Which authenticated encryption mode is designed to provide strong message authentication and is fast?

The answer is rooted in the characteristics and efficiencies of Poly1305 as an authenticated encryption mode. Poly1305 is designed specifically to provide strong message authentication at high speeds. It calculates a message authentication code (MAC) that ensures the integrity and authenticity of the message, which is essential for secure communications.

The design of Poly1305 allows it to operate in a high-performance manner, making it particularly well-suited for systems that require both security and efficiency. Its performance is further enhanced when used in conjunction with stream ciphers or block ciphers operating in certain modes, like CTR mode, enabling the establishment of authenticated encryption schemes.

In contrast, other modes like Cipher Block Chaining (CBC) and Electronic Codebook (ECB) primarily focus on encryption rather than combined authentication, which makes them less suitable for scenarios requiring robust message integrity checks. Meanwhile, the Counter (CTR) mode, while fast and allowing for parallel processing, does not inherently provide authentication, necessitating an additional mechanism for message integrity.

By prioritizing both speed and strong authentication, Poly1305 stands out as a compelling option in situations where efficiency and security are paramount.