; Find a prime from length and textually supplied entropy.
(let ((RC4 (fileVal "RC4"))(pias (fileVal "pias"))(Do ((fileVal "Do") 'Do)))
(lambda (n seed) (let* ((state (RC4 seed)) (lim (expt 2 (- n 1)))
  (B (+ 1 (((state 'rbi) (expt 2 20))))))
  (let ((nb (state 'sb))) (Do 768 (lambda (i) (nb))))
  (let rec ((A (+ lim (((state 'rbi) lim)))))
    (let ((cp (pias A B))) (if (number? cp) (number->string cp 16)
      (rec (+ 1 A))))))))

((fileVal "fndPrm") 1024 "fit")
=> "d6e2cc0799d26fd889bfd4b4f81cacb6d933f8c2bfb1d4e2e2d6f0a1e8a6f167cda7f05ead8dc1900c9304081429208cb016665608a991ae5abf8fd7c61ae1aae88ef7e74ebf3de45bddac5db8c2163d9c4eeaccb52ffe921081b41b8bb8a3bdebef04dbde05aa0e251d4522ffb2ce2259041c6bf6beeaba9c6372d5cd1d6745"