Hash functions that compute a fixed-length message digest from arbitrary length messages are widely used for many purposes in information security. This document provides security guidelines for achieving the required or desired security strengths when using cryptographic applications that employ the approved hash functions specified in Federal Information Processing Standard (FIPS) 180-4. These include functions such as digital signatures, Keyed-hash Message Authentication Codes (HMACs) and Hash-based Key Derivation Functions (Hash-based KDFs).