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What is the practical strength of DSA1024/Elgamal2048 (former GnuPG default)?
Hello,
until about 2009 GnuPG [1] had dsa1024/elg2048 as default key algorithms.
There are still keys around with those algorithmus.

Recommendations from the US and Europe [2] only list DSA between 1900
and 3000 bits as allowed for legacy use. So it is clear that DSA1024
should not be used anymore.

How urgent is it to convince people to create new keypairs?
To me this means rephrased:
How strong or weak is this combination of keys for todays usage?

Wikipedia points out a strong sensitivity of the algorithm to the quality of
random number generators and that implementations could deliberately leak
information in the signature [3]. This alone probably is a reason to switch
keys.

Apart from the problems an attacker could be solving the discrete log problem.
A presentation from 2013 [4] assumes that advances are made towards solving
this in a practical time frame. Does somebody has good pointers on the state
of the art for this?

Because dsa1024/elg2048 used to be a default of GnuPG, I think it would be
helpful to point our users towards a well understood reasoning when and why
they should move to a better key-pair.

What do you think?

Best Regards,
Bernhard

[1] https://lists.gnupg.org/pipermail/gnupg-devel/2009-May/025079.html
[2]
https://www.sogis.eu/documents/cc/crypto/SOGIS-Agreed-Cryptographic-Mechanisms-1.1.pdf
https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-57pt1r4.pdf#page=66

[3]
https://en.wikipedia.org/wiki/Digital_Signature_Algorithm#Sensitivity

[4]
https://isecpartners.com/media/105564/ritter_samuel_stamos_bh_2013_cryptopocalypse.pdf
--
www.intevation.de/~bernhard ? +49 541 33 508 3-3
Intevation GmbH, Osnabr?ck, DE; Amtsgericht Osnabr?ck, HRB 18998
Gesch?ftsf?hrer Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
Re: What is the practical strength of DSA1024/Elgamal2048 (former GnuPG default)? [ In reply to ]
On 4/25/19 9:20 AM, Bernhard Reiter wrote:
> Wikipedia points out a strong sensitivity of the algorithm to the quality of
> random number generators and that implementations could deliberately leak
> information in the signature [3]. This alone probably is a reason to switch
> keys.

This isn't really a major point given rfc6979 (
https://tools.ietf.org/html/rfc6979 ): Deterministic Usage of the
Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature
Algorithm (ECDSA)


--
----------------------------
Kristian Fiskerstrand
Blog: https://blog.sumptuouscapital.com
Twitter: @krifisk
----------------------------
Public OpenPGP keyblock at hkp://pool.sks-keyservers.net
fpr:94CB AFDD 3034 5109 5618 35AA 0B7F 8B60 E3ED FAE3
----------------------------
Corruptissima re publica plurimæ leges
The greater the degeneration of the republic, the more of its laws
Re: What is the practical strength of DSA1024/Elgamal2048 (former GnuPG default)? [ In reply to ]
On Thu, Apr 25, 2019 at 11:19:15AM +0200, Kristian Fiskerstrand wrote:
> On 4/25/19 9:20 AM, Bernhard Reiter wrote:
> > Wikipedia points out a strong sensitivity of the algorithm to the quality of
> > random number generators and that implementations could deliberately leak
> > information in the signature [3]. This alone probably is a reason to switch
> > keys.
>
> This isn't really a major point given rfc6979 (
> https://tools.ietf.org/html/rfc6979 ): Deterministic Usage of the
> Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature
> Algorithm (ECDSA)
>

Does GnuPG use deterministic DSA / ECDSA?
Re: What is the practical strength of DSA1024/Elgamal2048 (former GnuPG default)? [ In reply to ]
On 30.08.2019 01:02, Brian Minton wrote:
> On Thu, Apr 25, 2019 at 11:19:15AM +0200, Kristian Fiskerstrand wrote:
>> On 4/25/19 9:20 AM, Bernhard Reiter wrote:
>>> Wikipedia points out a strong sensitivity of the algorithm to the quality of
>>> random number generators and that implementations could deliberately leak
>>> information in the signature [3]. This alone probably is a reason to switch
>>> keys.
>> This isn't really a major point given rfc6979 (
>> https://tools.ietf.org/html/rfc6979 ): Deterministic Usage of the
>> Digital Signature Algorithm (DSA) and Elliptic Curve Digital Signature
>> Algorithm (ECDSA)
>>
> Does GnuPG use deterministic DSA / ECDSA?
>

Yes (at least for modern versions, iirc it was introduced in libgcrypt
1.6.0, but it has been used for 6 or so years)

--
----------------------------
Kristian Fiskerstrand
Blog: https://blog.sumptuouscapital.com
Twitter: @krifisk
----------------------------
Public OpenPGP keyblock at hkp://pool.sks-keyservers.net
fpr:94CB AFDD 3034 5109 5618 35AA 0B7F 8B60 E3ED FAE3
----------------------------
Corruptissima re publica plurimæ leges
The greater the degeneration of the republic, the more of its laws