Support PQC algorithm(MLDSA) for signing/verifying Model

[bbug96-crkim]

What needs to be improved?

• Currently, only eckey, sigstore, and pkcs11 are supported.
• I'd like to add functionality to use the PQC algorithm (ML-DSA) for model signing/verifying.

What should be done?

• I plan to add functionality to select the PQC-related algorithm (ML-DSA) when signing models using a key in the CLI, enabling PQC-based signing/verification.

Has there been any related work before?

• This is the first time this has been released in open source, but most cryptography features support PQC, and it's time to support it.

Any relevant links or material?

• https://csrc.nist.gov/Projects/post-quantum-cryptography

[sevansdell]

I support this and would work to find an engineer from my company who can support if needed.

[bbug96-crkim]

@sigstore/model-transparency-codeowners, @sigstore/model-transparency

I submitted a pull request after making code changes related to this issue. I believe this issue requires review, so I'd like to inquire if we can review or discuss this further.

[Hayden-IO]

I've left some thoughts on this topic on #596 (comment), we can move the discussion into this issue.

With PQC adoption, the first question is why now?. Rushing adoption of a new algorithm risks adding long-term technical debt and possibly even security risks for algorithms and implementations that have not yet been proven secure. We need a solution before 2035 based on NIST's timeline, with 2030 being where we start deprecating existing algorithms. Right now, I'd encourage experimentation rather than changes to the upstream clients.