关键词: 试题伪装, 无嵌入, 非直接传输, 无载体信息隐藏, 随机码本

Abstract:

In traditional no-embedding, search-based coverless information hiding methods, there exist some shortages such as small capacity, requiring or maintaining a large database about texts or images with a high search cost. To address these problems, a coverless test paper disguise method combined with non-direct transmission and random codebook is proposed. Firstly, to avoid direct transmission of secret information, secret information is coded by random codebook which has been scrambled by pseudo-random sequence. Secondly, the coded secret information is converted into 32-decimal digit sequence and further expressed by 24-decimal and 9-decimal digit sequences. Finally, each 24-decimal and 9-decimal digits in these two sequences are disguised by the key based random offsets relative to option arrangement order in choice question and answer of blank-flling question respectively in a random generated test paper. Comparing with the existed methods, the proposed method avoids the direct transmission of secret information and does not require extra carrier modifcation by introducing direct stego test paper generation. The proposed method does not require a large database, not require any search cost. It depends on the correct key to obtain transmitted secret information with a high hiding capacity.

Key words: non-direct transmission, random codebook, coverless information hiding, without embedding, test paper disguise