Patent ID: 8893034

Claim:
A method for generating a multi-frame image rendering of a challenge-response test on a display, comprising: identifying a pattern defined by graphical elements, wherein each of the graphical elements is associated with a random lifetime; identifying a display region on the display for rendering an entry object from the multi-frame image of the challenge-response test; defining a foreground sampling window with an associated move vector, the foreground sampling window capturing the graphical elements of the pattern along a first path across the pattern, and the foreground sampling window having a non-patterned area defined by the entry object to be rendered; defining a background sampling window with an associated move vector, the background sampling window capturing the graphical elements of the pattern along a second path across the pattern, wherein the move vector of the background sampling window is different from the move vector of the foreground sampling window; and presenting the background sampling window and the foreground sampling window at the display region of the display, the foreground sampling window being overlaid on the background sampling window at the display region, such that the entry object of the challenge-response test is discernable from the pattern during a period of time when multiple frames are rendered due to the differing move vectors and is not discernable when the sample frames of the foreground and background sampling windows are static, wherein after generating each frame, the lifetime of the graphical element is decremented, and wherein when the lifetime of the graphical element reaches zero, assigning a new random position and new random lifetime to the graphical element.