feat: CRP-2802 add sign_with_bls to utils

[altkdf]

Said function calls the management canister's vetkd_derive_vetkey API with a fixed transport public key (G1 identity) and removes c1 more efficiently than in EncryptedVetKey::decrypt_and_verify.

[altkdf]

Once we have abstractions for VRF, BLS signatures, etc., we could make derive_public_vetkey an internal function if we are concerned that someone might misunderstand what this function is for. Currently, we need it public for testing with Pocket IC.

[altkdf]

@fspreiss @randombit any better ideas for the function (derive_public_vetkey) name? I only thought of 2 so far: derive_unencrypted_vetkey and derive_public_key. Both have downsides IMO: "unencrypted" may not mean much to everyone, especially if people don't fully understand how the protocol works, and "public" can be confused with the vetkd public verification key.

[randombit]

any better ideas for the function (derive_public_vetkey) name? I only thought of 2 so far: derive_unencrypted_vetkey and derive_public_key. Both have downsides IMO: "unencrypted" may not mean much to everyone, especially if people don't fully understand how the protocol works, and "public" can be confused with the vetkd public verification key.

derive_public_key seems definitely confusing

Maybe create_bls_signature or sign_with_bls

[altkdf]

any better ideas for the function (derive_public_vetkey) name? I only thought of 2 so far: derive_unencrypted_vetkey and derive_public_key. Both have downsides IMO: "unencrypted" may not mean much to everyone, especially if people don't fully understand how the protocol works, and "public" can be confused with the vetkd public verification key.

derive_public_key seems definitely confusing

Maybe create_bls_signature or sign_with_bls

in the timelock encryption case, that would still be a vetkey 🤷‍♂️

[altkdf]

TODO: check the validity of the obtained BLS signature once #108 is merged.

[randombit]

LGTM besides adding the signature verification

[fspreiss]

Very nice, thanks @altkdf! Here are a few minor comments.

[fspreiss]

Thanks, @altkdf!