module Epithet::Scrypt

Provider registry & classes for the scrypt implementations.

A scrypt provider is any class that can be instantiated with the scrypt parameters salt, N, r, p, and length, has a predicate singleton method auto? indicating willingness to operate, and an instance method ikm(passphrase) that derives the key material. Automatic selection picks the most recently registered willing provider.

Of the builtin providers, we prefer OpenSSL::KDF.scrypt when the platform supplies it, then JRuby’s BouncyCastle implementation, and finally an already-loaded scrypt gem. If none of these are available, selection falls through to a base class which raises NotImplementedError at the point of use.

Epithet deliberately does not require the optional scrypt gem itself; an application relying on the SCryptGem provider should bundle and require scrypt before configuring Epithet.

You may register a custom scrypt provider with the necessary signature, even after Epithet has loaded:

class MyProvider < Epithet::Scrypt::Base
  def ikm(passphrase)
    #...
  end
end
Epithet::Scrypt.register(MyProvider)

and this will be unconditionally preferred unless you also define a selective auto? method.

Your ikm method should return length bytes of key material.

Using this mechanism as a hook to deviate from the scrypt algorithm is not recommended; the better move would be to substitute a variant key generator in the Epithet::Config parameters, or supply IKM to an Epithet::Keygen.