An anonymous reader writes "Scientists are claiming to have a new type of optical security that doesn't require embedment. Optical security includes many different options but up until now they have all required that the secret image be embedded in a host image which left it vulnerable. From the article: 'To address this problem of finding the secret image in the watermark, scientists have developed a new optical security method that doesn't require embedment. Instead, the technique uses a phase retrieval algorithm to generate specific optical and phase keys that extract the secret information when applied. The optical keys contain information and are distributed to an individual through a personal identification number (PIN). The information contained in the phase keys (the main source for determining extraction) is distributed to the individual separately.'"