Fundamentals of Cryptography: Techniques and Algorithms


Fundamentals of Cryptography: Techniques and Algorithms in Computer Science

Cryptography, the science of secret communication, has been used for centuries to protect sensitive information from falling into the wrong hands. With the ever-growing threat of cyber attacks and the need for secure communication in the digital age, cryptography has become an essential tool in computer science. In this article, we will delve into the fundamentals of cryptography, exploring its techniques and algorithms and providing practical examples that showcase its importance in computer science.

Techniques of Cryptography:

The two fundamental techniques of cryptography are encryption and decryption. Encryption involves converting plain, readable text into a non-readable format, also known as ciphertext, using a mathematical algorithm and a secret key. Decryption, on the other hand, is the process of converting the ciphertext back into its original form using the same key.

Symmetric Key Cryptography:

Symmetric key cryptography, also known as shared key cryptography, is a technique where a single key is used to encrypt and decrypt information. This key must be kept secret between the sender and receiver to ensure the security of the communication. One of the most widely used algorithms in symmetric key cryptography is the Advanced Encryption Standard (AES) that uses a 128-bit block size and key length of 128, 192, or 256 bits.

Asymmetric Key Cryptography:

Asymmetric key cryptography, also known as public key cryptography, involves the use of two different keys – a public key and a private key. The sender uses the public key to encrypt the message, which can be accessed by anyone, while the receiver uses the private key to decrypt the message, which remains confidential. The most commonly used algorithm in asymmetric key cryptography is the Rivest–Shamir–Adleman (RSA) that uses large prime numbers and is based on the mathematical difficulty of factoring large numbers.

Hash Functions:

Hash functions are essential in cryptography to ensure the integrity of the message. A hash function is a mathematical algorithm that takes a variable-length input and produces a fixed-length output, known as a hash value. The most used hash function is the Secure Hash Algorithm (SHA), which generates a 160-bit or 256-bit hash value.

Practical Examples:

One of the most widely used practical examples of cryptography is in online transactions and e-commerce. When you make a purchase online, your credit card information is encrypted using symmetric key cryptography, and only the receiver can decrypt it using the shared key. This ensures the protection of your sensitive information from hackers and cybercriminals.

Another example is the use of asymmetric key cryptography in secure email communication. Suppose you want to send an email containing sensitive information to a colleague. In that case, you can encrypt the message using their public key, and only they will be able to decrypt it using their private key. This way, the message remains confidential and secure from any potential eavesdroppers.


In conclusion, the fundamentals of cryptography are essential in computer science as they provide secure communication, data protection, and integrity of information. With the advancement of technology and the increasing threat of cyber attacks, it is vital to have a strong understanding of cryptography techniques and algorithms. From online transactions to secure email communication, cryptography plays a crucial role in safeguarding sensitive information in the digital world. As technology continues to evolve, so will the techniques and algorithms of cryptography, making it an ever-important aspect of computer science.