Which of the following are recognized examples of hash functions?

MD5 and SHA1 are both well-known cryptographic hash functions utilized for various purposes, such as ensuring data integrity and generating checksums. A hash function takes input data and produces a fixed-size string of characters, which appears random. The primary attributes of a good hash function include being deterministic (the same input always produces the same output), quick to compute, and collision-resistant (it should be challenging to find two different inputs that produce the same hash output).

MD5, which produces a 128-bit hash value, was widely used but has vulnerabilities that can lead to collisions, making it less secure over time. SHA1, producing a 160-bit hash value, also has known weaknesses and is no longer considered safe for cryptographic purposes. However, both examples are still recognized hash functions, highlighting their significance in the history of cryptography.

In contrast, the other options include algorithms and methods that perform different functions. DSA (Digital Signature Algorithm) and RSA (Rivest-Shamir-Adleman) are both asymmetric encryption algorithms, while HMAC (Hash-based Message Authentication Code) is a construction for creating a message authentication code using a hash function and a secret key. CBC (Cipher Block Chaining) is a mode of operation