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Cryptology is the science of encrypting readable information (known as the “plaintext”) into unintelligible information (known as the “ciphertext”) in order to prevent the information from being discovered by others, and also figuring out how to turn the ciphertext back into plaintext. Cryptology consists of two main parts: cryptography and cryptanalysis. Cryptography is the practice of implementing various algorithms, or methods, to encrypt information in order to conceal it. It is used in many ways; for example, encrypting your connection to a website in order to prevent others from discovering sensitive information, such as credit card numbers and passwords. Cryptanalysis, on the other hand, is the practice of cracking the ciphertext and figuring out what the plaintext was. Cryptanalysis can be used for both good and bad purposes. It is, of course, necessary to use cryptanalysis to ensure that an algorithm is effective and secure. However, it can also be used in hacking. For example, hackers can obtain sensitive information online if the encryption algorithms used by the website are not secure, or if the hacker is able to obtain the keys used to encrypt the data; but we will elaborate on that later.
Cryptology has existed for a long time. The first example of cryptology, ciphertext carved into a stone, dates back to 1900 BCE in Ancient Egypt. It has become much more advanced with time. Back in ancient times, ciphers were extremely simple, and looking at it now, incredibly easy to decipher. For example, many very old ciphers were based on simply shifting letters x amount of times in the alphabet, so you might be able to figure out the key based on, for instance, seeing a one letter word in ciphertext (which in plaintext is most likely either “I” or “a”), and use that key to decipher everything else. Now, we use such complicated ciphers that you need computers to decipher them, and very powerful computers at that.
The government started to make cryptology a secretive practice after World War I. This was because the US realized that they were going to be able to manipulate all different ciphers and create new ones, for war tactics and other classified operations. The United States started to use different type of ciphers during different wars to exchange many different messages without the enemy realizing, and they faced no threat of hacking or other opposition because computers were expensive at the time, and were possessed only by very, very rich people, the government, and some other institutions. It returned to the so called common people in a sort of renaissance when computers became more available and when demand for encryption increased due to huge changes in the ways America communicated. The increase in demand for cryptography was driven by tre people’s interest, and people required a safe way to make money transactions and secure trade secrets. Digital communications, such as major companies creating software for phones, laptops, and computers, were obviously in need of types of encryption. Modern cryptographers emphasize that security should not depend on the secrecy of the encryption method, only the secrecy of the keys. The secret keys must not be revealed when plaintext and ciphertext are compared, and no person should have knowledge of the key.
Modern algorithms are based on difficult problems that humans mostly can’t do without extreme difficulty, like finding the prime factors of huge numbers. Most algorithms now are done by computers, and in most cases are implemented in computer software. The government doesn’t want them in the wrong hands during a war. When a cipher becomes outdated, or it is exposed, people publicly announce the cipher and its code, making it not possible to use during war. So people use the exposed cipher for commercials and other everyday uses.
Cryptology greatly affects our daily lives. It has many everyday applications. Some of these applications are online encryption and digital currencies. You probably know of these already, and probably use some or both of those examples. However, you might not know how the cryptology behind these examples works, since it is an automated process hidden behind the scenes.
Online encryption is very important in our everyday lives. It ensures our security while on the internet. If it wasn’t for encryption, our passwords, credit card numbers, social security numbers, and other personal information could easily be accessed by hackers and used for nefarious purposes. However, encryption makes this data unintelligible even if it is accessed, and with modern encryption algorithms, it is extremely difficult to decrypt the encrypted information. Now, how exactly does online encryption work? There are two main categories of online encryption: symmetric-key encryption and public-key encryption.
Symmetric-key encryption is when the two computers that are exchanging information need the same key in order for both sides to be able to encrypt and decrypt messages. The first major symmetric-key algorithm was the Data Encryption Standard (DES), which was developed in the 1970’s by IBM. This algorithm used a 56-bit key, which means that the keys are 56 bits, or 7 bytes. However, this algorithm is no longer used because computers can break the data with “brute force”. Brute force is when a computer tries every single possible key to see which key is the real one. Even though there are 70 quadrillion possible combinations that might be the right key, some computers today are powerful enough to find the DES key with brute force. So, now we have the Advanced Encryption Standard (AES). The AES uses 128-, 192-, or 256-bit keys, which is, of course, much more secure. It means that the keys are 16, 24, or 32 bytes. For the smallest of these keys, the 128-bit, there are over 300 decillion possible keys! (That’s 300 followed by 30 zeros!) AES is extremely secure and has never been broken before.
Public-key encryption, also known as asymmetric-key encryption, is another category of encryption algorithms. Rather than having the same key used by both sides, like in symmetric-key encryption, public-key encryption uses two keys: a public key and a private key. Public keys can be seen by any computer communicating with you, while private keys are kept secret and known only by your computer. The public keys are used to encrypt data, and the private keys are used to decrypt data. For example, let’s say Alice sends Bob a message. Alice will use Bob’s public key to encrypt the message, and Bob uses his private key to decrypt the message. This means only Bob can read the message, and any hackers would need the private key in order to decrypt it. You might be wondering, can’t you figure out the private key based on the public key? Well, of course it is possible, but extremely difficult. The public key is the product of two large prime numbers. The private key consists of these two prime numbers. It is enormously difficult to find the prime factors of very large numbers. Therefore, public-key cryptosystems, or cryptographic algorithms, are extremely secure. One public-key cryptosystem is Rivest-Shamir-Adleman (RSA). It was created in 1977 by three people whose last names are those in the name of the cryptosystem. RSA usually uses a 1024- to 4096-bit key (or 128 to 512 bytes). Even today, RSA is used to securely exchange data. It was broken once, in 2009, when a 768-bit RSA key was factored by a computer. It took this computer two years to factor the key. (I will add more info here.)
Another common application of cryptography is chip-based credit cards.
Another commonly used implementation of cryptography is cryptocurrencies.