It is a staple of a vast majority of action and thriller acts from all over the world. The protagonist sits in front of a computer, the surrounding darkness serving as a dramatic prop for the light of the monitor to shine on his weary but intent countenance. The camera pans to show some nonsense gibberish scrolling up until the actor presses some key combinations – and the screen resolves itself into a more understandable (and undeniably vital) string of information. Then the action springs off again. Let’s go little deeper in cipher.
No matter how much media underplays it, the art and science of encoding and decoding is a very meticulous process and very rarely accomplished by just a few keyboard strokes. Sure, it is exciting, but it takes a lot of patience and a cunning mind. The media got one thing right, though – most of the important events in history occurred by the victorious breaking of a certain code or the successful concealment of the same.
The discipline that governs these activities we have described is known as “cryptography”. It came from the Greek word kryptos meaning “secret” or “hidden”, and the suffix graphein which means “writing”. It is basically the act of communicating securely, even in the presence of numerous third parties (which are called “adversaries” – a nod to the Bond-like feel of the activities involved).
Aside from the writing and breaking of codes, cryptography also tackles the different communications protocols – digital rules that determine the behaviour of data exchange and interpretation between two systems – that will let the system evade the intrusion and subsequent influence of the adversaries. In our highly technologically dependent age, this field plays a very important role. It pertains to different aspects of data integrity and confidentiality, information security, data authentication, and lots more. A person skilled in the science of cryptography will need to have prerequisite learning in other fields – electrical engineering, computer science, and applied math among others.
Before the world became too high tech, the word “cryptography” is almost always restricted to “encryption”, or the process of coding a certain message so that only the intended recipients (or those authorized in their stead) will be able to understand its contents. Those onlookers who attempt to capture the data will only receive gibberish. In this sense, the creator of the code will share a sort of “key” or “decoder” that is needed to convert the message back to its original form. This is relatively straightforward – however, the advent of computerization and its application in such field as warfare had revolutionized the process, making it exponentially more difficult as the technology matures further.
Nowadays, the act of creating a code and sharing it with the intended recipient has become obsolete. Most often, mathematical theory and the different applications of computer science are employed. In fact, cryptography has already grown so large in scope that not only do a majority of industries rely on it, but it has made changes in such disparate fields such as the law. This article will be discussing the different aspects of cryptography, tracing its progress from ancient times to the most modern methods that are being used.
Read: History of Cryptography Analysis & Decoding In The Early-Modern Era
As we had mentioned, the very first purpose of cryptography (although the word had not yet even existed then) was simply to hide a message from prying eyes. The application of this was limited to military and political usage. In fact, a majority of people during cryptography’s birth would not even be able to read the non-encrypted message, even if it had been plastered on their bedroom walls – many people of that time couldn’t read! But dealing with educated enemies is a different thing altogether.
Primitive Ciphers
The most “classical” cryptographic technique was called the transposition cipher. This is pretty basic – letters or groups of letters are shifted (“transposed”) according to a preset order. This way, the cipher becomes a permutation or a simple rearrangement of the original text. It may sound simple, but there are actually several different kinds of transposition techniques.
Another simple cipher that originated in the olden times is called the substitution cipher. This is carried out by replacing a letter or a group of letters with another letter or group of letters. For instance, one can replace the letters of a sentence with the letters that come before or after it in the Latin alphabet. The Caesar cipher (also called the “shift cipher”) changes every letter of the message with another one a fixed number of letters down or up the alphabetical order. Encrypting a text using different series of Caesar cipher has also been employed by enterprising cryptographers of the time. This has come to be called the Vigenère cipher, after its supposed father, Blaise de Vigenère. The cipher was stronger and was an early form of what is now called the polyalphabetic substitution method.
Another type of early substitution cipher is called the Atbash, hailing from the Hebrew alphabet. The first letter of the alphabet (alpeh) is replaced by the last (tav), the second (beth) is interchanged with the second before last (shin), and so on. Hence, the name became Aleph-Tav-Beth-Shin, later shortened into “Atbash” (in much the same way that the word “alphabet” came from the first two letters of the Greek alphabet Alpha and Beta).
In history, the earliest recorded use of cryptography came from the Ancient Egyptians. However, experts argue that the carved text on the stone had been created for mere entertainment purposes rather than actually being utilized to conceal information. The ancient Hindu text Kama Sutra advocates the use of cryptography as a means for lovers to communicate discreetly.
Scytale
When speaking of cryptographic implements, one of the earliest may be the scytale, which has been used by the ancient Greeks and Spartans. This is essentially a tool to create a transposition cipher and is simply a cylinder with a strip of parchment or other writing surface wound tightly against it. The implement has been used as a means to communicate secretly in the midst of military campaigns.
Both the sender and the recipient of the encrypted message would need to have a cylindrical piece of wood with exactly the same dimensions – this is critical to the process. The sender wraps the strip of parchment tightly around the cylinder, writing across. The characters in the lines of the message would only be as much as the number of times the parchment has been wound – for example, the parchment could only be wound four times, the line can only contain four letters (one letter per wind). The next letter will have to fall on the next line. When the strip is unwound, the letters would appear to be in a different sequence, and such the message is encrypted. The receiving end would only have to wrap the strip again against the wooden rod to read the message.
This method allows for speed and efficiency while lessening the propensity for mistakes both in the encoding ad decoding processes. Other historians also advance the theory that the scytale was created as the first mechanism that allows for non-repudiation – a proof that the sender was actually the one who did send the message. A person who does not know the specifications of the decoding rod would not be able to insert a false message into the line of communications.
Steganography
The ancients have also created another method of encryption, called steganography. This is the practice of hiding a piece of information within another piece of information or an unlikely vessel. The word precisely means “covered writing” or rather “concealed writing”. One advantage of steganography is that it does not attract attention to itself as an object of interest. Any other secret message, no matter how well coded, will always arouse scrutiny even if it is not broken. However, hidden messages that are made to appear as a part of something else – an image, a block of text, other unlikely cover vessels – will not be discovered unless the recipient knows it is there.
One classic example of steganography in ancient history came from Herodotus, who related the account of a message tattooed on a slave’s shaved head. The hair was allowed to regrow, and the slave was sent to his destination. Shaving the hair revealed the hidden message!
One other steganographic method is known to us today as the “Polybius square”. This groups the letters of the alphabet inside a 5×5 square (with the letters I and J using up the same slot). The letters can be deduced when the rows and columns are given, much like on a Cartesian coordinate system. It is to be noted that this type of encryption system has also enjoyed widespread use in ancient Japan. In their system, however, the words used in the message should be chosen carefully, as two separate decipherments can sometimes be discerned from the same block of encoded text.
Breaking Ancient Ciphers
Basically, all of the ancient ciphers can be easily decoded, even if the person who attempts to crack them does not know the keys with which they are made from. A study of the coded text itself can reveal valuable information about the code that has been used. Frequency analysis, a mathematical study of the group of letters used in a coded block of text, turned out to be a very powerful weapon. The discovery of this tool birthed the first incarnation of the science of cryptanalysis.
Even the Vigenère cipher, strong as it was for its time, had a vulnerability (albeit one that was exposed only as late as 1846). A method called Kasiski’s Examination uses a logical approach that analyzes the string of text, looking for keywords, breaking the string into monoalphabetic substitutions that can then be pried open using frequency analysis. This allows an adversary with only these tools at his disposal to crack even a basic polyalphabetic ciphertext.
Although these ciphers are effective in practice (i.e., in the heat of the war or in the midst of a flash political crisis), any dedicated and informed adversary equipped with newly developed mathematical knowledge would be able to break through the ciphers that the ancients have created like a sword through the wood. The need for stronger cipher system soon became apparent. However, we can rejoice in the fact that these cipher systems have been established as a vital foundation on which cryptography lies. These ancient forms have even survived in the form of children’s puzzles and other similar novelties.
