Encrypted JPEG image retrieval using block-wise feature comparison

Bitstream-Based JPEG Image Encryption with File-Size Preserving

“…Next, we compare our method with the previous works [1], [17], in terms of the file sizes. Table II shows the file sizes of encrypted JPEG images under various conditions.…”

“…However, other encryption methods could not preserve the same file sizes, because they do not consider the effect of byte stuffing. [17] 24,281(+2) 43,865(-14) 106,553(+5) EtC [1] 24,767(+488) 44,487(+608) 108,262(+1,714)…”

“…Several bitstream based encryption methods have also been proposed [12]- [17]. For JPEG 2000 images, some bitstreambased encryption methods have been proposed in consideration of the generation of special marker codes and without changing the file size [12]- [14].…”

“…For JPEG 2000 images, some bitstreambased encryption methods have been proposed in consideration of the generation of special marker codes and without changing the file size [12]- [14]. Even for JPEG images, some bitstream-based encryption methods have been proposed, but the file size of the encrypted bitstream has changed by the occurrences or disappearances of the JPEG marker code [15]- [17]. For example, in [15], encryption is performed while keeping the file size by rearranging the run lengths of AC coefficients.…”

“…In this case, the encrypted bitstream can not be correctly decoded or the file size of the encrypted bitstream is changed. On the other hand, in the methods of [16], [17], bitstream-based block scrambling and coefficient scrambling are implemented. In these methods, in order to accurately hold the JPEG format, encryption processing is executed the byte stuffing operation which prevent accidental generation of markers by the arithmetic encoding procedures.…”