A High Capacity Test Disguise Method Combined With Interpolation Backup and Double Authentications

To improve the hidden capacity of a single question, further avoid the absence of authentication and provide self-repair ability, this paper proposes a high capacity test disguise method combined with interpolation backup and double authentications. Firstly, secret byte sequence is backed up and further encoded to a backup index sequence by secret information backup and encoding strategy. Secondly, a test question database divided into eight sets is created. Finally, the backup index sequence is disguised as a stego test paper using 24 different candidate answer orders and 4-bit hash values. In restoration, double authentications are applied to authenticate candidate restored value, and the most reliable candidate restored values are obtained by the reliable calculation to reconstruct secret information. The experimental results and analysis show that the proposed method can distinguish error candidate restored values, and calculate the reliability of each restored byte. Moreover, it has excellent self-repair ability with a higher hidden capacity of a single question.