A method of authenticating a user of a mobile communication device , comprising: directing, by a first application or program executing on the mobile communication device , transmission, from the mobile communication device to a security server , of a request for authentication of the user in connection with either (i) the user logging into or (ii) the user entering into a transaction with a network site ; receiving, by a second application or program executing on the mobile communication device , the request for authentication from the security server ; directing, by the second application or program , presentation by the mobile communication device of the received request for authentication to the user; receiving, by the second application or program , a user input to the mobile communication device indicating that the requested authentication should proceed; directing, by the second application or program in response to the received user input, transmission, from the mobile communication device to the security server , of an indication that the requested authorization should proceed; receiving, by the second application or program from the security server , a personal identification number (PIN), in response to the transmission of the indication that the requested authorization should proceed; storing, by the second application or program , the received PIN in a public data store within the mobile communications device ; retrieving, by the first application or program , the stored PIN from the public data store; and directing, by the first application or program , transmission, from the mobile communications device to the network site, of the retrieved PIN, to authenticate the user or transaction to the network site ; wherein preferably the mobile communication device is a smart phone. directing, by a first application or program executing on the mobile communication device , transmission, from the mobile communication device to a security server , of a request for authentication of the user in connection with either (i) the user logging into or (ii) the user entering into a transaction with a network site ; receiving, by a second application or program executing on the mobile communication device , the request for authentication from the security server ; directing, by the second application or program , presentation by the mobile communication device of the received request for authentication to the user; receiving, by the second application or program , a user input to the mobile communication device indicating that the requested authentication should proceed; directing, by the second application or program in response to the received user input, transmission, from the mobile communication device to the security server , of an indication that the requested authorization should proceed; receiving, by the second application or program from the security server , a personal identification number (PIN), in response to the transmission of the indication that the requested authorization should proceed; storing, by the second application or program , the received PIN in a public data store within the mobile communications device ; retrieving, by the first application or program , the stored PIN from the public data store; and directing, by the first application or program , transmission, from the mobile communications device to the network site, of the retrieved PIN, to authenticate the user or transaction to the network site ; wherein preferably the mobile communication device is a smart phone. <EOS>