Posted in History & Literature

Rosetta Stone

In 1799, during Napoleon’s campaign in Egypt, a French officer named Pierre-François Bouchard came across a granite slab a couple of miles from a port city named Rosetta. The slab – about 112cm by 75cm in size – was densely filled with ancient inscriptions on one face of it. But strangely, there were three distinct languages written on the slab: Egyptian hieroglyphs, an unknown script and Greek.

The discovery of this stone sparked immediate scientific interest. Up until this point, no scholar had been able to decipher the Egyptian hieroglyphs. The hieroglyphs had not been used formally for almost 1800 years, so the way to read it had been lost to time. Europe was going through an “Egyptomania” at the time, with great interest in this ancient civilisation. However, little was known about the culture as the ancient texts could not be read.

People quickly noted that there was a strong chance that the so-called “Rosetta Stone” contained the same text in three different languages, which meant that if you could translate one of the languages, then you could decipher the alphabet of the other two. This proved to be true, with the text being a royal decree exempting priests from taxation. Numerous scholars from all over Europe pored over the Rosetta Stone to solve the mystery of Egyptian hieroglyphs.

The first step was to translate the Greek version, as ancient Greek had already been studied in depth by scholars.
Around a similar time, a Swedish linguist named Johan David Åkerblad figured out that the middle, unknown script was Demotic, a cursive script used in ancient Egypt. Åkerblad was able to decipher the Demotic alphabet by comparing it to the Greek script, particularly through comparing names, as both languages were largely phonetic, meaning the characters used to write the name will have the same sounds in the two languages.

The final step – deciphering hieroglyphics – proved to be much harder. It was theorised that hieroglyphs were not phonetic, but ideographic, meaning each letter represented a whole word or concept (similar to Chinese) rather than a sound. If this is true, then it is impossible to decipher the hieroglyphic alphabet just by comparing it to the phonetic Demotic and Greek scripts.

But then, one scholar named Silvestre de Sacy realised that foreign names would have been written phonetically, much like Chinese scripts. This allowed him to zero in to Greek names in each script, such as Ptolemaios, thus creating a skeleton for the phonetic alphabet for both  Demotic and hieroglyphs. Scholars could then use the phonetic reading of hieroglyphs to make more headway into reading the Rosetta Stone.

After 20 years of exhausting research, the Rosetta Stone was finally fully deciphered. The Rosetta Stone is famous because it was the key required to decipher the entire Egyptian hieroglyph system, while birthing the new field of Egyptology. Being able to read hieroglyphs allowed us to better understand the ancient Egyptians’ way of life. Nowadays, the term Rosetta Stone is also used as a symbol of a key to understanding an entirely new field of knowledge.

Posted in Science & Nature

Cryptography: Caesar Cipher

One of the earliest known uses of cryptography can be traced back to ancient Rome. Julius Caesar was well-known for his use of a type of substitution cipher dubbed “Caesar cipher” or “Caesar shift”. The encryption is very simple: shift every letter a certain value down the alphabet (the value is known as the key). For example, Caesar used a key of 3 to encrypt his messages to his general, so the message “ATTACK AT DAWN” would be encrypted into “DWWDFN DW GDZQ” (use the scheme of a=0, b=1, c=2, d=3…).

Although it was an efficient encryption system in ancient times, since then it has been revised to be much more secure. The Caesar cipher has thus been demoted to the preferred code used by children and teenagers for basic decoding puzzles.

Due to the simplicity of the encryption, cracking the Caesar cipher is quite easy with the use frequency analysis, pattern recognition and brute force analysis. Brute force analysis can be used if the attacker knows that a Caesar cipher has been used. If that is the case, the message can be decrypted using every possible key (e.g. 1, 2, 3…) until a message that makes sense is acquired.

Posted in Science & Nature

Cryptography: Frequency Analysis

A cipher is a message that has been encoded using a certain key. The most common and basic type of ciphers are encrypted using letter substitution, where each letter represents a different, respective letter. For example, the message may be encoded in a way so that each letter represents a letter three values before it on the alphabet (e.g. if a=0, b=1… “a” becomes “d”, “b” becomes “e” etc.). This creates a jumble of letters that appears to be indecipherable.

However, the characteristics of substitution ciphers make them the most decipherable type of encryptions. As each letter can only represent one other letter, as long as the key is cracked (i.e. what letter is what), the message and any future messages can be cracked. The most important tool in decrypting substitution ciphers is pattern recognition and frequency analysis.

Frequency analysis relies on the fact that every language has certain letters that are more used than others. In the English language, the letters that are most used, in order, are: E, T, A, O, I, N, S, H, R, D, L, U (realistically, only E, T, A, O are significant and the rest are neither reliable nor useful in frequency analysis).

For example, if Eve intercepted a long, encrypted message that she suspects to be a simple substitution cipher, she will first analyse the text for the most common letter, bigram (two letter sequence) and trigram. If she found that I is the most common single letter, XL the most common bigram and XLI the most common trigram, she can ascertain with considerable accuracy that I=e, X=t and L=h (“th” and “the” are the most common bigram and trigram respectively). Once she substitutes these letters into the cipher, she will soon discover that certain patterns arise. Eve may notice words such as “thCt” and deduce that C=a, or find familiar words and fill in the blanks in the key. The discovery of each letter leads to more patterns and the vicious cycle easily breaks the code.

Frequency analysis is extremely useful as it can be used to attack any simple substitution ciphers, even if they do not use letters. For example, in Sir Arthur Conan Doyle’s Sherlock Holmes tale The Adventure of the Dancing Men, Sherlock Holmes uses frequency analysis to interpret a cryptogram showing a string of hieroglyphs depicting dancing men.

To reinforce this weakness in substitution ciphers, many cryptographers have devised better encryption methods such as polyalphabetic substitution, where several alphabets are used (e.g. a grid of two alphabets – also called a tabula recta).