Block Cipher
What is Block Cipher?
Block CipherA symmetric cipher that encrypts fixed-size blocks of plaintext with a secret key, usually combined with a mode of operation to handle data of arbitrary length.
A block cipher is a deterministic, keyed permutation that maps fixed-size plaintext blocks to ciphertext blocks of the same size — for example 64 bits in DES and 128 bits in AES. Internally it iterates a round function (Feistel, substitution-permutation, or Lai–Massey) several times under a key schedule derived from the secret key. To encrypt messages longer than one block, a block cipher is wrapped in a mode of operation: ECB (insecure, deterministic), CBC, CTR, XTS for disk encryption, and authenticated modes such as GCM, CCM, or GCM-SIV that also provide integrity. Choice of mode, correct IV/nonce handling, and the block size all affect security; modern systems should use 128-bit-block ciphers (AES) in authenticated modes.
● Examples
- 01
AES is a 128-bit-block cipher used in modes like GCM, CBC, and XTS.
- 02
DES is a 64-bit-block cipher, now obsolete due to its small key size.
● Frequently asked questions
What is Block Cipher?
A symmetric cipher that encrypts fixed-size blocks of plaintext with a secret key, usually combined with a mode of operation to handle data of arbitrary length. It belongs to the Cryptography category of cybersecurity.
What does Block Cipher mean?
A symmetric cipher that encrypts fixed-size blocks of plaintext with a secret key, usually combined with a mode of operation to handle data of arbitrary length.
How do you defend against Block Cipher?
Defences for Block Cipher typically combine technical controls and operational practices, as detailed in the full definition above.