關於 Jsteg 的點點滴滴 (五) : N. Provos

Niels Provos & Peter Honeyman 在 2001 年的技術報告 "Detecting Steganographic Content on the Internet" 中是這樣描述 Jsteg 的:

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JSteg is an addition by Derek Upham to the Independent JPEG Group's JPEG Software library. The DCT coefficients are modified continuously from the beginning of the image. JSteg does not support encryption and has no random bit selection.

The message data is prepended with a variable size header. The first five bits of the header express the size of the length field in bits. The following bits contain the length field that expresses the size of the embedded content.

IEEE Security & Privacy 在 2003 May/June 這一期中有一篇文章 "Hide and Seek: An Introduction to Steganography", 在 P. 34 的 Figure 3 中, 提到 Jsteg 的演算法。Niels Provos & Peter HoneyMand 是這樣描述 Derek Upham 的 Jsteg 嵌入法:

Derek Upham's JSteg was the first publicly available steganographic system for JPEG images. Its embedding algorithm sequentially replaces the least-significant bit of DCT coefficients with the message's data (see Figure 3). The algorithm does not require a shared secret; as a result, anyone who knows the steganographic system can retrieve the message hidden by JSteg.