The study and application of secure communication methods in the presence of third parties is known as cryptography. It can also be used to establish a safe connection among two systems. Under particular conditions, cryptography uses mathematics-mostly arithmetic and number theory-to guarantee the confidentiality, integrity, and authenticity of messages. By making sure that data cannot be read or modified while data is being transit, where unauthorised people can hack and read, it protects confidentiality.

The first thing to understand about cryptography is that there is no one way to universally encrypt a message. There are multiple methods and each has benefits and drawbacks. Public and symmetric key cryptography are currently the most widely used encryption techniques.

Many cryptographic algorithms are simply derived from other applications, like encryption methods for secure transactions across unreliable networks like the Internet or digital signature schemes. For example, factorising integers was the original purpose of the development of RSA cryptosystems.

Criminals regularly use cryptography to avoid identifying and transmit illegal messages without being detected. Public-key cryptosystems, like RSA, which are widely used in security protocols, also use it.

Types of Cryptography

The majority of encryption techniques can be divided into three categories: symmetric cryptography algorithms, and asymmetric cryptography algorithms, and hash functions while hybrid systems like the SSL internet protocols do exist. Let us see the types of cryptography in the section below.

• Symmetric Key Cryptography

• Asymmetric Key Cryptography

• Hash Functions

Symmetric Key Cryptography

Symmetric key encryption, commonly referred to as private key cryptography, secret key cryptography, or single key encryption, uses a single key for both the encryption and decryption processes. Every user needs to have access to the same private key in these kinds of systems. Private keys can be exchanged using a Diffie-Hellman key agreement or, more accurately, through a secure key exchange technique like a previously established secure communication channel such as a private courier or secured line.

So we can use the same key to lock and unlock messages. It is like having a secret code that you and your friend both know. It is very simple and fast. The two parties share the key in a secure way.

Two categories of symmetric key algorithms exist −

• Block Cipher − The cipher algorithm operates on a fixed-size block of data in a block cpher. As an example, eight bytes of plaintext are encrypted at a time if the block size is eight. When handling data larger than the block size, the user interface for the encrypt/decrypt process typically calls multiple times the low-level cipher function.

• Stream Cipher − Stream ciphers transform data one bit (or one byte) at a time instead of operating on a block basis. Simply say, a stream cipher uses a given key to generate a keystream. The plaintext data is then XORed with the generated keystream.

Examples of Symmetric Cryptography are as follows: DES, Triple DES, Blowfish, AES.

Asymmetric Key Cryptography

Unlike symmetric encryption cryptography, we use two keys in this type of cryptography: one for encryption and second one for decryption. Since these keys can be reused several times and are only used once per message, they do not need to be kept secret. Public-key systems are the most common use case for asymmetric key cryptography.

Two keys are utilised in asymmetric encryption: a secret key and a public key. Because of this, another name for these algorithms is public key algorithms (PKA). Since only the intended recipient”s private key can be used to decipher an encrypted message, public key cryptography is typically thought to be more secure than symmetric encryption methods, even though one key is made available to the public.

Asymmetric key cryptography has many examples, like the following −

• Rivest, Shamier, and Adleman (RSA) − One of the first widely used public key cryptosystems for secure data transmission, the RSA algorithm was founded in 1977 and is named for its authors, Rivest, Shamier, and Adleman.

• Elliptic curve cryptography (ECC) − It is a modern type of asymmetric encryption that generates very strong cryptographic keys using the algebraic structures of elliptic curves.

Hash Functions

A hash function is like a special mathematical function which takes an input of arbitrary data like text, numbers, or files and converts it into a fixed-length string called a hash. We can say it is like a fingerprint for your data. Hash function can process any size of data but always gives output of fixed length value. The output is much smaller than the input.

Suppose you own a library that has millions of volumes. You are not going through each book”s page by page in the hope to quickly find a specific book. An index will be used instead, connecting unique page numbers (hashes) to book titles (data). Hash functions behave similarly for storing and retrieving data.

The following claims about a decent hash function are accurate for all purposes and reasons −

• Collision-resistant − Data integrity is maintained by generating a new hash whenever any part of the data is changed.

• One-way − This function cannot be undone. To ensure data security, a digest needs to make it impossible to locate the original data.

Because hash algorithms encrypt data directly without requiring separate keys, they are an extremely effective part of cryptosystems. In fact, the plaintext works as its own key.

Future Cryptography

• Quantum cryptography

• Post-quantum cryptography

Quantum cryptography

The field of cryptography keeps developing to keep up with the speed at which technology is developing and the high level of cyberattacks that are happening. The applied science of efficiently encrypting and transferring data based on the naturally occurring and permanent laws of quantum physics for application in cybersecurity is known as quantum cryptography, or quantum encryption. Quantum encryption is still in its early stages, but it has the potential to be significantly more secure than earlier cryptographic algorithm types and possibly even unhackable.

Post-quantum cryptography

Post-quantum cryptographic algorithms use various forms of mathematical cryptography to build quantum computer-proof encryption, which is not to be confused with quantum cryptography, which depends on the rules of nature to create secure cryptosystems. Quantum computing is a rapidly emerging topic in computer science that has the potential to significantly enhance processing power, potentially exceeding even the fastest super computers already in use, even though it is not yet practical. Although the most robust public key cryptography systems could be broken by practical quantum computers in the next 10 to 50 years, according to prototypes, even though these systems are currently theoretical.

Summary

Nowadays, the majority of information is accessible digitally. Computer systems are currently used to digitally record, analyse, and communicate important information. Due to the importance of information, hackers target computers in an attempt to obtain unauthorised access. This is the application of cryptography. A scalable collection of methods provided by cryptography ensures that the malicious aim of a hacker fails while allowing authorised users to access data.

We have seen numerous types of cryptography in this chapter, as well as cryptography in the future. Digital communications become more secure by cryptography, which transforms data into secret codes that are only decipherable by those with permission. By understanding these types of cryptography, we can protect sensitive information and we can do secure communication in our apps.