module Net::SSH::Transport::HMAC

def self.get(name, key="", parameters = {})

given, the new instance will be initialized with that key.
Retrieves a new hmac instance of the given SSH type (+name+). If +key+ is 
def self.get(name, key="", parameters = {})
  impl = MAP[name] or raise ArgumentError, "hmac not found: #{name.inspect}"
  impl.new(Net::SSH::Transport::KeyExpander.expand_key(impl.key_length, key, parameters))
end

def self.key_length(name)

Retrieves the key length for the hmac of the given SSH type (+name+). 
def self.key_length(name)
  impl = MAP[name] or raise ArgumentError, "hmac not found: #{name.inspect}"
  impl.key_length
end