GnuPG creates ElGamal keys for signing using insufficient entropy

2003-12-29T00:00:00
ID VU:940388
Type cert
Reporter CERT
Modified 2003-12-29T00:00:00

Description

Overview

Gnu Privacy Guard (GnuPG) is a cryptographic utility used to generate cryptographic keys and perform other cryptographic functions. A vulnerability in the way GnuPG generates ElGamal keys has been discovered. This vulnerability renders ElGamal signing key untrustworthy.

Description

A vulnerability in the algorithm to generate ElGamal sign+encrypt keys can permit an attacker to generate valid signatures without access to the private key. This vulnerability does not affect encrypt-only (type 16) ElGamal keys, only the ElGamal sign+encrypt key (type 20) when used to make a signature with a GnuPG version 1.0.2 or later.


Impact

A remote attacker can generate a valid signature without access to the private key.


Solution

Revoke your ElGamal signing keys. GnuPG has released a patch for version 1.2.3 or you can upgrade to version 1.2.4 or later.


Systems Affected

Vendor| Status| Date Notified| Date Updated
---|---|---|---
GNU Privacy Guard| | -| 29 Dec 2003
If you are a vendor and your product is affected, let us know.

CVSS Metrics

Group | Score | Vector
---|---|---
Base | N/A | N/A
Temporal | N/A | N/A
Environmental | N/A | N/A

References

  • <http://www.secunia.com/advisories/10304/>
  • <http://www.securityfocus.com/bid/9115>
  • <http://www.secunia.com/advisories/10349/>
  • <http://www.secunia.com/advisories/10400/>
  • <http://www.secunia.com/advisories/10399/>

Credit

Thanks to Werner Koch for his advisory on this issue, and Phong Nguyen for reporting this vulnerability.

This document was written by Jason A Rafail.

Other Information

  • CVE IDs: CAN-2003-0971
  • Date Public: 27 Nov 2003
  • Date First Published: 29 Dec 2003
  • Date Last Updated: 29 Dec 2003
  • Severity Metric: 6.33
  • Document Revision: 7