Review on Symmetric and Asymmetric Cryptography

Abstract

As the technology is progressing, internet is growing day by day and it has became more vulnerable than ever. To prevent data from being tampered or viewed by third parties, cryptography is used. Cryptography has it’s roots from ancient egypt, where secret writings are developed to transfer messages. Now, modern cryptography is used to secure data over the network, which are classified into symmetric and asymmetric cryptography. Both cryptographic methods has it’s own lim- itations and advantages, which are further used to develop algorithms for better security. More and more efficient algorithms are developed which are discussed in this paper.

Introduction

I. INTRODUCTION

Cryptography is defined as the study and practice of tech- niques used to hide information. It dates all the way back to ancient Egypt but still in use to prevent information from undetected alteration or being read by unauthorized person. The term cryptography is derived from Greek words “krypto´s” and “gra´phein” which can be interpreted as “hidden writing”. In a broad sense cryptography is a process to secure commu- nications and information in transit. As shown in the diagram below message is encrypted using a key and an encryption algorithm, then transferred over an unsecure network to the receiver and is decrypted using the same algorithm and de- cryption key to obtain the original message. [1]

For the process of encryption and decryption an algorithm is used described as cryptographic algorithm. An algorithm is comprised of mathematical functions used to transform plain-text into cipher-text. Cryptographic algorithms are being evolved as the time progress and with the advancement in the technology.

Some of the earlier ciphers that are Caeser cipher, Vignere cipher which were compromised due to technological advance- ments. During the time of world war Enigma cipher was adopted by Germans to secure their communications, which was eventually broken by British intelligence, compromising the geographical coordinates for attacks. In the modern era various algorithms were developed such as Advanced En- cryption Algorithm, Data Encryption Standard, Blowfish, RC4 which are based on advanced transposition and substitution techniques. A new approach for encryption and decryption of methods is developed which involves use of complex mathematical functions, which is considered as the most secure form of cryptographic algorithms till date. Some of them are Rivest Shamir Adleman, Diffie Hellman, Elliptical Curve Cryptography. [3] Cryptographic algorithms are defined on the basis of four basic principles which can be described as follows:

A. Confidentiality

This is the primary aspect of cryptogra- phy, used to keep information in secure and private manner. Suppose sender A sends the message to receiver B, but it is intercepted in the channel confidentiality makes sure that data is not compromised. This is extremely important in financial, government sectors. As there are million of transactions happening on day-to-day basis and classified documents are being shared over the network. Data confidentiality ensures that information stays hidden to the third party.

B. Data Integrity

Integrity of data ensures that data trans- ferred over the network has not been tampered or altered by an eavesdropper. There is no way of knowing that data has been modified or completely changed on the network. A common example is transfer of emails over the network. They doesn’t offer any security and which makes it very easy to alter or completely change the message that is being transmitted. To avoid such type of intrusions hash digest are used, these are used to generate message digests which are sent along with the original message and both are compared at the receiver’s end to ensure integrity of data.

C. Authentication

It makes sure that information is received by the only person to whom it belongs. Suppose sender A sends the message to user B, and the message is read by the B by performing the operations that can only be performed by user B, ensures that message is authenticated.

D. Non Repudiation

It ensures that sender of the message is the one who say it is. An example would be if sender A sends the message to user B and denies sending it, to prevent it from happening digital signatures, message authentication codes are used. [4]

Cryptography is classified into two categories symmetric cryptography and asymmetric cryptography which is further discussed in the following sections.

II. SYMMETRIC KEY CRYPTOGRAPHY

Symmetric cryptography is used for encryption of the message, in which sender and receiver shares the similar key to maintain the confidentiality of the message. Symmetric key ciphers are divided into two types, stream cipher and block cipher. Stream cipher takes input as the individual characters whereas block cipher converts whole block of text. To better understand symmetric cryptography lets take an example where M is the plain-text, C is the cipher-text, K is the Key and (E, D) refers to the pair of encryption and decryption.

• E : X x K → C; plain-text along with the key is used to produce the cipher-text.
• D : C x K → M; cipher-text along with the key is used to produce plain-text.

Symmetric ciphers are evolved according to the needs and advancement in technology, which can be furthur discussed below:

A. Caeser Cipher

Caeser cipher is one of the oldest way to transfer messages securely, which was used in ancient times. This cipher is based on the shifting of alphabets a certain number of times. A caeser cipher with an offset of 2 will shift the original letter with letter placed after two places. An example would be message ’A’ would be converted to ’D’. This cipher was used in ancient times and was named after King Julius Caeser. It’s major drawback lies in it’s security, it can be easily broken by brute force attack. [4]

Conclusion

In this paper a brief discussion of different symmetric and asymmetric key algorithms is provided. Symmetric key algo- rithms are based on combination of substitution and permuta- tion methods, which makes them very efficient as compared to asymmetric key algorithms. Symmetric key algorithms are less secure as they don’t use complex and unsolvable methods to perform encryption and decryption. Asymmetric key algorithms uses more complex mathematical functions and they require heavy calculations makes them less efficient but more secure. In the modern times a blend of both algorithms are used to develop secure protocols making them both secure and efficient at the same time.

References

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Copyright

Copyright © 2024 Bhanu Sankhyan, Anupam Baliyan, Abhishek Kumar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.