Keys produced non-interactively with PGP v5.0 on a system with a /dev/random device may be predictable, especially those produced in an environment without a pre-existing randseed.bin file.
Documents encrypted with a vulnerable key may recoverable by an attacker. Additionally, an attacker may be able to forge a digital signature corresponding to a vulnerable key.
Signatures produced using a vulnerable key, including signatures in certificates, may be untrustworthy.
If your PGP key was generated non-interactively using any version of PGP v5.0 on a system with a /dev/random device, you may wish to revoke it.
Documents encrypted with a predictable key may need to be re-encrypted with a non-vulnerable key, if your particular circumstances warrant it; that is, if the information still needs to be encrypted.
You may need to resign documents signed with a vulnerable key if your circumstances warrant it.
Appendix A Vendor Information
Network Associates Security Advisory
Date: May 30, 2000
Author: PGP Engineering
A security issue has been discovered in the following PGP products:
- PGP 5.0 for Linux, US Commercial and Freeware editions
- PGP 5.0 for Linux, Source code book (basis for PGP 5.0i for Linux)
The following PGP products are NOT affected by this issue:
- PGP 1.x products
- PGP 2.x products
- PGP 4.x products
- All other PGP 5.x products
- PGP 6.x products
- PGP 7.x products
During a recent review of our published PGP 5.0 for Linux source code, researchers discovered that under specific, rare circumstances PGP 5.0 for Linux will generate weak, predictable public/private keypairs. These keys can only be created under the
- Keys are generated using PGP's command line option for unattended batch key generation, with no user interaction for entropy (random data) collection
- No keys were generated interactively on this system previously (e.g., a PGP random seed file is not present on this system prior to unattended batch key generation)
- PGP is able to access the UNIX /dev/random service to gather entropy during unattended batch key generation
PGP 5.0 for Linux does not process the data read from /dev/random appropriately, and therefore does not gather enough entropy required to generate strong public/private keypairs. This issue affects both RSA and Diffie-Hellman public/private keypairs,
regardless of keysize. Network Associates has verified that this issue does not exist in any other version of PGP.
Users who generated keys in the manner described above are strongly urged to do the following:
- Revoke and no longer use keys suspected to have this problem
- Generate new public/private keypairs with entropy collected from users' typing and/or mouse movements
- Re-encrypt any data with the newly generated keypairs that is currently encrypted with keys suspected to have this problem
- Re-sign any data with the newly generated keypairs, if required
Users are also urged to upgrade to the latest releases of PGP, as PGP 5.0 products have not been officially supported by Network Associates since early 1999, or distributed by Network Associates since June 1998.
US commercial and freeware versions of PGP 5.0 for Linux were released in September 1997 by PGP, Inc., a company founded by Phil Zimmermann. Source code for the PGP 5.0 product family was published in September 1997. PGP, Inc. was acquired by Network
Associates in December 1997.
PGP appreciates the efforts of Germano Caronni, Thomas Roessler and Marcel Waldvogel in identifying this issue and bringing it to our attention.
A pgp signed version of this statement is also available at
The CERT Coordination Center thanks Germano Caronni, Thomas Roessler, and Marcel Waldvogel for initially discovering and reporting this vulnerability, and for their help in developing this advisory. Additionally we thank Brett Thomas for his
Shawn Hernan was the primary author of this document.
Copyright 2000 Carnegie Mellon University.
May 30, 2000: initial release