A system for encrypting and decrypting messages using a browser in either a web or wireless device or secure message client software for transmission to or from a web server on the Internet connected to an email server or message server for the situation where the sender does not possess the credentials and public key of the recipients. The encryption and decryption is conducted using a standard web browser on a personal computer or a mini browser on a wireless device, or message client software on either a personal computer or wireless devices such that messages transmitted to the web or wireless browser or message client software can be completed and encrypted and signed by the user such that encrypted and signed data does not require credentials and public key of the recipients. A method for delivering and using private keys to ensure that such keys are destroyed after use is also provided. A method of transmitting encrypted messages to a web or wireless browser or message client and decrypting and verifying such messages by recipients who do not possess or who are not enrolled in a PKI and do not have private keys. A method for authenticating the sender/user of the browser, and a method for accessing or generating public and private keys for encrypting and decrypting messages for recipients who are not enrolled in a public key infrastructure.