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 Steganography ( ) is the practice of representing information within another message or physical object, in such a manner that the presence of the information is not evident to human inspection. In computing/electronic contexts, a computer file, ...

. 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 Probability is the branch of mathematics concerning numerical descriptions of how likely an Event (probability theory), event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and ...

p(x,A)

and item

y

occurs with probability

p(y,A)

, then a random number is used to choose between outputting

x

y

with probability

p(x,A)

p(y,A)

respectively. Even more sophisticated models use reversible

Turing machine A Turing machine is a mathematical model of computation describing an abstract machine that manipulates symbols on a strip of tape according to a table of rules. Despite the model's simplicity, it is capable of implementing any computer algor ...

References

* * * Steganography {{Crypto-stub