Abstract: A secure instant messaging system integrates secure text instant messaging and secure file transfers into existing instant messaging systems. At least one certificate authority (CA) is provided that issues a security certificate to a user that binds the user's instant messaging screen name to a public key which is used by other users to encrypt messages and files sent to the user and by the user to decrypt the received messages and files. A subscriber database is used by the CA to keep track of valid users and their associated information, such as: user screen names, user subscription expiration dates, and enrollment agent information. A user sends his certificate to the invention's instant messaging server which publishes the user's certificate to other users by creating a hash value of the user's certificate and sending it to the other users which allows the recipients to decide if they need to update their caches with a new copy of the user's certificate.

Abstract: The invention generates a temporary digital certificate with a useful life of only a few minutes to a few hours. An expiration time is attached to such temporary digital certificate by a secure computer platform that is presented with a user's smart-card. Expiration dates one or two years after the issuance of the smart-card are conventional. A digital certificate issued by a central authority is carried within the smart card and is used by the secure computer platform to generate temporary digital certificate. The temporary digital certificate functions as a proxy digital certificate that will allow the user to immediately pocket the smart card and thus avoid the possibility of forgetting it in a card reader.