Search of an information message in noisy code blocks at repeated data transmission

The security model using the method of code noising is considered. It is assumed that the information blocks of length $k$ contain a fixed message $m$ of length $l\leq k$ on a fixed position $q$, $1\leq q\leq k-l+1$, and an observer gets noisy codewords of length $n$ through a binary symmetric channel with error probability $({1-\Delta})/2$, $0<\Delta\leq1$. The aim of the observer is to find the unknown message $m$, when position $q$ is unknown, and the length $l$ is known. We propose a method for finding $m$ and obtain an estimate for a sufficient number of observed codewords needed to recover the message $m$ in this way.