Adding post-quantum cryptography (PQC) support

[junaruga]

This ticket is a sub task of the https://bugs.ruby-lang.org/issues/22068.

For the common topics which is not RubyGems specific, you can check this Ruby issue ticket. I write drb related things on this ticket.

DRb::DRbSSLSocket::SSLConfig already works with pre-generated PQC-supported ML-DSA cert/key by :SSLCertificate and :SSLPrivateKey config options.

However, drbssl server's dual/multiple certificate support are missing. An SSL server that accepts clients with either ML-DSA-NN or RSA certificates is useful in the use case of PQC migration from RSA (non-PQC) to ML-DSA (PQC). I also want DRb::DRbSSLSocket::SSLConfig#setup_certificate's option to generate ML-DSA-44, ML-DSA-65, ML-DSA-87 certificates and keys. I prepared the PR. I am going to send the PR soon.

Files to modify

Below is a list of the files that we may modify to support PQC at least.

lib/drb/ssl.rb

PQC related pull-requests

• Add post-quantum cryptography (PQC) support to SSLConfig #53

[junaruga]

I sent the PR #53. As far as I know, after merging the PR, We can complete PQC support for drb, and close this issue ticket. But if you find some other things to fix to support PQC, let me know.