Introduction to Advanced Encryption Standard (AES)

Summary

This presentation introduces the Advanced Encryption Standard (AES), a powerful and widely used symmetric block cipher published by NIST in 2001. It explains AES as an alternative to DES, highlighting its structure, parameters, and the relationship between key size and the number of encryption rounds. The video covers the AES process, which involves an initial transformation and multiple rounds of four transformations (Substitute Bytes, Shift Rows, Mix Columns, Add Round Key), culminating in the final ciphertext. AES is available in three key sizes: 128, 192, and 256 bits, each with a varying number of rounds, ensuring a balance between security and performance.

Takeaways

• 🔒 AES stands for Advanced Encryption Standard, a symmetric block cipher encryption algorithm.
• 📈 AES was published by the National Institute of Standards and Technology (NIST) in 2001, succeeding DES which is considered less secure.
• 🔑 AES operates on a fixed block size of 128 bits for both plaintext and ciphertext, unlike DES which used 64 bits.
• 🛠️ AES involves an initial transformation and multiple rounds of transformations, with the number of rounds varying based on key size.
• 🔑 The key size in AES can be 128, 192, or 256 bits, which influences the number of encryption rounds: 10, 12, or 14 rounds respectively.
• 🔄 AES has three variations: AES-128, AES-192, and AES-256, with each requiring a different key size and number of encryption rounds.
• 🗝️ Each round in AES, except the last, involves four types of transformations: Substitute Bytes, Shift Rows, Mix Columns, and Add Round Key.
• 🔄 The final round in AES has three transformations instead of four, simplifying the process for the last step of encryption.
• 🔑 The round keys for each transformation round are generated by a key scheduling algorithm from the original key provided.
• 📚 AES is widely used due to its powerful features and is considered a secure encryption standard in today's world.

Q & A

What does AES stand for?

AES stands for Advanced Encryption Standard, which is a symmetric block cipher used for encrypting and decrypting data.

Who published the AES standard?

The AES standard was published by the National Institute of Standards and Technology (NIST) in the year 2001.

What is the block size of AES?

The block size of AES is 128 bits, which means it processes data in blocks of 128 bits at a time.

What is the purpose of the state array in AES?

The state array in AES is a 16-byte (128 bits) structure that stores the plaintext or ciphertext during the encryption and decryption processes.

How many rounds does AES typically go through during the encryption process?

The number of rounds in AES depends on the key size: 10 rounds for a 128-bit key, 12 rounds for a 192-bit key, and 14 rounds for a 256-bit key.

What are the four transformations applied in each round of AES, except the last round?

The four transformations applied in each round of AES, except the last round, are Substitute Bytes, Shift Rows, Mix Columns, and Add Round Key.

What is the difference between the transformations in the last round of AES and the other rounds?

In the last round of AES, only three transformations are applied instead of four. The Mix Columns transformation is omitted in the final round.

What is the relationship between the key size and the number of rounds in AES?

The key size determines the number of rounds in AES: a 128-bit key results in 10 rounds, a 192-bit key results in 12 rounds, and a 256-bit key results in 14 rounds.

What is the size of the round keys used in AES?

The size of the round keys used in AES is always 128 bits, regardless of the original key size.

How does AES differ from DES in terms of security and key size?

AES is considered more secure than DES and offers variable key sizes of 128, 192, or 256 bits, compared to DES which uses a 56-bit effective key size.

What is the significance of the initial transformation in AES?

The initial transformation in AES is the first step in the encryption process where the input state array is transformed using the round 0 key before proceeding to the rounds.