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GnuPG creates ElGamal keys for signing using insufficient entropy

Vulnerability Note VU#940388

Original Release Date: 2003-12-29 | Last Revised: 2003-12-29

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.

Vendor Information

940388
 
Affected   Unknown   Unaffected

GNU Privacy Guard

Updated:  December 29, 2003

Status

  Vulnerable

Vendor Statement

No statement is currently available from the vendor regarding this vulnerability.

Vendor Information

The vendor has not provided us with any further information regarding this vulnerability.

Addendum

Please see the GnuPG advisory at http://lists.gnupg.org/pipermail/gnupg-announce/2003q4/000276.html

If you have feedback, comments, or additional information about this vulnerability, please send us email.


CVSS Metrics

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

References

Acknowledgements

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: CVE-2003-0971
Severity Metric: 6.33
Date Public: 2003-11-27
Date First Published: 2003-12-29
Date Last Updated: 2003-12-29 15:52 UTC
Document Revision: 7

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