last month
next month

Centre for the Study of Manuscript Cultures (CSMC)

03/2015 manuscript  of the month

The Manuscript That Nobody Can Read

The Hungarian Academy of Sciences in Budapest has a manuscript in its archives that still puzzles researchers to this day: the Rohonc Codex (K 114). This is written in a script that no-one understands. Are cryptological methods able to reveal what this book is about and what its purpose once was?

Fig. 1: fol. 40v und 41r. The Rohonc Codex is written in an unknown script;
nobody has been able to decipher it yet. > Enlarge

Although it may seem rather unusual at first, computer scientists who are normally concerned with bits and bytes also have good reason to take an interest in old manuscripts. This is because the discipline of cryptology is part of information science – and an extremely important matter in view of omnipresent network surveillance by the NSA and others. The idea of encrypting texts came to people’s minds well before the onset of computer technology, of course. Even medieval popes had messages encoded – like scholars and important military and commercial figures, they were not always willing to disclose the contents of their missives. This is why we can find a variety of encrypted documents (‘cryptograms’) from the past in archives today. Since there are only a small number of historians who focus on cryptology, however, merely a fraction of these works have been examined to date. Books that have been encrypted from beginning to end are certainly the ‘gems’ among all these cryptograms. A list the best-known cryptographic books currently includes 56 items and is likely to grow as time goes on.

Fig. 2: fols. 50v und 51r. The pictures in the Rohonc Codex show numerous
Christian motifs, for example the crucifixion, but none of these have helped
researchers decipher the document. > Enlarge

The most famous encrypted book of all is the Voynich Manuscript – a work from the late Middle Ages. Unlike most other works of this kind, the Voynich Manuscript is still waiting to be decrypted. The Rohonc Codex, a far less familiar manuscript from former Western Hungary, is another such case. This handmade work is 12×10 cm in size and kept in Budapest.

One reason why it is difficult to even speculate about the language in which the codex is written and the method of encryption employed is because so little is known about its history; all we know is that the manuscript once belonged to a Hungarian bibliophile called Gusztáv Batthyány (1803–1883) and that he kept it in the town of Rohonc, now the Austrian town of Rechnitz. It is the old Western Hungarian settlement that gave its name to the codex. Batthyány bequeathed the mysterious work to the Hungarian Academy of Sciences in 1838, where it is still kept to this day.

No-one knows who wrote the Rohonc Codex, when exactly it was created or what its purpose was. One of the few clues to its provenance is the paper with which it was made. This seems to have been produced in Northern Italy in the sixteenth century, judging by a watermark it contains, among other things. So far, however, it has not been possible to determine when the paper was actually used to write the codex.

The Rohonc Codex is an intriguing historical document. Its 448 pages have all been penned in an unknown script. Like the Voynich Manuscript, no-one has been able to decipher it yet. We are not even sure if the Rohonc Codex is a book that was encrypted at all or if the script was actually intended to encode its contents; it may, in fact, be the case that we have encountered a script, all knowledge of which has been lost.

Fig. 3: fol. 82v und 83r. The visual system of the manuscript is complex and exhibits
numerous symbols. It gives the impression that the graphical elements may also be
> Enlarge

The question of whether a secret script was used or just a normal script that is still unknown is irrelevant initially – the methods employed to shed light on the codex are the same. If the author did actually intend to ensure confidentiality, however, he may have taken some additional steps to encrypt the contents. Anything is possible in this case – from simple techniques such as inserting meaningless characters to confuse the reader to sophisticated scrambling, for example.

The most important tool for a decoding expert is statistical analysis. In German, for example, the letter E is used most frequently, followed by N, I and S. This frequency distribution is similar in other languages as well. Unfortunately, however, this insight has not led to any revelations regarding the Rohonc Codex. The fact that we do not know which language the codex is written in is a relatively minor problem here, though; the immediate challenge is that the alphabet that the unknown script employs is very long: researchers currently believe it consists of approximately 100 letters that are used frequently. What’s more, several hundred others appear only once or twice in the codex. The possible explanations that have been proposed for this range from a syllable-based script and nomenclator (an alphabet in which some of the letters stand for whole words) to an artificial language. These hypotheses still need to be examined in detail, however.

Fig. 4: fol. 43v und 44r. There are not merely Christian symbols in the codex:
crescents on top of the roofs. > Enlarge

The 87 pictures in the codex have not been able to shed much light on the contents either so far. Most of the illustrations show motifs from the Bible such as Moses on Mount Sinai or the crucifixion of Jesus (fig. 2). Apart from Christian iconography, we find numerous symbols that give the impression that the graphical elements may also be encoded and were only to be understood by a small circle of people privy to the encoding system (fig. 3). The art historians interviewed by the historian Benedek Làng believe it is likely the document was written in the sixteenth or seventeenth century. They also favour the Balkans as the region of its provenance, but add that other areas of Europe may also be possible. A detailed examination of the illustrations by art historians has yet to be carried out.

Consequently, one can only make educated guesses about the codex at the moment. Does it contain a religious text of a heretical nature, which the author encrypted for fear of reprisal by the Church? Or did someone simply want to demonstrate a newly invented script on a religious text? Does the encryption have any particular magical or religious meaning? Or were the biblical pictures only intended to make it appear as though the book was on a completely different subject? Last but not least, is the codex actually only a piece of imaginative writing containing meaningless letters with which the author wanted to impress people?

If we are to find any answers to these questions, then additional research will need to be conducted to decipher the mysterious script in which the Rohonc Codex was written.


Làng, Benedek (2010): ‘Why don’t we decipher an outdated cipher system? The Codex of Rohonc’, in Cryptologia 34 (2010), 115–144.

Schmech, Klaus (2012): Nicht zu knacken: Von ungelösten Enigma-Codes zu den Briefen des Zodiac-Killers. Munich: Hanser Verlag.


Budapest, Hungarian Academy of Sciences
Shelf mark: MS K 114 and MF 1173/II
Material: paper, 224 leaves
Size: 12×10 cm
Provenance: a private collection belonging to Gusztáv Batthyány (1803–1883)

Text by Klaus Schmeh