DSA no longer approved for signature generation by FIPS 186-5

[msedzins]

FIPS 186-4 referenced in README.md has been superseded by FIPS 186-5 which no longer approves DSA for digital signature generation. DSA may be used only to verify already existing signatures.

Link:
https://csrc.nist.gov/pubs/fips/186-5/final

Should we add this information as part of README.md?

[tarcieri]

Moving to verification only, possibly placing signing under a hazmat feature, seems like a reasonable approach to me

[msedzins]

I tried to put signing under hazmat feature (in signing_key.rs) but tests stopped working (for example: signature.rs/signer_verifier_signature).

I don't think it's a good idea to put all those tests under hazmat feature.
It would be good if we could enable hazmat feature for dev/test profiles by default but it is not supported.

Any other possible approach?

[tarcieri]

It's fine to gate the tests on the corresponding feature. They won't work unless the feature is enabled.

[msedzins]

Please have a look at PR #859

There are two main issues there:

1. Tests fail because of examples (they work only with signing enabled). But those examples (generate.rs/sign.rs) don't make sense without signing enabled.
2. I think we are missing a test that that verify already existing signatures (current tests first generate signature and then verify them, which doesn't work without signing enabled).

[tarcieri]

You can also feature gate the examples. Here's an example of a pattern we use to do this:

https://github.com/RustCrypto/SSH/blob/f741cf0/ssh-key/src/lib.rs#L44-L45

[msedzins]

I think we are talking about different "examples".

In my case example is just a binary crate, binary crate must have "main" function. So, the error I get is this:

% cargo run --package dsa --example sign

error[E0601]: `main` function not found in crate `sign`
  --> dsa/examples/sign.rs:35:2
   |
35 | }
   |  ^ consider adding a `main` function to `dsa/examples/sign.rs`

Of course, I can add dummy "main", but I'm not sure if it makes sense.

[tarcieri]

You can use required-features in Cargo.toml for that

[msedzins]

done. please have a look at PR #859