2.7: Authenticated Encryption and Further Modes of Operation

What is Authenticated Encryption (AE)?

Combines Encryption and Data Origin Authentication to:

• encrypt the message

• authenticate the message

How is AE achieved?

1. Using block cipher for encryption and a separate MAC for authentication (Generic Composition)

2. Using integrated AE algorithms

Integrated AE Algorithms

Designed to allow safe use of a single symmetric key for both encryption and authentication

Identified by naming a block cipher and an AE family

What is Authenticated Encryption with Associated Data (AEAD)?

Used when:

• Message data needs to be encrypted

• Associated data should be authenticated but not encrypted

CCM Mode of Operation

an AEAD method combining:

• CTR (counter) mode for encryption

• CBC-MAC for authentication

Commonly used with the AES block cipher and provides both encryption and authentication for sensitive data and associated data

What are ChaCha20 and Poly1305 used for in Cryptography?

ChaCha20:

• a stream cipher designed for better performance in environments without AES hardware support, using 20 rounds of an underlying cipher ChaCha

Poly1305:

• MAC algorithm used for authentication

ChaCha20 and Poly1305 form an AEAD algorithm that is widely used for high security, efficient encryption and authentication