Cryptography, just like the automobile industry, has undergone huge advancements over the years.

Despite these dramatic changes, we don’t identify gasoline vehicles as classic automobiles or electric vehicles as modern automobiles. But we do make that distinction in the case of cryptography—and rightly so—as we’ll discuss in the following sections.

## Classical Cryptography

Cryptography strategies and methods used to convert plain text into cipher text without the use of technology are known as *classical cryptography*. Cryptography is commonly defined as “an art of writing hidden messages”—and classical cryptography was indeed an art. There were no defined methods or standard techniques to create a cipher text. People needed special interests or hobbies in creating cipher text. The more creative a person is, the stronger the cipher message. Classical cryptography was primarily dependent on substitution ciphers. Every ciphering technique from Vatsyayana, Caesar, and Vigenere to the German Enigma machine, used one or another form of substitution technique.

Classical cryptography had several limitations:

- Classical cryptography was heavily dependent on substitution ciphers, which were very vulnerable to frequency analysis. Most codes were cracked relatively easily. The Vigenere cipher was uncrackable for almost three centuries, but eventually the cipher was cracked. Even the Zimmerman Telegram and Enigma cipher texts were broken.
- Successful decoding of the message relied on the fact that the substitution mechanism, the code book, or other methods, was shared before the communication took place. The Vigenere cipher was the first one to use some sort of key or keyword in the encryption process. Every cipher before that was largely dependent on the secrecy of the method (the algorithm itself). Once the method or the code book was intercepted, there was no secrecy.
- Another limitation of classical cryptography was its inability to scale. Classical cryptography wasn’t designed for large amounts of data. Most of the processes and computations were performed manually in classical cryptography. Manual processing limits the amount of data that can be handled, which restricts the scalability.

## Modern Cryptography

After World War II, technology started to influence every part of our lives, and cryptography couldn’t escape. The use of the latest technology and computing power changed the tide from classical cryptography to modern cryptography. In modern cryptography, messages aren’t sent on horses, and keys aren’t exchanged via pigeons. The use of computing power allowed modern cryptography to use advanced mathematical algorithms to secure not only communication but also data and information at all stages of life.

Modern cryptography took off after the release of DES by NIST in 1977. That was really a turning point in the history of cryptography.

One of the major differences between classical cryptography and modern cryptography is its impact on our lives—classical cryptography was limited to military use while modern cryptography is everywhere—from banking to shopping and from working to vacationing. Almost anything you do now, you have to experience the magic of modern cryptography—and without even realizing it. It may be time to rename *modern cryptography *to *everyday cryptography*!

Although the dictionary definition of cryptography still defines it as “an art of writing hidden messages,” modern cryptography isn’t an art anymore. It’s an exact science. It uses complex mathematics and is very difficult, if not impossible, to crack.

Modern or everyday cryptography has several advantages:

- One of the prime advantages of modern cryptography is its seamless integration. Users never even realize that when you start a car, you encrypt and decrypt codes multiple times or when you enter a password, you use cryptography.
- The speed at which modern cryptography works is the second advantage. Thanks to the latest technology and computational horsepower available to us, even the most complex algorithm runs in a microsecond.
- Modern cryptography protects data in communication, in storage, in applications, in the cloud, and in Internet of Things (IoT) devices. The reach is mind-boggling.
- Modern cryptography offers a very secure key exchange mechanism using key exchange algorithms, which allow for the exchanging of keys without the sender and receiver physically meeting each other.
- Modern cryptography not only offers confidentiality of the data but also offers integrity, authenticity, and nonrepudiation.
- Modern cryptography thrives on public key infrastructure (PKI). Generation and verification of digital certificates are vital to the success of modern cryptography.

Like every coin, modern cryptography also has another side. The challenges of modern cryptography are as follows:

- Modern cryptography is heavily dependent on computational power, and, as a result, it can also be easily cracked with that power. Quantum computing can potentially create risk if we don’t upgrade our encryption algorithms.
- Hackers can use this seamless modern cryptography and generate various attacks, such as ransomware.

## What Is a Cryptography Algorithm?

Modern cryptography involves extensive mathematical computations. An *algorithm *is a process of executing mathematical computations in predefined steps. The software and hardware designed to perform these computations are executed with great computational power.

Modern cryptography, unlike classical cryptography, is heavily dependent on the secrecy of the encryption key. In classical cryptography, it was necessary and very important to keep the algorithm secret. If the attacker knew the algorithm or the method of encryption, the attacker could easily decrypt the message. The concept was known as security through obscurity (STO). The encryption cipher or algorithm was shared with only those who needed to encrypt or decrypt messages. For example, Germans needed to guard the code book and the design of the Enigma machine. However, in modern cryptography, only the encryption key needs to be kept confidential.

** **

## Kerchoff’s Principle

What we just learned is known as *Kerchoff’s principle*. Kerchoff stated that the cryptosystem should be secure even if everything about a cryptosystem is known except the encryption key. Kerchoff was the first to introduce this concept in the late 19th century. Classical cryptography laid a foundation, but modern cryptography made it possible to secure our world.

Learn more about computer security on this page.

Editor’s note: This post has been adapted from a section of the book *Modern Cryptography: The Practical Guide *by Sandip Dholakia.

## Comments