RFC 1321 defines which hashing algorithm?

RFC 1321 defines the MD5 hashing algorithm, which was developed by Ronald Rivest in 1991. MD5 is widely used in various applications and protocols for producing message digests, ensuring data integrity, and verifying data authenticity. Its design allows for the generation of a fixed-size 128-bit hash value from an arbitrary amount of input data, making it a popular choice for checksums.

Despite its widespread use, it's important to note that MD5 has vulnerabilities and is no longer considered secure against collision attacks. As a result, newer hashing algorithms such as SHA-1, SHA-256, and RIPEMD-160 have been developed and are recommended for cryptographic purposes. These newer algorithms offer better security and resilience against detection or manipulation, but RFC 1321 remains specifically tied to the MD5 algorithm.