The F5 BIG-IP appliance IPsec VPN Gateway must use AES256 or higher encryption for the Internet Key Exchange (IKE) proposal to protect confidentiality of remote access sessions.

Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganization-controlled network. AES is the FIPS-validated cipher block cryptographic algorithm approved for use in DOD. For an algorithm implementation to be listed on a FIPS 140-2/140-3 cryptographic module validation certificate as an approved security function, the algorithm implementation must meet all the requirements of FIPS 140-2/140-3 and must successfully complete the cryptographic algorithm validation process. Currently, NIST has approved the following confidentiality modes to be used with approved block ciphers in a series of special publications: ECB, CBC, OFB, CFB, CTR, XTS-AES, FF1, FF3, CCM, GCM, KW, KWP, and TKW.

From the BIG-IP GUI: 1. Network. 2. IPsec. 3. IKE Peers. 4. Click on the Name of the IKE peer. 5. Verify an AES256 encryption algorithm is selected under IKE Phase 1 Algorithms >> Encryption Algorithm. If the BIG-IP appliance is not configured to use AES256 or greater encryption for the IKE proposal, this is a finding.

From the BIG-IP GUI: 1. Network. 2. IPsec. 3. IKE Peers. 4. Click on the Name of the IKE peer. 5. Configure an AES256 encryption algorithm under IKE Phase 1 Algorithms >> Encryption Algorithm. 6. Click "Update".