Cryptography is a system designed to render a text, message or file illegible to anyone who does not possess the correct key required to read it. Its origin derives from the combination of two Greek words: Kryptòs (hidden) and graphìa (writing), which reflect the definition of this technique.
In more modern times, with information travelling at the speed of light across the global internet network, cryptography plays a crucial role. Protecting communications, the exchange of files and highly sensitive data is of fundamental importance and that has led to specific encryption algorithms being developed.
When was cryptography first invented and how has it evolved?
The need to hide messages from prying eyes has been part of human life since time immemorial. The earliest evidence of cryptographic systems can be traced to the writings of Plutarch. The Ancient Greek biographer and philosopher told of a simple but efficient system used by the Spartans to send secret messages in his work ‘Life of Alexander’.
A wooden stick of a specific length and diameter was wrapped in a strip of leather, onto which the message would be engraved. Once the strip of leather was unrolled, the message became illegible and could only be recomposed if the leather was wrapped around a stick of the exact same length and diameter as the original.
In more recent times, with information in digital form and the now imperative need to guarantee the privacy and security of that data, highly sophisticated mathematical algorithms are used. These complex calculations are designed to mask the message, rendering it fully legible only to those with the right key, exactly like the Spartans’ wooden stick.
How modern cryptography works
The primary objective of modern cryptography is to protect data transmitted via the internet or in other ways. In order to do that, highly complex cryptographic algorithms are used to transform a sequence of characters in accordance with the values of a secret encryption key.
The strength and complexity of this key indicate the security level of the entire cryptographic system used. Generally speaking, there are two distinct types of cryptography: symmetrical encryption and asymmetrical encryption.
The first system uses a single encryption key, which is identical for the sender and the recipient. If, however, two separate keys are used, then asymmetrical encryption is adopted, where the encryption key is public, but the decryption key remains secret and private.
Both techniques have pros and cons, which should be carefully considered when choosing between the two protocols. Symmetrical encryption is fast and very simple to implement into various systems, because it is based on a series of algebraic calculations repeated multiple times.
The AES (Advanced Encryption Standard) is the most common example of symmetrical encryption and there are several different versions of it available, according to the desired level of security. These are identified by the blocks of bits used: 128, 192, or 256 (the most secure).
Asymmetrical encryption however, uses keys which are mutually interdependent, one being public, the other private. This system makes the encryption even more secure, but at the same time slow and laborious to implement.
An interesting breakthrough was achieved with the RSA (Rivest, Shamir, Adleman) system, invented by three students of MIT in 1977. Instead of masking the data directly, this technique uses symmetrical encryption and then encrypts the key of the latter asymmetrically, making the decryption process much quicker.
Cryptography is in constant evolution and there are frequent changes linked to the latest technologies. There are currently systems based on grids, quantum physics, hash codes and many more.
Translated by Joanne Beckwith