The VPN Gateway must use FIPS-validated SHA-2 or higher hash function to protect the integrity of hash message authentication code (HMAC), Key Derivation Functions (KDFs), Random Bit Generation, hash-only applications, and digital signature verification.

Without cryptographic integrity protections, information can be altered by unauthorized users without detection. Although allowed by SP800-131Ar2 for some applications, SHA-1 is considered a compromised hashing standard and is being phased out of use by industry and Government standards. Unless required for legacy use, DoD systems should not be configured to use SHA-2 for integrity of remote access sessions.