It seems too late to reject on import, given that people might already have such a secret key in their ~/.gnupg/private-keys-v1.d/ They might have had it for years without knowing it, because the failure is so intermittent. They might just think that they did something wrong, and when they try again it works. It would be great to be more robust than that.

In more than 25 years of OpenPGP we only had a few new implementations which got it wrong. I see no need to fix it here - maybe import could indeed reject such a key, though.

Maybe there's a 4th possible option that's better than the three i identified?

So i see a range of ways that any OpenPGP software could deal with this:

I can replicate that and it works if you disable the use of the CRT. Looking at the key:

pkey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
 pkey[1]: 010001
 skey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
 skey[3]: F57D9F597750967DF272D9AC661DDC212D7C5CA4C6E91573A80756281351CDC3A2532B155D9251029F89A0A0807DF2BD177DC30FC6A847E07738B55606DF032ADAD8361E0AFEE9C0CF7D566793834977FAAE9C4B87132B94F665EFF463777CDE7EB89113FA3AAC194B6F2D30C40BE7C0DDE36A5855277C1E4D0204FC4C737BCB
 skey[4]: C4B135296B8F4390B953DDA84249FC8467CFF81FC715D1B5F3E01FCC8DC770813630AEA93982F2004705C4D272E07A10B1882AC5C09A45E88B14A1446B4C639B549420CE3BF90947E6E86503E426A8FDAC4C5CFC2809F5F0A1647ED5EE2457C054A40AA1F0666B28B2C970BE2093AE7B095A688B2D713CA8885826F23AFB37D9
 skey[5]: 0790A8E260C6CADC353FB3961D798EFD4F15F96752DA20B86841334C38861743DD7A1FEB2B750D0864F5901BE541B6C8FB63649B18FDC4A32A1233EF90872DCD35704A4B4063DB62752CF6A7FD00F086C6B1042A2B0CB6FB36B7D5269671DACF55242A838E60D514BA868354910CEB1C41FB9A43BF932B5036A6EFE35236FFC7

Most things are done. Missing stuff

Alright: We have support for all our combined algos ky{768,1024}_bp{256,384,512}and ky{768,1024}_cv{25519,448} as well as test keys and encrypted test messages.

What is the current status of this issue?

Here comes a new test key along with its 3 secret parts (one for the primary and two for the composite Kyber subkey).

Wit the test keys posted in T7014 it is now possible to decrypt the sample data. The test data has been slightly adjusted for the new format; see

See also: https://gnupg.org/blog/20240125-smartcard-backup-key.html

Also fixed in the fortgcoming 2.2.43

Fixed in 2.4.4. Feel free to re-open if you still see problems.

Fixed in 2.4.4 and 2.2.43 - see above for affected versions.

We need to fix 2.2.42 too. This because we backported the responsible patch.

We tested with Kleopatra:

• Only gpg4win 4.2 is affected (the current version) but 4.1 is not affected.
• No vsd version is affected.

FWIW, I am already working on this.

Currently, there is no support for gpg-agent to keep private key not on disk, but only on memory of gpg-agent. Given the situation,
I think that it is good to:

Way to late for a change and also adding another algorithm (SIV) complicates things for no good purposes.

I applied your patch and also fixed another possible problem.

It's true that for KEYTOCARD command, there is optional argument for ECDH.
My point is that for PKDECRYPT command, it will be needed to add mechanism for getting such a parameter (when we use KEM API in gpg-agent).

We already have the ECDH parameters for OpenPGP in the gpg-agent API. The question is how large the data for PQC will be - likely we need to use an inquire already for this reason.

Considering the design of gpg-agent which focuses on private key operations and data, it would be better to enhance the gpg-agent protocol to inquire public key data of any format defined by the client (including ECDH KDF parameters of OpenPGP). I mean, instead of storing data in the key file (originally designed for private key + some additional data), we will enhance the protocol.

Further investigation showed that this was due to a bogus key creating during I wrote the code.

Will be in 2.4.4. GPGME 1.23.0 with support has been released.