Follow The Clues

Jamie Theakston with the Poisoned Chalice

• The Cryptex
• Rotogravure
• Steganography
• Cardano Grille
• Fibonacci Sequence
• Book code
• Pinprick or puncture code
• Hidden messages in art
• The Gordian Knot
• Indian spy methods
• Hand symbols
• Hieroglyphs
• Maya glyphs
• Frequency analysis
• Pigpen code
• Quipus
• Della Porta's cipher
• Mary Queen of Scots' cipher

The Cryptex

The cryptex was made famous in Dan Brown's book The Da Vinci Code. A portable vault to hide secret messages, it can only be opened by entering the correct sequence of letters or numbers. Like a bicycle combination lock, it is made up of revolving barrels, which only open when lined up correctly.

The contestants have to crack a number sequence to find the combination code to a cryptex, which they find in the birth room of James VI of Scotland (James I of England). The numbers are not actually a mathematical problem at all, but represent the line of Stuart kings and queens. The Stuarts ruled Scotland during the period of Tudor ascendancy in England, and finally took the English crown on Elizabeth I's death in 1603.

In the case of the cryptex featured in James's birth room, the answer is to be found in his title – James the sixth of Scotland. The clue beside the cryptex relates to the line of Stuart kings and queens before him and their numerical titles.

Rotogravure

In Venice, in the first episode, the teams find ink, paper and some wooden scrolls. But there's nothing to print with. Then they see that the markings on the wooden scrolls have a pattern. They are secret rotogravure printing presses: the raised relief must be coated in ink and rolled across the paper. These were used by explorers and spies to carry information securely over long distances, since paper maps or messages could easily have been destroyed.

Venice expressed its cosmopolitan character most clearly in the field of printing. In the first few decades after this new art had been introduced to the city in 1469, Venice was the most important centre of book production in Europe, with 100-150 presses producing books not only in Latin and Italian, but also in Greek, Hebrew, Armenian, Arabic, Czech, Croatian and Serbian.

Steganography

Steganography means concealing hidden messages so that only the intended recipient knows of their existence. In Venice, the teams find two wax balls which represent an ancient form of steganography that explorer Marco Polo would have witnessed in China.

To find the code, the contestants crack the outer wax seal; inside they find a ball of silk wrapped tightly around the secret.

Cardano Grille

In San Gimignano, the teams have to open a box that has a combination lock invented by the great Renaissance mathematician, gambler, inventor and astrologer Gerolamo Cardano. It is said he committed suicide in 1576 in order to fulfil his own astrological prediction of his own death date. He also invented the Cardano Grille , a cryptographical tool.

Fibonacci Sequence

The teams discover a series of numbers. They need to work out the pattern in order to open the combination lock. They realise the numbers are part of the Fibonacci Sequence discovered by Fibonacci, also known as Leonardo of Pisa. He has been described as the 'greatest European mathematician of the Middle Ages' and his work still fascinates academics today.

The Fibonacci sequence (1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 . . .) occurs throughout nature, art, music and mathematics. Each number in the series is produced by adding together the two previous numbers, so that 1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5 and so on.

Book code

Book codes, one of the oldest forms of cryptology, are simple to set and decipher – but not easy to break.

The code setter and the code breaker work from exactly the same text. The code setter counts from an agreed starting place in the text to find the required letter. The number of places is then the code number.

So for example, if the text is 'The Search' and the code is 3, then number 3 = the letter E, 4 = S and 6 = A.
CAR would therefore be shown as 8 6 7

This is a great way to send secret messages because anyone who wants to crack the code has to know the agreed text and starting place. This type of code is often used as a plot device in spy dramas and terrorist thrillers, where characters carry what appears to be an ordinary book but which is, in fact, their means to cracking a secret code.

Pinprick or puncture code

At Carcassone the teams are given a piece of medieval text. At first they attempt to translate it – a tough job, since it is written in Occitan, form of ancient French spoken in the Carcassonne region.

But the way to crack the code was to lift the paper to the sky and see that there were minute holes underneath specific letters, which make a word. This is called a 'puncture code' or 'pinprick code'. This is a quick way to send a code but it has the disadvantage that if the holes are spotted, it is easily decoded.

In the Victorian era, postage was expensive but sending a newspaper was free. People began to use pinpricks to spell out a message on the front page of a newspaper, so that they could send it for free instead of paying postage charges.

This form of code evolved through history into early computers which used punched holes to operate machines. Early 20th century calculators still using punched out information to collect data.

Hidden messages in art

The practice of hiding messages or images behind paintings dates back to the Renaissance. The life of Renaissance artists was difficult. They were at the whim of their patrons and were forced to agree with them or suffer the withdrawal of the patronage. Rather than compromise their often very controversial ideas, artists would hide references to their opinions underneath their paintings.

For example Leonardo Da Vinci was forced to cover up controversial images in his Adoration of The Magi so as not to offend the monks who had commissioned it.

The Gordian Knot

According to a Phrygian legend, an oracle at Telmissus decreed that the next man to enter the city driving an ox cart should become their king. Midas, a poor peasant, happened to drive into town the very next day on an ox cart and was declared king. In gratitude, he dedicated his ox-cart to Zeus, and tied it to a post with an intricate knot. An oracle prophesied that the person who untied the knot would become the king of Asia.

A century years later Alexander the Great, who was known for his territorial ambitions, rode into Phrygia to try to undo the knot. When he could not untie it, he simply took out his sword and cut through it (the so-called 'Alexandrian solution') and went on to govern India.

To this day the expression 'cutting the Gordian knot' is used as a metaphor for using a bold stroke to solve an intractable problem.

Indian spy methods

The teams have to use Dhaqranamatrka, an ancient method of memorising secret messages used by spies, which originated in Jaipur. 'Dharana' means to remember, and in ancient India Dhagranamatrka was a highly valued skill, used before printing to prevent information from falling into enemy hands.

Espionage was so prevalent within the administrations of Indian government that it has been euphemistically called the world's 'second oldest profession'. Spies were said to hide all over the cities in order to pick up incriminating gossip, and they were integral to the political institutions of ancient India.

The institution of espionage in ancient India, like modern times, required secret agents to work under some kind of cover to preserve secrecy. The most common disguises were those of 'merchant, artisan, wandering minstrel, artiste, cook, barber and shampooer, bath and toilet attendant, deaf, dumb, eunuch and prostitute'.

Spies would inform the King about the behaviour of their wives or concubines, and there are many Indian stories of kings being poisoned by spies or using spies to poison their rivals.

Women, particularly those engaged in prostitution, were said to be effective tools of espionage and were employed as Visakanyas (poison damsels).

Hand symbols

The team crack an ancient form of communication called Nirbhasa, in which fingers are used as a means of communication – the fingers themselves stand for the consonants and the finger joints for vowels. People point to individual knuckles on each hand to spell out words.

These hand signs are said to still be used by traders in some parts of India.

Hieroglyphs

Although hieroglyphics are not technically a code, the skills used to decipher them are the same as those used by code crackers. Hieroglyphics are made up of more than 700 symbols, some of which are phonetic and some a direct representation of the image they depict.

The earliest form of writing, hieroglyphs are believed to date back as far as 3,000BC and were prominently displayed on pyramids and monuments. Their use died out following the spread of Christianity, when they were outlawed by the church. The ability to read hieroglyphics was lost as other languages and forms of writing became dominant.

Early attempts to decipher hieroglyphics foundered because it was assumed that they were picture writing rather than phonetic signs. The discovery of the Rosetta Stone, carved in 196BC and rediscovered in 1799, provided the key to translating this Ancient Egyptian writing.

The Rosetta Stone resembles a cryptanalytic crib – it contains the same piece of text written in three different ways: Demotic, an Ancient Egyptian writing system, Greek and Hieroglyphs. This provided a breakthrough in understanding the ancient language of hieroglyphs.

The 19th century brought a race amongst European scholars to become the first person to decode Hieroglyphics. Englishman Thomas Young was the first to correlate the hieroglyphs with their sound values but he did not complete his research. Frenchman Jean Paul Champollion made it his life's work to crack Hieroglyphics – an obsession which lasted over 15 years. His ingenious work was finally published in 1824, giving him a well-earned place in history.

Maya glyphs

When the English were entering the Dark Ages, the Maya civilisation was relatively advanced. The Maya, who flourished between about 250AD and 900AD, perfected the most complex writing system in the hemisphere, mastered mathematics and astrological calendars of astonishing accuracy, and built massive pyramids all over Central America, from Yucatan to modern Honduras.

Maya writing is one of the world's most complex writing systems. It is extremely visual, with hundreds of unique signs or glyphs in the form of humans, animals, supernatural creatures, objects, and abstract designs.

These signs are either logograms (to express meaning) or syllabograms (to denote sound values), and are used to write words, phrases, and sentences. In fact, the Maya could write anything that they could say.

The Mayans used a base twenty system and used a symbol for zero.
Below are the Mayan numerals for zero to nineteen.

There was grouping by fives within the first twenty numbers. When they had one numeral over the other, the top numeral indicated the number of twentys and the bottom numeral the number of ones.

Frequency analysis

Frequency analysis is one of the cornerstones of code breaking. If you know which is the most commonly used letter of the alphabet, you can begin to crack the code.

Frequency analysis is based on the fact that, in any given stretch of written language, certain letters and combinations of letters occur with particular frequencies. Moreover, there is a characteristic distribution of letters which is roughly the same for most samples of that language.

For instance, in English the most common letter is E, followed by T. So if you find a three-letter word beginning with T and ending in E, the chances are that the middle letter will be H.

Using this system, you can figure out further letters and crack the code.

Pigpen code

In Peru, The Search teams have to decode symbols on an Inca cloth, using a chakana – a stepped Inca cross – as the basis of a letter grid. Each square in the grid has a unique shape and represents a letter in the alphabet.

This type of code is called a pigpen code because of the shapes it creates. In the 16th century, Freemasons used this type of code to keep their letters private.

The cipher does not substitute one letter for another; rather it substitutes each letter for a symbol. The alphabet is written in the grids shown, and then each letter is enciphered by replacing it with a symbol that corresponds to the portion of the pigpen grid containing the letter.

Quipus

The Incans controlled an area that was larger than the Roman Empire. They had no written language but used a simple code, called Quipus, to control their empire.

In essence this is an accounting system which uses knots in a rope, like a primitive spreadsheet system – the Excel of its time!

The quipu is a series of coloured, knotted strings. The type of knot indicated a number, and the position of the knot signified units of 1, 10, 100 or more. All the cords hung from a main string, and their positions and colours signalled what was being counted – gold, corn or other goods.

Della Porta's cipher

When The Search teams discover a portrait of Queen Elizabeth I at the Old Royal Naval College, they rip the back off the painting to reveal a sheet of code.

This code is known as a digraphic substitution cipher and was invented by Italian Renaissance master of cryptography, Giovanni Della Porta.

A digraph is a combination of two letters to represent a single sound such as 'th' in the, and 'gh' in tough.

Della Porta's cipher is a substitution cipher but each symbol represents two letters.

View complete grid

Della Porta's grid (see example) is a crib to the symbols. You find the symbol and then read the letter along the X-axis and the letter along the Y-axis. So in full it would be 26 rows across and 26 rows down.

In his book, De Furtivis Literarum Notis, Della Porta proposed such a system, with a 20 x 20 tableau (for the 20 letters of the Italian/Latin alphabet he was using) filled with 400 unique glyphs. However the system was impractical and was probably never actually used.

The earliest practical digraphic substitution was the so-called Playfair cipher, invented by Sir Charles Wheatstone in 1854. It was in military use from the Boer War through World War II. In this cipher, a 5 x 5 grid is filled with the letters of a mixed alphabet (two letters, usually I and J, are combined). A digraphic substitution is then simulated by taking pairs of letters as two corners of a rectangle, and using the other two corners as the ciphertext.

Mary Queen of Scots' cipher

When Mary Queen of Scots was held at Chartley Hall, Staffordshire, she wrote all her letters in code in the hope that she would be able to send messages that would not be intercepted by her archrival, Queen Elizabeth I. She wrote using 23 letter substitutions and 36 code signs for words and phrases. This blend of code words and cipher is known as nomenclator.

Her efforts turned out to be pointless. Her correspondent Gilbert Clifford was a double agent. English spymaster Francis Walsingham routinely intercepted her letters because his network of spies and agents infiltrated all of Mary's court. Her code was broken by Walsingham's school of spies and code-breakers.

The letters proved to be Mary's downfall – they indicated a plot against Elizabeth and she was executed. Walsingham's spies cracked Mary's code by using frequency analysis.

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