USN-1484-1: PyCrypto vulnerability

Ubuntu Security Notice USN-1484-1

28th June, 2012

python-crypto vulnerability

A security issue affects these releases of Ubuntu and its derivatives:

  • Ubuntu 12.04 LTS
  • Ubuntu 11.10
  • Ubuntu 11.04
  • Ubuntu 10.04 LTS


PyCrypto improperly created ElGamal encryption keys.

Software description

  • python-crypto - cryptographic algorithms and protocols for Python


It was discovered that PyCrypto produced inappropriate prime numbers when
generating ElGamal keys. An attacker could use this flaw to facilitate
brute-forcing of ElGamal encryption keys.

Update instructions

The problem can be corrected by updating your system to the following package version:

Ubuntu 12.04 LTS:
python-crypto 2.4.1-1ubuntu0.1
Ubuntu 11.10:
python-crypto 2.3-2ubuntu0.1
Ubuntu 11.04:
python-crypto 2.1.0-2ubuntu1.1
Ubuntu 10.04 LTS:
python-crypto 2.0.1+dfsg1-4ubuntu2.2

To update your system, please follow these instructions:

In general, a standard system update will make all the necessary changes.
If PyCrypto was used to generate ElGamal keys, we recommend they be