Zenker and Lichtenfels ciphers

The Zenker cipher, initially employed by the imperial offices for the purposes of document encryption, was first developed in the seventh century by a civil servant named Erich Zenker. He invented a square table where the first row corresponded to ordered letters of the alphabet, and the rest were the previous row cyclically shifted by a constant amount of symbols to the right. To encrypt a message, one would choose a word or a combination of words written without spacing and superimpose the key string, repeated if need be, onto the text that requires encryption. The encryptor would then choose the letter from the column corresponding to the letter of an unencrypted text and the row corresponding to the letter of the key in a certain position. His initial cipher proved all but unbreakable to conventional means and was thus accepted into the imperial employment for encryption of critical messages, including the emperor's own correspondence. At a later time Zenker also introduced an improvement to his cipher: he proposed that at regular intervals of a few years the tables are to be remade with a new row shift value, and a multiple of the ratio, written in words and encrypted, is to be sent out to the intended users along with some simple message. This strengthened the cipher additionally, requiring the potential analyst to contend with a perpetually mutating method of encryption.
The cipher was, however, not without weaknesses, long messages being especailly susceptible to decryption by the virtue of key repetition. Key repetition lead to repetition of sequences in encrypted text, which allowed to narrow the guess for the key length and thus simplify breaking up the cipher into a series of much simpler shift ciphers, which easily yielded even to trying out all possible keys.
In XII century the renowned mathematician professor Otto-Heinrich von Lichtenfels pointed out this weakness and convinced the then-Master of Offices Johann von Ladendorf to commission an improvement to the cipher. Von Lichtenfels, instead of improving the existing method, designed a new unique and elaborate cipher, relying on numbers rather than letters. Moreover, he encrypted not by letter, like his predecessors did, but rather by syllable, substituting words with homphones if need be, thus increasing the complexity of decryption. To further protect his cipher from being broken, von Lichtenfels inserted into his cipher table a number of specific sequences that served to confuse the decrypter, for example corresponding to no text or urging the reader to strike out one or more preceding sequences, trailing sequences, or all trailing sequences until a stop sequence is reached. Additionally, a number of sequences were meant to be appended to encoded words to modify them with respect to the rules of conjugation and declension. Tables were broken up into a number of distinct sub-tables to prevent concentration of information. Lichtenfels cipher, having been found of superb quality, was then accepted as a new standard for the imperial encryption. Despite the existence of decryption tables, it has not been broken by foreign powers so far due to exceptional caution exercised in sending out the tables.