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GnuPG ElGamal Signing Weakness Expose Private Key
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Secunia Advisory:
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SA10304
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Release Date:
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2003-11-27
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Last Update:
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2003-12-29
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Popularity:
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10,997 views
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Critical:
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Moderately critical
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Impact:
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Spoofing
Exposure of sensitive information
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Where:
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From remote
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Solution Status:
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Vendor Patch
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| Software: | GnuPG / gpg 1.0.x
GnuPG / gpg 1.2.x
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| CVE reference: | CVE-2003-0971
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Description:
A weakness has been identified in the handling of ElGamal keys in GnuPG, which exposes the private key.
The problem is a that certain versions of GnuPG creates ElGamal sign+encrypt keys (type 20) in a cryptographically weak way. This can be exploited to derive the private key.
In an advisory from the developers of GnuPG, it is stated that all ElGamal type 20 keys should be considered compromised.
This affects ElGamal type 20 keys generated with GnuPG 1.0.2 to 1.2.3.
ElGamal encrypt-only keys (type 16) are not affected.
Further details are available in the original advisory.
Solution:
Future versions of GnuPG will not include support for ElGamal type 20 keys.
Patch for GnuPG 1.2.3, which will remove the support for ElGamal type 20 keys:
http://lists.gnupg.org/pipermail/gnupg-users/2003-November/020771.html
Provided and/or discovered by:
Phong Nguyen
Changelog:
2003-12-04: Added CVE reference.
2003-12-29: Added link to CERT.
Original Advisory:
http://lists.gnupg.org/pipermail/gnupg-users/2003-November/020772.html
Other References:
CERT VU#940388:
http://www.kb.cert.org/vuls/id/940388
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Please note: The information that this Secunia Advisory is based on comes from a third party unless stated otherwise.
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