anchor.diff:  (defun random-sequence () (random-bytes (random 32)))
   
   (dotimes (i 5)
  -  (setf l (for i in (counter 0 12) collect (ratchet-encrypt rsa (random-sequence))))
  -  (expect-error (ratchet-decrypt rsb (1st (last l)) nil))
  -  (for msg in l do (ratchet-decrypt rsb msg nil))
  -  (setf l (for i in (counter 0 9) collect (ratchet-encrypt rsa (random-sequence))))
  -  (for msg in (reverse l) do (ratchet-decrypt rsb msg nil))
  -  )
  +  (bb l (for i in (counter 0 12) collect (ratchet-encrypt rsa (random-sequence)))
  +      (expect-error (ratchet-decrypt rsb (1st (last l)) nil))
  +      (for msg in l do (ratchet-decrypt rsb msg nil))
  +      (setf l (for i in (counter 0 9) collect (ratchet-encrypt rsa (random-sequence))))
  +      (for msg in (reverse l) do (ratchet-decrypt rsb msg nil))
  +      ))
  
positive.code: 
  (defun kdf-ck (ck) (kdf-rk "" ck))
  
  (defun generate-dh () (sc4-key (random-bytes 32)))
  
  (define-class ratchet-header pk pn n)
  
  (define-print-method (ratchet-header pk pn n) "#<Ratchet-header ~A ~A ~A>" pk pn n)
  
negative.code:       (unless otpk (error "OTPK ~A unknown" otpkid))
        (del otpk-dict otpkid)
        (push otpkid used-otpkids)
        dh4 (dh otpk ek)
        (hkdf (cat dh1 dh2 dh3 dh4))))
  
  (define-method (x3dh-rx (user sc4-user) (hdr vector))
  