Which encryption algorithm is commonly combined with the Poly1305 MAC algorithm for secure encryption?

The Poly1305 MAC algorithm is specifically designed to provide message authentication in conjunction with particular encryption schemes. One of the primary encryption algorithms that it is commonly paired with is ChaCha.

ChaCha is a stream cipher that was developed as a variant of the Salsa20 family to provide higher security and performance, particularly in constrained environments. When Poly1305 is used alongside ChaCha, it allows for authenticated encryption, which ensures data integrity and authenticity alongside confidentiality. This combination is particularly significant in various applications, including secure messaging and network protocols, due to its performance benefits and security assurances.

In contrast, while AES, GCM, and CBC are respected encryption methods, they are not typically combined with Poly1305. GCM, for example, has its own built-in MAC capabilities and is often used to provide authenticated encryption without the need for an additional MAC algorithm like Poly1305. Similarly, CBC is a mode of operation for block ciphers and does not directly pair with Poly1305 for its intended encryption purposes. Therefore, the link between Poly1305 and ChaCha highlights a specific and effective use case in cryptography for achieving robust security.