def eval(w,t,x,msk,s):
<EOL>assertType(w, (str, int, long))<EOL>assertType(t, (str, int, long))<EOL>assertType(x, (str, int, long))<EOL>kw = genKw(w,msk,s)<EOL>beta = hashG1(t, x)<EOL>y = beta*kw<EOL>return y,kw,beta<EOL>
Pythia server-side computation of intermediate PRF output.
@w: ensemble key selector (any string, e.g. webserver ID)
@t: tweak (any string, e.g. user ID)
@x: message (any string)
@msk: Pythia server's master secret key
@s: state value from Pythia server's key table
@returns: (y, kw, dummy=None)
 where: y: intermediate result
        kw: secret key bound to w (needed for proof)
        beta: H(kw,t,x) (needed for proof)