Patent ID: 7095855

Claim:
A method for securely encoding and transmitting a message by an originating device to one of a plurality of recipient devices, said message being associated with a particular one of a plurality of applications running on the originating device, the method comprising the steps of: (a) determining a device identifier for the originating device, and an application identifier for each of the plurality of applications thereby forming a plurality of device-identifier/application identifier pairs; (b) associating a secret value with each device identifier/application-identifier pair; (c) wherein each said secret value is known to the originating device and to one of the recipient devices; (d) generating a message value by a first process, using the device identifier, a particular application identifier and an application value, said application value indexing said message; (e) combining the message value with said secret value associated with the particular application identifier to establish a corresponding secret message value; (f) applying the secret message value and the message to an encoding process to form a secure message block; and (g) combining the device identifier, the application identifier, the application value and the secure message block, to form a secure message for transmission, said secure message being decodable, dependent upon the device identifier, the particular application identifier and the application value which are outside the received secure message block, by said recipient device to which said secret value associated with the particular application identifier is known, said recipient device thereby recovering the message, the device identifier, the particular application identifier and the application value.