# AES - Advanced Encryption Standard

Encryption at its BEST !

### AES

- Original Name - Rijndael
- Efficient Algorithm that supports both hardware & Software
- Supports a block length of 128 bits data and key lengths of 128, 192, and 256 bits.
- Supersedes DES – Data Encryption Standard
- Supports Symmetric key Encryption.
- Result of the encryption is base64 encoded to prevent character encoding problems.
- AES encryption is used by U.S. for securing sensitive but unclassified material, so we can say it is enough secure.
- Six time faster than triple DES.
- It replaced DES as key size was too small (key length of 64 bits, however 8 bits are used for parity, therefore the effective key length is 56 bits.
- based on ‘substitution–permutation network - series of linked operations, some of which involve replacing inputs by specific outputs (substitutions) and others involve shuffling bits around (permutations).
- Performs all its computations on bytes rather than bits. Hence, AES treats the 128 bits of a plaintext block as 16 bytes. These 16 bytes are arranged in four columns and four rows for processing as a matrix
- The number of rounds in AES is variable and depends on the length of the key. AES uses 10 rounds for 128-bit keys, 12 rounds for 192-bit keys and 14 rounds for 256-bit keys. Each of these rounds uses a different 128-bit round key, which is calculated from the original AES key
- four processes conducted – [Add round key -Mix columns -Shift rows -Byte substitution]
- Decryption – Reverse process –[ Byte substitution - Shift rows - Mix columns Add round key ]
- Built-in flexibility of key length, which allows a degree of ‘future-proofing’ against progress in the ability to perform exhaustive key searches.
#### What are AES – Modes

- Procedural rules for a generic block cipher. Different modes of operation of a block cipher.
- Different modes result in different properties being achieved which add to the security of the underlying block cipher.
- Modes are - ECB, CBC, CFB, OFB, CTR

Dimit Chadha SECURITY

security security Keys Encryption Decryption AES Symmetric Keys

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