The concept of cryptography using more modern means actually picked up in a continuous flow from the remarkable case of the German Enigma machines. Aside from the bombe (which was first made by the Polish), the Allies, especially the British, created an all-new machine that did not utilize turning rotors and other physical relay mechanisms – in short, purely digital mechanisms that are also considered forefathers of the same computer systems that brought you here. Let’s move towards a brief history of cryptography.
The British called it the Colossus, a programmable machine that was mainly employed against the German Lorenz cipher (which was generated using rotor stream cipher machines akin to the Enigma). The Colossus was the brainchild of engineer Tommy Flowers of the Government School and Cipher School (GS&CS), utilizing Alan Turing’s ideas regarding the use of probability in the science of cryptanalysis. Turing himself was instrumental in the creation of the bombe and created one of the very first renditions of the general-purpose computer with his Turing Machine.
The Colossus’ first model, the Mark 1, was first deployed against the Germans in February 1944. Within the same year, another model, the Mark 2, was released. The latter version used a development called the “shift register” to give a speed boost of almost 5 times the original. A total of 10 versions were working for the Allies by the end of the war. However, the entire system was only recreated last 2007, as the machine and its blueprints were destroyed after the War to maintain secrecy.
Because of Colossus’ development, the Computer Age of cryptography was ushered in. As the first digital creation was used to decode, future machines were also used to encode data. A new and greatly significant development happened when cryptographers gained the ability to, using the language of computers, encode any type of character that can be represented in a binary form. This is in contrast to previous types of encryption techniques that can only encode texts in a written language.
The age of linguistic cryptography is over, and binary bit systems have now taken a central role. Even nowadays, the process of encrypting information has remained miles ahead of attempts to decrypt them. The supposition that a good cipher (in addition to its previously mentioned characteristics) should not take up to many resources to make is already universally accepted. This makes breaking these ciphers an effort much harder in proportion, immensely more than that of any classical cipher, and when applied to a large-scale event makes it almost totally impractical.
In the mid-1970s, open academic inquiries into the nature of cryptography were born. More recently, private institutions have delved into the subject, a province which was almost exclusively held by the government during wartime years and the opening years afterwards. IBM personnel were responsible for the creation of the Data Encryption System which later on became a standard of the US government.
The First Key Exchange Systems
In 1976, Whitfield Diffie and Martin Hellman, both American cryptographers, created the “Diffie-Hellman Key Exchange” system, a method of exchanging cryptographic keys that were one of the first practical examples of key exchange – the process by which keys are exchanged and kept secret between the sender and the receiver of the message. This process brought to light the “asymmetric” method of encryption, also called “Public-Key Cryptography”. This has been hailed to be the most revolutionary idea in the field of cryptography since polyalphabetic substitution was invented in the Renaissance.
The Diffie-Hellman system allows the two parties to exchange keys over an insecure public network. It uses an application of modulo algebra at its core. Essentially, the system works through the use of a shared secret between the two parties. It is a type of asymmetric key that uses two mathematically related keys – one public, and one private.
It is said that this same scheme has been invented within the walls of the British Government Communication Headquarters a few years earlier, although it was kept classified. The exchange system is an example of anonymous or “non-authenticated key-agreement protocol”, although it has been used as a basis of different varieties of authenticated protocols. Such anonymous exchanges are basic and yet vulnerable to attacks by adversaries trying to sabotage or corrupt the system with their own messages, without both ends of the line knowing of this activity.
To safeguard against these “man-in-the-middle” attacks a password or a similar implementation may be used. The use of a trusted third party on which both the sender and receiver rely on for security and authentication is also widespread – the basis of public-key cryptography, which is still evident nowadays as a means to secure web traffic and Internet protocol communications. More information about these aspects will be revealed later.
The First Cryptosystem
In keeping with the participation of private entities in the field of modern cryptography, the “RSA Cryptosystem” was published in 1977 by MIT researchers Ron Rivest, Adi Shamir, and Leonard Adleman (the name “RSA” was taken from their last names). This is one of the first practical public-key cryptosystems, which provide a suite of algorithms needed to encrypt and decrypt a certain plaintext message. Breaking the RSA encryption is such a momentous task that it has been dubbed the RSA problem.
Users of the RSA system will publish the product of any two large prime numbers, together with an auxiliary value. This will stand as the public key. The prime factors will be kept secret, forming a sort of “private” key. Technically, anyone can use the public key to create encrypted messages – however, if the key is large enough, only those who know the prime factors can decode it. This system banks on the complexity of factoring the product of the two prime numbers, known in the field of mathematics as the “factoring problem”.
In fact, it is a prevailing mentality in the field of cryptography that the harder the mathematical problem that is needed to be solved in order to break the code, the more secured a piece of information is.
History of Cryptography Thus Far
So far, we had discussed the different developments that made substantial changes in the cryptographic field. These things are important for any beginner cryptographer to know, as it would be essential to gauge what developments would be to come in the future. For example, the advances in computing power had made cryptographic systems more vulnerable than ever to “brute-force attacks” (also called “exhaustive key search”). This is the act of systematically looking at all possibilities of keys, passwords, and other variables until the correct decoding is found.
As such, this is extremely intensive and may include travelling the depth and width of the cryptographic search space (the possibility of all keys). It is not so common (as rarely would anyone go through such pains), but nevertheless an imminent threat, as specific hardware and software had actually been produced for this sole task. As a countermeasure, key lengths are also expanding.
Another threat (though not as imminent), is the onset of quantum computing. This is generally the harnessing of an atom’s computing power (relying on 16 electron valence states instead of two binary values) to perform computations. Though computers this powerful are still quite far off the horizon, components of quantum computing are fast being invented. Cryptographers of late are already studying countermeasures to deal with this new threat.
As we have discovered earlier, prior to the age of technology (and even well within its opening years), the focus of cryptography stood on lexicographic and linguistic patterns. But the plane has shifted towards the use of mathematics (computational complexity, information theory, combinatorics, statistics, number theory and abstract algebra) to encode and decode, with the substantial application of computer sciences.
As a branch of engineering (a facet that most people do not recognize), cryptography is unique in being the only one that is required to deal with active, intelligent forces that provide opposition to it (often in a malevolent way) – others deal only with natural forces, none of whom seek to dismantle their works.
