Advanced Encryption Standard (AES) Show Improve Article Save Article Like Article
Improve Article Save Article Advanced Encryption Standard (AES) is a specification for the encryption of electronic data established by the U.S National Institute of Standards and Technology (NIST) in 2001. AES is widely used today as it is a much stronger than DES and triple DES despite being harder to implement. Points to remember
That means it takes 128 bits as input and outputs 128 bits of encrypted cipher text as output. AES relies on substitution-permutation network principle which means it is performed using a series of linked operations which involves replacing and shuffling of the input data. Working of the cipher : The number of rounds depends on the key length as follows :
Creation of Round keys : Encryption : [ b0 | b4 | b8 | b12 | | b1 | b5 | b9 | b13 | | b2 | b6 | b10| b14 | | b3 | b7 | b11| b15 ] Each round comprises of 4 steps :
The last round doesn’t have the MixColumns round. The SubBytes does the substitution and ShiftRows and MixColumns performs the permutation in the algorithm. SubBytes : In this step each byte is substituted by another byte. Its performed using a lookup table also called the S-box. This substitution is done in a way that a byte is never substituted by itself and also not substituted by another byte which is a compliment of the current byte. The result of this step is a 16 byte (4 x 4 ) matrix like before. The next two steps implement the permutation. ShiftRows :
(A left circular shift is performed.) [ b0 | b1 | b2 | b3 ] [ b0 | b1 | b2 | b3 ] | b4 | b5 | b6 | b7 | -> | b5 | b6 | b7 | b4 | | b8 | b9 | b10 | b11 | | b10 | b11 | b8 | b9 | [ b12 | b13 | b14 | b15 ] [ b15 | b12 | b13 | b14 ] MixColumns : This step is skipped in the last round. [ c0 ] [ 2 3 1 1 ] [ b0 ] | c1 | = | 1 2 3 1 | | b1 | | c2 | | 1 1 2 3 | | b2 | [ c3 ] [ 3 1 1 2 ] [ b3 ] Add Round Keys : After all these rounds 128 bits of encrypted data is given back as output. This process is repeated until all the data to be encrypted undergoes this process. Decryption : The stages of each round in decryption is as follows :
The decryption process is the encryption process done in reverse so i will explain the steps with notable differences. Which are the operations in AES algorithm?DESCRIPTION OF AES ALGORITHM
The AES encryption process operates on four different operations such as Substitution byte, Shift row, Mix-column and Addround key. The decryption process also has four operations are Inverse substitution byte, Inverse shift row, Inverse Mix-column and Inverse add round key.
Which of the following are steps in each round of AES algorithm?For encryption, each round consists of the following four steps: 1) Substitute bytes, 2) Shift rows, 3) Mix columns, and 4) Add round key.
Which of the following operation is true for each round of AES algorithm?This is Expert Verified Answer
Substitution Bytes, Shift rows, Mix columns, Add round key.
Which of the following operations are not carried out for each round of AES?Explanation: In the AES algorithm, the MIX COLUMN operation is performed in all the rounds except the final round of the algorithm. 3) What does IDEA stand for in the world of cryptography?
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