Patent ID: 8868039

Claim:
A method employing a first device, comprising the acts: using one or more sensors in said first device obtaining one or more context parameters selected from the list: information based on visual stimulus recently sensed by the first device; sensed radio transmissions; sensed RFID data; orientation sensor data; magnetometer data; audio classification data, received from a logical sensor fed by information both from an audio sensor and another sensor in said first device; activity classification data; and barometric sensor data; generating an image based, at least in part, on said obtained parameter(s); and presenting the image, for sensing by a camera of a second device, to authenticate a transaction, in which the generating act comprises encrypting a first of said obtained context parameters with a private key associated (a) with the first device, or (b) with a user of the first device, and representing the encrypted first context parameter as a barcode or digital watermark in the image.