Provide (2) 150 words response with a minimum of 2 APA references at the discussions below. Response provided should further discuss the subject or provide more insight.
Data Encryption Standard (DES): This used to be a the standard encryption system between 1970 and 2001 using the Feistel Block Cipher(TutorialPoint 2019). The way that it works is through a process 16 repeated processes of key creation, expansion and scrambling. The initial phase has a static scramble of the first 8 bits that will be inverted back at the final of the permutation. However, everything else will be scrambled with a 48 bit key that is generated out of 64 bit key. This generated key will be paired and scrambled with the right most 32 bits of the actual information that needs to be encrypted. This process can only happen after the 32 bits are expanded to 48 so it can be placed in the substitution box (S-BOX) where the actual scrambling happens. The output of this S-Box is a 32 bit block that will go through this process 16 more times. a new 48 round key will be generated, the 32 bit block will be expanded to a 48 bit piece, and then passed through the S-BOX. This seemed pretty robust encryption method until 1999 where the cipher was decoded in less than 24 hours! (Lake 2018)
Advanced Encryption Standard (AES) follows similar process but plays with higher number of bits and the number of rounds of scramble is dependent of the cypher key length. The increased key lengths of 128, 192, and 256 bits makes brute force attacks virtually impossible. Additionally the S-Box uses a different shifting mechanism by using RIJNDAEL cipher by using byte arrays and shifting their position and transforming the data using polynomial matrix multiplication (RIJNDAEL 2000). After a couple of rounds of this the encryption is accomplished and has proven to be effective for the time being(Lake 2018).
Tutorial Point. 2019. Data Encryption Standard. Retrieved from https://www.tutorialspoint.com/cryptography/data_encryption_standard.htm
Lake, J. 5 Oct, 2018. What is AES Encryption and how does it work? Retrieved from https://www.comparitech.com/blog/information-security/what-is-aes-encryption/
RIJNDAEL. 15 Nov, 2000. Retrieved from https://www.cs.mcgill.ca/~kaleigh/computers/crypto_rijndael.html
DES and AES are both symmetrical block ciphers. DES is not considered as secure as AES because of the smaller key size. One of the main differences between the two is when the cipher is generated. In DES the data block is divided into two 32 bit halves. Then the halves are used to create the key and cipher. In AES the data block is not separated to complete this process. This process is known as the s-box.
Another major difference is the p-box or permutation. In AES, once the entire data block has gone through the S-box, it goes through 10 rounds of permutations for 128 bit, 12 rounds for 192 bit, and 14 rounds for 256 bit. In DES once that data block is split, each half goes through 16 rounds of permutation.
Key size is also a major difference between AES and DES. As stated in the previous paragraphs, the key size for DES is 64 bit. There are a few different key sizes available for AES: 125 bit, 192 bit and 256 bit.