The subject invention provides a unique system and method that facilitates creating HIP challenges (HIPs) that can be readily segmented and solved by human users but that are too difficult for non-human users. More specifically, the system and method utilize a variety of unique alteration techniques that are segmentation-based. For example, the system and method employ thicker arcs or occlusions that do not intersect characters already placed in the HIP. The thickness of the arc can be measured or determined by the thickness of the characters in the HIP. In addition to increasing the thickness, the arcs can be lengthened because longer arcs tend to resemble pieces of characters and may be harder to erode. Usability maps can be generated and used to selectively place clutter or occlusions and to selectively warp characters or the character sequence to facilitate human recognition of the characters.