About AES Encryption
The Advanced Encryption Standard (AES) is a symmetric block cipher chosen by the U.S.
government to protect classified information. It is implemented in software and hardware
throughout the world to encrypt sensitive data.
- AES is a symmetric key algorithm, meaning the same key is used for both encryption
and
decryption.
- It operates on fixed-size blocks of data (128 bits) using cryptographic keys of 128,
192, or 256 bits.
- AES is considered secure against all known practical attacks.
How AES Works:
- Key Expansion: The AES key is expanded into a key schedule.
- Initial Round: AddRoundKey - each byte of the state is combined with a block of the
round key using bitwise XOR.
- Rounds (9, 11, or 13 rounds depending on key size):
- SubBytes - a non-linear substitution step where each byte is replaced with
another according to a lookup table.
- ShiftRows - a transposition step where the last three rows of the state are
shifted cyclically.
- MixColumns - a mixing operation which operates on the columns of the state,
combining the four bytes in each column.
- AddRoundKey
- Final Round (without MixColumns):
- SubBytes
- ShiftRows
- AddRoundKey