Which are examples of hash functions?

• A. MD5 and SHA1
• B. RSA and SHA1
• C. AES and MD5
• D. HMAC and MD5

Answer: (A)

Hash functions take input of any length and produce a fixed-size digest, intended to be deterministic and one-way for integrity checks. MD5 and SHA-1 are classic examples of this kind of function: MD5 yields a 128-bit digest, and SHA-1 yields a 160-bit digest. They’re used to create a compact representation of data to verify that content hasn’t been altered.

The other items aren’t hash functions. RSA is an asymmetric encryption algorithm, used for encrypting data or creating digital signatures; AES is a symmetric encryption algorithm, used for encrypting data with a shared secret key; HMAC is a keyed authentication code built from a hash function, not a hash function by itself. Therefore, MD5 and SHA-1 are the correct examples of hash functions.