CBC
acronymcryptography
Stands for: Cipher Block Chaining
An older block-cipher mode that chains blocks together but provides no integrity on its own.
Cipher Block Chaining (NIST SP 800-38A) XORs each plaintext block with the previous ciphertext block before encrypting. It needs a separate MAC for integrity, and the order of those operations produced the BEAST, Lucky13, and POODLE attacks. TLS 1.3 drops CBC entirely.
Cipher block chaining XORs each plaintext block with the previous ciphertext block before encrypting, so identical blocks produce different output and the structure ECB leaks is hidden. It needs an unpredictable initialization vector for the first block.
Its defining weakness is that it provides no integrity. Without a separate authentication step an attacker can modify ciphertext and the recipient decrypts garbage without knowing it was tampered with, which is the basis of padding oracle attacks. That is why modern practice is AEAD rather than CBC plus a bolted-on MAC, and why TLS 1.3 removed CBC entirely rather than continuing to specify how to use it carefully.
Also known as: cbc