1. A portable token device fabricated on a portable medium and sized so as to be readily carried or worn by a user comprising: a token device medium substantially credit card-sized so as to be readily carried or worn by a user and having fabricated therein: a secure storage device for storing a user's private key, wherein said at least one private key is used to perform digital signatures associated with said user and wherein said user's private key has an associated public key identified with said user; a clock for providing an indication of date and time; a communication port for receiving a value to be digitally signed and for emitting an output; a processor device coupled to said communication port and said clock for receiving said value to be digitally signed and said indication of date and time and for performing at least one digital signature with said at least one private key for output to said communication port.