Mode of Operation

cryptography

Definition

Mode of Operation

A mode of operation is an algorithm that determines how to use a block cipher to process messages larger than a block.

Types

Classic Modes

Classic modes focus exclusively on data confidentiality. Additional mechanisms are required for integrity and authenticity (e.g. MACs). Examples include ECB, CBC, CFB, OFB, and CTR.

Authenticated Modes

Authenticated modes provide confidentiality, integrity, and authenticity simultaneously. Examples include GCM, CCM, and EAX.

Relevant Characteristics

Parallelisation

Possibility to parallelise encryption or decryption of message blocks.

Random Read Access

Possibility to access the content of a specific block without decrypting all preceding blocks.

Error Propagation

Impact of a change in the ciphertext on the decrypted plaintext. This is only relevant for classic modes; authenticated modes should abort decryption in case of integrity violations.