The story of the events at Rennes-le-Chateau has been given by Lincoln (1-3),
Fanthorpe (4), Mizrach (5), Nullens (6), de Sede (7) and others, and tells of
parchments discovered at the Bibliotheque Nationale by de Sede and Lincoln bearing
coded messages, which were allegedly found by Sauniere and his workmen in a
wooden tube, or a bottle, during the restoration of the parish church. The key to the
decryption of the messages was leaked to de Sede, and thence to Lincoln, and involved
the use of the epitaph on the tombstone of Marie de Blanchefort in the churchyard at
Rennes-le-Chateau as a keyword in a well-known method of encryption invented by
Vigenere. The message after decryption is only partly comprehensible, but hints at
hidden treasure and ways in which it might be found. A BBC TV Timewatch
programme by Lincoln (3) in July 1996 significantly enlarged our knowledge. The
parchments, we learned, were deposited at the Bibliotheque Nationale by two rogues,
Pierre Plantard and Philippe de Cherisey, and the latter has made a written claim to be
their author. They are currently in the possession of a writer, Jean Luc Chaumeil, who
received them from de Cherisey. He also possesses a pamphlet called Stone and Paper,
which surely should be made public, written by de Cherisey in which, we are told, he
gives an explanation of the composition of the parchments, and how they can be
decoded.
The usual account given by Lincoln, and presumably obtained from de Cherisey, of the
composition of the document often called the Second Parchment, implies the
performance of a number of steps of cryptography carried out by its author. We here
go through these steps in the order in which a cryptographer would take them, rather
than the order of decryption described by Lincoln and Fanthorpe, pointing out several
features which are so far unexplained, which cast serious doubt on the claim of de
Cherisey.
1) We assume that the plaintext of the encryption is the familiar text of 128 letters,
starting “Bergere pas de tentation...”, which we will refer to as berg. This is the
message, which, it is supposed, the author wished to convey to some recipient. For no
reason which has been discovered, except possibly the generation of mystification or
amazement, he chose to make his message an anagram of the letters of the epitaph of
the Marie de Blanchefort epitaph.
2) He starts the encryption process by changing the order of the letters i.e. he uses a
Transposition Cipher. The reordering is achieved by means of a solution to the old
problem posed in 1720 of the “Knight’s Tour”, a tour visiting all the squares on a
chessboard once, and once only, using only Knight’s moves. The tour used appears to
be a beautiful adaptation of the first published solution by de Moivre (1667-1754). The
plaintext is written on a chessboard, starting at the start of the tour. After 64 letters,
the text is continued on another chessboard carrying the same tour but drawn upside
down. The next array of letters, starting xnls, is obtained by reading across the boards,
starting in the top left hand corner.
3) According to the story given to Lincoln, he next uses a Substitution Cipher called
the Tableau de Vigeneres (1586). This requires the selection of a keyword, and he
chooses the whole of the epitaph of Marie de Blanchefort written backwards. This is a
surprising choice because the keyword has the same length as the text, sufficient to
ensure a lavish degree of concealment.
The Tableau de Vigeneres lays down two sets of rules, one for encryption and one for
decryption. Our imagined author is supposed to be encrypting his message, but he uses
the rules for decryption.
4) If the author in fact used the Tableau de Vigeneres, it is necessary to assume that
he followed the operation by taking a step up the alphabet of one letter to arrive at the
arrays presented. It seems likely that he used an alternative procedure, sometimes
called the “position value” method, in which the letters of the alphabet are replaced by
the numbers from 1 to 26 (or 25). The numbers for the text and keyword are added
together (for encryption) and then translated back to letters. It turns out that this
avoids the need for the otherwise unexplained step up the alphabet.
The fact that the keyword is made up of the same letters as the text leads to an
anomaly in the next array of letters, starting jrin, namely, 14 appearances of the letter
z.
5) When the decryption was first demonstrated by Henry Lincoln in a Chronicle
programme on BBC TV in 1979, a 26 letter alphabet was used, although an 18th
Century origin was assumed, and the letter w was not then part of the French alphabet.
When this contradiction was pointed out, Lincoln went back to his source, presumably
de Cherisey, for an explanation. He was told that this was an unimportant detail, and
all that was necessary was to insert another step along the alphabet, and all would be
well. When tested, this is found to be untrue. The work must have been carried out
with a 25 letter alphabet, either because the author was working in the 18th Century,
or because he was sufficiently well informed to be able to behave consistently.
6) The final step is another use of the Tableau de Vigeneres, together with a step up
the alphabet, or alternatively, a use of the “position value” method, with the enigmatic
keyword mortepee, which is again obtained from the epitaph of Marie de Blanchefort
by selecting letters which are misplaced, or otherwise unusual. Again, this step, which
we are describing as the final step in the encryption is a step which would
conventionally be called decryption. At this stage, the array of letters, starting vcps, is
an array which could reasonably be a random selection from the alphabet, and is
therefore perfectly secure from attack by straightforward statistical analysis. The 14 z’s
of jrin have been eliminated, though there are now 10 t’s. This may be at least partly
because mortepee is not a very effective keyword, having three of its eight letters the
same.
The puzzles enumerated above do not seem to have been understood by de Cherisey,
who, nevertheless, claims to be the author of the parchments. A fuller account of this
work will appear shortly on the internet.
1. Lincoln, H. The Holy Place, Jonathan Cape, London, 1991
2. Lincoln, H. BBC TV ‘Chronicle’ 1979
3. Lincoln, H. BBC TV ‘Timewatch’ 1996
4. Fanthorpe, L. Rennes-le-Chateau, Bellevue Books, 1991
5. Mizrach, S. http://www.clas.ufl.edu/anthro
6. Nullens, G.C.H. http://www.isabel-uk.com
7. de Sede, G. Rennes-le-Chateau, Editions Robert Laffont, Paris, 1988