Historical Background of AES
The main concept for the advanced encryption standard was evolved in January 1997 by the NIST (National Institute of Standards & Technology. A robust replacement of the data encryption standard was required in the commerce department of United States unit to minimize the degree levels of the Data Encryption standard for this purpose symmetric algorithms were proposed because it was based on the structure with same encryption and decryption keys. The royalty free access of these algorithms was required which was not possible, so that finally symmetric algorithm called Cipher AES was introduced, which is of great use in terms of security.
Advancement in AES
After the arrival of AES, it was pin for public comment and feedback for improvement in the current standard. After one year of its advent NIST conducted open research and selected fifteen top candidates out of huge pool of research for the preliminary analysis for the further cryptography which involved sequence of processes from the National Security Agency. This process was the ground basis for the NIST to Select five algorithms for further analysis in 1999.some of those algorithms were MARS which was submitted by IBM research, RC6 by RSA security, Rijindael by two cryptographer based in the Belgium. The testing of all the above algos was extensively base don ANSI and java oriented languages, from which encryption and decryption speed as measured.
How Advanced Encryption Standard works
In AES the main architecture is centrally controlled both hardware and softwares. decryption of this system is dependent upon the designing rule which is called Substitution permutation networking .Advanced Encryption standard has standard blocks with fixed length of 128 bits and their allowed key size is 128,256 or it can be 256 bits, new research has evolved that multiple key size can be allocated to the block it could be 32 bits with the least capacity of 128 bits and its key size may be extended no fixed length is announced. its operations are based on the 4X4 matrix of the bytes with finite field calculations especially designed for the purpose of calculations. AES specifies the repetition numbers for converting the input to the normal readable text. An input provide by the user undergoes several steps of processing according to the encryption key provided. These steps are categorized as rounds and for converting the text back to the encrypted form same rounds are repeated with the same key which was used for decryption. Number of repetitions are decide on the nature and level of the algorithm used as the base of system .rounds are dependent on the schedule of the algorithm provide by the rijindael’s key
- In the initial round bitwise addition to the round key takes place. This is done by using XOR.
- Sub byte is another round in which every byte is finally replaced by another byte according to the table position and requirement. This process of substitution is non linear ,no fixed sequence is followed.
- Shifting of the rows is the next round in which every row is shifted backward or forward, up or down in a cyclic manner for specified number of times.
- Column mixing is another round where columns are mixed in which 4 bytes are joined together in one column.
Notes: Watch useful video for better undestand the concept of advanced encryption standards