Code review comment for lp:~mir-team/mir/attestable-timestamps-server

Just a bit of musing, not anything that requires action:

The create functions could be:

std::unique_ptr<CookieFactory> create_from_secret(std::vector<uint8_t> const& save_secret);
std::unique_ptr<CookieFactory> create_saving_secret(std::vector<uint8_t>& save_secret, unsigned secret_size = 2*minimum_secret_size);

That might be more convenient for code that doesn't care about the secret size. There could also be other variants:

std::unique_ptr<CookieFactory> create_keeping_secret(unsigned secret_size = 2*minimum_secret_size);

Which would support user code that just does:

    auto const cf = CookieFactory::create_keeping_secret();

Maybe not an important use case?

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It could also be convenient to include a definition of Secret:

    using Secret = std::vector<uint8_t>;

and use that in both the interface and user code.