The sender first extracts features F from the ECG signals to form a session key Thand F is used as the root to build an ECG monic polynomial. Only the receiver with similar features set to F can reconstruct the polynomial and then regenerate K.
However, there is one special case which is amenable to solution for any value of n, namely the one in which all the coefficients equal zero except [a.sub.n] = 1 and [a.sub.0] = -1; then, the following reduced monic polynomial results:
where [B.sup.+] is a monic polynomial whose zeros are stable and so well damped that they can be canceled by the controller and [B.sup.-] corresponds to the unstable or poorly damped factors that cannot be canceled.
[alpha](s) is a monic polynomial of unknown coefficients, while [beta](s) is a monic polynomial of known coefficients that are determined by poles [[lambda].sub.1], [[lambda].sub.2], ..., [[lambda].sub.n-m]}.
Since [c.sub.m](z) is arbitrary monic polynomial of degree [v.sub.m], the linear space V over R spanned by the rows of polynomial vector [a(z)-d(z)], consists of all polynomials [lambda](z) over R[z] with