Trithemius cipher
... that the Trithemius cipher, created by Johannes Trithemius, is vulnerable to attack because it lacks a key, which is said to break a rule of cryptology called Kerckhoffs' principle?
... that the <b id="mwD1g"><a class="mw-redirect" href="./Trithemius_cipher" id="mwD1k" rel="mw:WikiLink" title="Trithemius cipher">Trithemius cipher</a></b>, created by <a href="./Johannes_Trithemius" id="mwD1o" rel="mw:WikiLink" title="Johannes Trithemius">Johannes Trithemius</a>, is vulnerable to attack because it lacks a <a href="./Key_(cryptography)" id="mwD1s" rel="mw:WikiLink" title="Key (cryptography)">key</a>, which is said to break a rule of <a class="mw-redirect" href="./Cryptology" id="mwD1w" rel="mw:WikiLink" title="Cryptology">cryptology</a> called <a class="mw-redirect" href="./Kerckhoffs'_principle" id="mwD10" rel="mw:WikiLink" title="Kerckhoffs' principle">Kerckhoffs' principle</a>?