

message = 'To be encrypted'

should be:

message = b'To be encrypted'

In Python 3, strings are not encoded and therefore cannot be encrypted (unless one silently performs some arbitrary encoding like Latin 1). In Python 2, strings and encoded strings (that is, a "bytes" object) were mixed and your example would have worked.

See here:

http://eli.thegreenplace.net/2012/01/30/the-bytesstr-dichotomy-in-python-3/

[Chris Lamb (chrislambistan)]

Ah! Thanks! We may have a documentation bug then, I followed a couple of
examples in the API docs. I will look at fixing and documenting and will
update this ticket with results.

On Tuesday, May 7, 2013, Legrandin <email address hidden> wrote:

> The line:
>
> message = 'To be encrypted'
>
> should be:
>
> message = b'To be encrypted'
>
> In Python 3, strings are not encoded and therefore cannot be encrypted
> (unless one silently performs some arbitrary encoding like Latin 1). In
> Python 2, strings and encoded strings (that is, a "bytes" object) were
> mixed and your example would have worked.
>
> See here:
>
> http://eli.thegreenplace.net/2012/01/30/the-bytesstr-dichotomy-in-
> python-3/
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1177614
>
> Title:
> Cannot encrypt with RSA in python 3.3
>
> Status in Python Cryptography Toolkit:
> New
>
> Bug description:
> Hi everyone, I can't encrypt a message using RSA in python 3.3.
> Python 3.3 virtualenv with pyCrypto:
>
> (pyCrypto-3.3) s946259:pyCrypto cclamb$ python test.py
> Traceback (most recent call last):
> File "test.py", line 9, in <module>
> ciphertext = cipher.encrypt(message)
> File
> "/Users/cclamb/PycharmProjects/interpreters/pyCrypto-3.3/lib/python3.3/site-packages/Crypto/Cipher/PKCS1_OAEP.py",
> line 150, in encrypt
> db = lHash + ps + bchr(0x01) + message
> TypeError: can't concat bytes to str
>
> Python 2.7 virtualenv with pyCrypto:
>
> (pyCrypto-2.7) s946259:pyCrypto cclamb$ python test.py
> ??םB??;?
> ??q??ڠ??s?o6???{ٍyT?B?qb?o??
> ??fp?AC?]C?|???j? ?s??.
>
> ?r????(?@_?6?5A[??"???6:?HX??da,q?;?"??爝F?W?8?iG
>
> ՚?? JH???u??
>
>
> x??Z?t??ok?$?a???Ym??S?b?M͈w?/????
> ?~T??/@?/??9?B?'???'p??m???>???.?O??ndS?~????Q,?308???y
>
> Here's the contents of test.py:
>
> from Crypto.PublicKey import RSA
> from Crypto import Random
> from Crypto.Cipher import PKCS1_OAEP
>
> rng = Random.new().read
> message = 'To be encrypted'
> key = RSA.generate(2048, rng)
> cipher = PKCS1_OAEP.new(key)
> ciphertext = cipher.encrypt(message)
>
> print(ciphertext)
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/pycrypto/+bug/1177614/+subscriptions
>

[Legrandin (gooksankoo)]

Indeed it is a documentation bug.

FYI, I also created a fix here:

https://github.com/Legrandin/pycrypto/commit/09093410799d8e859ce570dd947b35c444931fbc

[Darsey Litzenberger (dlitz)]

Pull request: https://github.com/dlitz/pycrypto/pull/43

Fix committed to master: https://github.com/dlitz/pycrypto/commit/74bd74f490f4eadbfa9a3d750645b21e46679317