PyCrypto v2.7a1 Release Notes

Release Date: 2013-10-21 // about 8 years ago

Previous changes from v2.6.1

  • * [CVE-2013-1445] Fix PRNG not correctly reseeded in some situations.
      In previous versions of PyCrypto, the Crypto.Random PRNG exhibits a
      race condition that may cause forked processes to generate identical
      sequences of 'random' numbers.
      This is a fairly obscure bug that will (hopefully) not affect many
      applications, but the failure scenario is pretty bad.  Here is some
      sample code that illustrates the problem:
          from binascii import hexlify
          import multiprocessing, pprint, time
          import Crypto.Random
          def task_main(arg):
              a = Crypto.Random.get_random_bytes(8)
              b = Crypto.Random.get_random_bytes(8)
              rdy, ack = arg
              return "%s,%s" % (hexlify(a).decode(),
          n_procs = 4
          manager = multiprocessing.Manager()
          rdys = [manager.Event() for i in range(n_procs)]
          acks = [manager.Event() for i in range(n_procs)]
          pool = multiprocessing.Pool(processes=n_procs,
          res_async = pool.map_async(task_main, zip(rdys, acks))
          [rdy.wait() for rdy in rdys]
          [ack.set() for ack in acks]
          res = res_async.get()
      The output should be random, but it looked like this:
      This release fixes the problem by resetting the rate-limiter when
      Crypto.Random.atfork() is invoked.  It also adds some tests and a
      few related comments.


    * [CVE-2012-2417] Fix LP#985164: insecure ElGamal key generation.
      (thanks: Legrandin)
      In the ElGamal schemes (for both encryption and signatures), g is
      supposed to be the generator of the entire Z^*_p group.  However, in
      PyCrypto 2.5 and earlier, g is more simply the generator of a random
      sub-group of Z^*_p.
      The result is that the signature space (when the key is used for
      signing) or the public key space (when the key is used for encryption)
      may be greatly reduced from its expected size of log(p) bits, possibly
      down to 1 bit (the worst case if the order of g is 2).
      While it has not been confirmed, it has also been suggested that an
      attacker might be able to use this fact to determine the private key.
      Anyone using ElGamal keys should generate new keys as soon as practical.
      Any additional information about this bug will be tracked at
    * Huge documentation cleanup (thanks: Legrandin).
    * Added more tests, including test vectors from NIST 800-38A
      (thanks: Legrandin)
    * Remove broken MODE_PGP, which never actually worked properly.
      A new mode, MODE_OPENPGP, has been added for people wishing to write
      OpenPGP implementations.  Note that this does not implement the full
      OpenPGP specification, only the "OpenPGP CFB mode" part of that
    * Fix: getPrime with invalid input causes Python to abort with fatal error
    * Fix: Segfaults within error-handling paths
      (thanks: Paul Howarth & Dave Malcolm)
    * Fix: Block ciphers allow empty string as IV
    * Fix DevURandomRNG to work with Python3's new I/O stack.
      (thanks: Sebastian Ramacher)
    * Remove automagic dependencies on libgmp and libmpir, let the caller
      disable them using args.
    * Many other minor bug fixes and improvements (mostly thanks to Legrandin)


    * Added PKCS#1 encryption schemes (v1.5 and OAEP).  We now have
      a decent, easy-to-use non-textbook RSA implementation.  Yay!
    * Added PKCS#1 signature schemes (v1.5 and PSS). v1.5 required some
      extensive changes to Hash modules to contain the algorithm specific
      ASN.1 OID. To that end, we now always have a (thin) Python module to
      hide the one in pure C.
    * Added 2 standard Key Derivation Functions (PBKDF1 and PBKDF2).
    * Added export/import of RSA keys in OpenSSH and PKCS#8 formats.
    * Added password-protected export/import of RSA keys (one old method
      for PKCS#8 PEM only).
    * Added ability to generate RSA key pairs with configurable public
      exponent e.
    * Added ability to construct an RSA key pair even if only the private
      exponent d is known, and not p and q.
    * Added SHA-2 C source code (fully from Lorenz Quack).
    * Unit tests for all the above.
    * Updates to documentation (both inline and in Doc/pycrypt.rst)
    * All of the above changes were put together by Legrandin (Thanks!)
    * Minor bug fixes ( and tests).