Symmetric Encryption
Last updated
Last updated
In the encryption-based system, the transmitter and recipient utilize a single com- mon key to encrypt and decrypt the message.
Figure 1.1 shows the symmetric encryption mechanism. However, the public-key cryptography approach uses two keys for encryption and decryption purposes, public and private keys. Though the symmetric encryption method is faster, the main concern is security, and the keys should transfer their information in a very secure way. This encryption method is also known as secret-key cryptography. At the same time, public-key cryptography is not facing this issue because it has not transmitted their private key and easily distributes their public key.
In this following subsection, we will discuss various symmetric encryption algorithms.
A famous symmetric encryption algorithm that was developed in 1975 is Data Encryption Standard (DES) approach.
The block cipher method and 56-bit key DES split the text into 64-bit blocks and encrypt that text. Generally, the DES algorithm uses the same key for the encryption and decryp- tion so that the transmitter and recipient both use the same private key. Figure 1.2 shows the vital feature of the DES algorithm such as block cipher, numerous rounds of encryption, 64-bit key, backward compatibility, and replacement and permutation. DES uses the block cipher method to mean that the key and algorithm apply to an entire data block rather than one bit at a particular time. DES encrypts the text 16 rounds in four different modes. It can encrypt the block separately and make the cipher block depending on its previous block. The ciphertext describes the sequence of permutations and replacements during the encryption process. However, this algo- rithm has benefited that it is not secure enough against brute force attacks. So, DES is replaced by a more advanced algorithm, discussed in a subsequent topic.
A mode of the DES encryption approach, which is known as triple DES or 3DES, encrypts message three times. It has a key length of 192 bits and utilizes 64-bit keys. It utilizes the cartographic block method, in which the text is split into 64-bit size text blocks. Encryption is done after that. In triple DES, the first encryption key encrypts with the second encryption key. Likewise, the resultant ciphertext is encrypted using a third encryption key. That is the reason 3DES is more secure than the DES algorithm. The encryption and decryption process in 3DES are as follows:
Encryption: ct = E3(D2(E1(P)))
Decryption: P = D1(E H2(D3(ct)))
In the above-mentioned, E() represents encryption and D() shows the decryption of the DES approach. H, P, and ct denote key, plain text, and ciphertext.
United States government standard replaced the DES algorithm in 2002 with the Advanced Encryption Standard (AES) approach. Joan Daemen and Vincent Rijmen—Belgian cryptographers—evolved a symmet- ric 128-bit block message encryption approach. The AES algorithm can work simultaneously in multiple network environments. Initially, the National Institute of Standards and Technology (NIST) of the U.S. Department of Commerce has deter- mined the Rijndael approach from all the given five methods. This approach is similar to the AES algorithm. The only difference between Rijndael and AES is that Rijan- dael can define with any key and block size that are multiples of 32 bits such as a minimum of 128 bits and a maximum of 256 bits. In contrast, AES has a fixed block size (128-bit) and 128-bit, 192-bit, and 256-bit key size. This algorithm is secure enough against the brute force attack compared to the DES and 3DES
