Abstract: A system for detecting whether a device seeking communication with a server is a returning device that previously communicated with the server includes a database that stores groups of device attributes based on observable device characteristics and unique identifiers. The database is generally not accessible to the devices. Each attribute group and the associated device identifier (DID) can uniquely identify a particular device, and the associated DID is generally not derivable from the attributes. The database may satisfy a uniqueness property so that each attribute value in the database may also uniquely identify a device.

Abstract: A system for detecting whether a device seeking communication with a server is a returning device that previously communicated with the server includes a database that stores groups of device attributes based on observable device characteristics and unique identifiers. The database is generally not accessible to the devices. Each attribute group and the associated device identifier (DID) can uniquely identify a particular device, and the associated DID is generally not derivable from the attributes. The database may satisfy a uniqueness property so that each attribute value in the database may also uniquely identify a device.

Abstract: A system for detecting whether a device seeking communication with a server is a returning device that previously communicated with the server includes a database that stores groups of device attributes based on observable device characteristics and unique identifiers. The database is generally not accessible to the devices. Each attribute group and the associated device identifier (DID) can uniquely identify a particular device, and the associated DID is generally not derivable from the attributes. The database may satisfy a uniqueness property so that each attribute value in the database may also uniquely identify a device.

Abstract: A system facilitates secure communication between an authorized user device and two or more servers via two or more channels that are associated with the respective servers. For each communication channel, the system receives a device identifier for the authorized user device and links the device identifiers together via another identifier, thereby allowing the system to recognize that the different device identifiers identify the same authorized user device. The system can identify an unauthorized device masquerading as the authorized user device by determining that a communication from the unauthorized device does not include another identifier linking the two or more device identifiers and/or by determining that a device identifier computed during the registration process is different from a linked identifier.

Abstract: A system for detecting whether a device seeking communication with a server is a returning device that previously communicated with the server includes a database that stores groups of device attributes based on observable device characteristics and unique identifiers. The database is generally not accessible to the devices. Each attribute group and the associated device identifier (DID) can uniquely identify a particular device, and the associated DID is generally not derivable from the attributes. The database may satisfy a uniqueness property so that each attribute value in the database may also uniquely identify a device.

Abstract: A system for detecting whether a device seeking communication with a server is a returning device that previously communicated with the server includes a database that stores groups of device attributes based on observable device characteristics and unique identifiers. The database is generally not accessible to the devices. Each attribute group and the associated device identifier (DID) can uniquely identify a particular device, and the associated DID is generally not derivable from the attributes. The database may satisfy a uniqueness property so that each attribute value in the database may also uniquely identify a device.

Abstract: A system for detecting whether a device seeking communication with a server is a returning device that previously communicated with the server includes a database that stores groups of device attributes based on observable device characteristics and unique identifiers. The database is generally not accessible to the devices. Each attribute group and the associated device identifier (DID) can uniquely identify a particular device, and the associated DID is generally not derivable from the attributes. The database may satisfy a uniqueness property so that each attribute value in the database may also uniquely identify a device.

Abstract: A system facilitates secure communication between an authorized user device and two or more servers via two or more channels that are associated with the respective servers. For each communication channel, the system receives a device identifier for the authorized user device and links the device identifiers together via another identifier, thereby allowing the system to recognize that the different device identifiers identify the same authorized user device. The system can identify an unauthorized device masquerading as the authorized user device by determining that a communication from the unauthorized device does not include another identifier linking the two or more device identifiers and/or by determining that a device identifier computed during the registration process is different from a linked identifier.