# File lib/net/ssh/authentication/key_manager.rb, line 132
132:         def sign(identity, data)
133:           info = known_identities[identity] or raise KeyManagerError, "the given identity is unknown to the key manager"
134: 
135:           if info[:key].nil? && info[:from] == :file
136:             begin
137:               info[:key] = KeyFactory.load_private_key(info[:file], options[:passphrase])
138:             rescue Exception, OpenSSL::OpenSSLError => e 
139:               raise KeyManagerError, "the given identity is known, but the private key could not be loaded: #{e.class} (#{e.message})"
140:             end
141:           end
142: 
143:           if info[:key]
144:             return Net::SSH::Buffer.from(:string, identity.ssh_type,
145:               :string, info[:key].ssh_do_sign(data.to_s)).to_s
146:           end
147: 
148:           if info[:from] == :agent
149:             raise KeyManagerError, "the agent is no longer available" unless agent
150:             return agent.sign(identity, data.to_s)
151:           end
152: 
153:           raise KeyManagerError, "[BUG] can't determine identity origin (#{info.inspect})"
154:         end