Lecture Notes: Advanced Encryption Standard (AES) What is AES? The Advanced Encryption Standard (AES) is a symmetric-key block cipher that has become the de facto standard for encryption in many applications. It was selected through a rigorous competition and is considered to be highly secure. Key Features of AES ● Block Size: AES operates on 128-bit blocks of data. ● Key Length: AES supports three key lengths: 128, 192, and 256 bits. ● Number of Rounds: The number of rounds varies depending on the key length: 10 rounds for 128-bit keys, 12 rounds for 192-bit keys, and 14 rounds for 256-bit keys. ● Rijndael Algorithm: AES is based on the Rijndael algorithm, which was one of the finalists in the AES competition. How AES Works 1. Initial Round: The plaintext block is subjected to an initial round transformation, which involves adding a round key and performing a substitution and permutation operation. 2. Rounds: The plaintext block is then processed through multiple rounds of encryption. Each round involves the following steps: ○ AddRoundKey: The round key is added to the block. ○ SubBytes: Each byte of the block is replaced with a new byte using a substitution table. ○ ShiftRows: The rows of the block are shifted cyclically. ○ MixColumns: The columns of the block are mixed using a matrix multiplication operation. 3. Final Round: The final round is similar to the previous rounds, but it omits the MixColumns step. 4. Output: The final result is the ciphertext. Advantages of AES ● Strong Security: AES is considered to be a highly secure algorithm, resistant to various types of attacks. ● Efficiency: AES is efficient to implement in both hardware and software. ● Widely Supported: AES is supported by a wide range of software and hardware platforms. Applications of AES ● Data Encryption: AES is used to encrypt sensitive data, such as credit card numbers, passwords, and medical records. ● Secure Communication: AES is used to secure communication channels, such as VPNs and HTTPS. ● Digital Signatures: AES can be used to generate digital signatures for verifying the authenticity and integrity of data. Conclusion AES is a powerful and versatile encryption algorithm that has become the de facto standard for many applications. Its strength, efficiency, and widespread support make it a popular choice for protecting sensitive data.