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Mimic function

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Source updated December 28, 2022

A mimic function changes a file $A$ so it assumes the statistical properties of another file $B$ . That is, if $p(t,A)$ is the probability of some substring $t$ occurring in $A$ , then a mimic function $f$ , recodes $A$ so that $p(t,f(A))$ approximates $p(t,B)$ for all strings $t$ of length less than some $n$ . It is commonly considered to be one of the basic techniques for hiding information, often called steganography.

The simplest mimic functions use simple statistical models to pick the symbols in the output. If the statistical model says that item $x$ occurs with probability $p(x,A)$ and item $y$ occurs with probability $p(y,A)$ , then a random number is used to choose between outputting $x$ or $y$ with probability $p(x,A)$ or $p(y,A)$ respectively.

Even more sophisticated models use reversible Turing machines.

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This article is adapted from the Wikipedia article “Mimic function”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.

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