Unsent messages are securely stored in a client by determining whether a connection to a server exists. If the connection exists, the message can be sent using the intended recipient's public key. In response to a determination that a connection from the client to a server does not exist, information from the client can be used to encrypt a modulated data signal that is to be sent from the client to the server. The encrypted modulated data signal is stored on the client. When a determination is made that a connection from the client to the server exists, information from the client is used to decrypt the encrypted modulated data signal.