Alphabetum Kaldeorum

It can be found in a complete version, together with other non-Latin alphabets, in a manuscript from the year 1428, now in the library at the University of Munich (Cod.

The Alphabetum Kaldeorum was meant primarily for the encipherment of diplomatic correspondence; its alphabet implies that predominantly Latin texts were coded: u and v are equated; w was to be written as double v; j is missing.

For frequently arising letters the Alphabetum Kaldeorum provides several different versions, which were used at random so that a decipherment attempt using the classical frequency analysis method should fail.

"Nulla", cipher-letters with no plaintext assignment which were to be ignored, were also often added to the enciphered texts to further render frequency-analysis useless.

Even Rudolf's gravestone in the Stephansdom in Vienna carries an inscription enciphered using the Alphabetum Kaldeorum, which gives the names and titles of the duke.