12-01-2013, 12:43 AM
image steganography ppthich in turn means that the reliability of steganalysis detector will also
increase. Accordingly, a stego technique is said to be perfectly secure if
D(Pc||Ps)=0(Pc and Ps are equal), and -secure if the relative entropy
between Pc and Ps is at most , D(Pc||Ps) = . Perfectly secure algorithms
are shown to exist, although they are impractical [5]. However, it should
be noted that this definition of security is based on the assumption that
the cover-object and stego-object are independent, identically distributed
(i.i.d.) vectors of random variables.
Since Wendy uses hypothesis testing in distinguishing between stego-
objects and cover-objects, she will make two types of errors, namely, type-
I and type-II errors. A type-I error, with probability a occurs, when a
cover-object is mistaken for a stego-object (false alarm rate), and a type-
II error, with probability ß, occurs when a stego-object is mistaken for a
cover-object (miss rate). Thus bounds on these error probabilities can be
computed using relative entropy, thereby relating steganogr
increase. Accordingly, a stego technique is said to be perfectly secure if
D(Pc||Ps)=0(Pc and Ps are equal), and -secure if the relative entropy
between Pc and Ps is at most , D(Pc||Ps) = . Perfectly secure algorithms
are shown to exist, although they are impractical [5]. However, it should
be noted that this definition of security is based on the assumption that
the cover-object and stego-object are independent, identically distributed
(i.i.d.) vectors of random variables.
Since Wendy uses hypothesis testing in distinguishing between stego-
objects and cover-objects, she will make two types of errors, namely, type-
I and type-II errors. A type-I error, with probability a occurs, when a
cover-object is mistaken for a stego-object (false alarm rate), and a type-
II error, with probability ß, occurs when a stego-object is mistaken for a
cover-object (miss rate). Thus bounds on these error probabilities can be
computed using relative entropy, thereby relating steganogr