Abstract: A system and method authenticates a user if the user is associated with a certificate on a device the user is using to communicate, even if other users are also associated with the same certificate and/or the user is associated with other certificates on other devices.

Abstract: A system and method authenticates an e-mail message containing a code that may be sent as part of an advertising campaign. The code is a hashed hash result of a combination of the e-mail address to which the message was sent and a pass phrase for the campaign, along with an identifier of the campaign. To authenticate the message, the user supplies the user's e-mail address and the code and the system and method parses the code to identify the campaign identifier and hashed hash result, looks up the pass phrase using the campaign identifier, hashes the campaign identifier and e-mail address and hashes that hash result. If the hashed hash results match, the system and method indicates the message is authentic and otherwise, indicates the message is not authentic.

Abstract: A system and method authenticates users via any two or three of 1) Something the user knows; 2) Something the user has; and 3) A physical characteristic of the user.

Abstract: A system and method allows some or all of an e-mail message, such as the sender or its contents, to be authenticated, for example, to identify a message as potential spam.

Abstract: A system and method communicates information from an entity that a registry can use to authenticate the entity to a user. If the registry authenticates the entity, it displays information that represents a shared secret between the registry and the user.

Abstract: A system and method allows a user to authenticate a communication from a computer system, a computer system to authenticate a user, or both. When a user requests a web page from the web site, customization information that is recognizable to the user is provided to allow the user to authenticate the web site. A signed, encrypted persistent file stored on the user's computer system or installed on a different computer system, or a trusted computing subsystem allows the web site to authenticate the user. If the user is using a system that will not allow that user to be authenticated, the user may instruct the system to continue providing information without the user's customization information. The system and method may be used to allow the user to authenticate an e-mail message or its source, and Flash movies or other computer code may be used if the user's e-mail client does not employ cookies.

Abstract: A system and method allows a user to authenticate a web site, a web site to authenticate a user, or both. When a user requests a web page from the web site, customization information that is recognizable to the user is provided to allow the user to authenticate the web site. A signed, encrypted cookie stored on the user's system allows the web site to authenticate the user.