Cryptography - Classical vs Quantum



As we know, cryptography consists of two processes: encryption and decryption, which operate at the sender and receiver ends, respectively. Basically, cryptography is the practice or implementation of secure communication between sender and receiver in a public environment in such a way that no one other than these two parties can receive or interpret the message that is delivered.

So in this chapter we will examine what is classical and quantum Cryptography and also what are the differences between these two types of Cryptographies.

What is Classical Cryptography?

Throughout the ages, people have used classical cryptography to keep data secure using codes and ciphers as well. Before the advent of computers, people have been using this for a considerable amount of time. Classical cryptosystems use processes on substitution based codes, which substitute one letter from the plaintext for another letter from the ciphertext alphabet in order to transform clear texts into unknown ones; transposition techniques, where every character found in text either remains stationary or moves with respect to other characters according strict relationship are observed. Caesar cipher plus Vigenere cipher are some typical examples. This is known as traditional encryption because it is what we used to do long time ago.

The basis of modern cryptographic techniques was set down by traditional cryptography and in addition to this, a number of its methods have been made vulnerable to the advanced attacks as well computational power which exist today. It is because this reason why today's sophisticated cryptographic schemes make use of difficult mathematical algorithms together with computational procedures in their encryption as well as decryption processes.

What is Quantum Cryptography?

A cutting-edge field in the Quantum revolutions is the quantum cryptography that relies on quantum physics in order to secure communication channels, in contradistinction with classical cryptography that appeals to mathematical methods.

Here are some key aspects of quantum cryptography −

  • There typically is a link between quantum cryptography and QKD. In particular, the latter is a mechanism for transmitting cryptographic keys securely between two parties. It owes its security to domesticated quantum properties like superposition and entanglement that help create an uncrackable by any third party shared secret key. The point is that when eavesdropping on quantum communication is undertaken, this inevitably leads to a destruction of quntum state which in turn alerts participants of a potential intruder.
  • Quantum cryptography makes use of fundamental quantum physics concepts like the principle of uncertainty and the no-cloning theorem. These principles provide foundations for secure key distribution and detection of eavesdropping attempts.
  • Unlike traditional cryptographic systems, which depend on the computational difficulties of specific mathematical problems, quantum cryptography offers security guarantees using physical constants. As a result, it is believed to give unconditional protection against some types of attacks, like those based on processing capacity.
  • Several protocols have been created to implement QKD, including BB84, E91, and SARG04. These protocols describe how to send quantum information and create secure keys between parties.

Difference between Classical and Quantum Cryptography

Here is a simple table of comparison between classical and quantum cryptography −

Aspect Classical Cryptography Quantum Cryptography
Basis Relies on mathematical algorithms and computational complexity. Utilizes principles of quantum mechanics.
Security Basis Security often relies on computational complexity and mathematical hardness. Security is based on fundamental principles of physics.
Key Distribution Typically uses public key or symmetric key algorithms for key distribution. Utilizes quantum key distribution (QKD) protocols for secure key exchange.
Security Guarantees Security guarantees are based on computational complexity assumptions. Offers unconditional security based on the laws of physics.
Eavesdropping Detection Detection mechanisms are often based on mathematical analysis and algorithms. Eavesdropping detection relies on the principles of quantum mechanics, such as disturbance of quantum states.
Vulnerabilities Vulnerable to attacks based on computational power, such as brute-force attacks. Offers resistance to attacks based on computational power due to its reliance on quantum principles.
Implementation Implemented using classical computers and algorithms. Requires specialized quantum hardware for implementations.
Practicality Widely used and implemented in various applications. Still in the research and development stage, with limited practical implementations.
Key Management Requires careful management of keys and regular updates to maintain security. Offers potential for more secure key management due to the unique properties of quantum states.

Summary

To summarise, classical and quantum cryptography are two methods for securing secure communication between parties. Classical encryption uses algorithms and computer complexity, but quantum cryptography uses quantum physics principles to assure secure communication.

Classical cryptography is widely used in a number of applications, but quantum cryptography is still in the research and development stage, with few practical implementations. Classical encryption needs careful key management, whereas quantum cryptography provides the potential for better key management due to the unique features of quantum states.

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