A security administrator has been asked to implement a VPN that will support remote access over IPSEC. Which of the following is an encryption algorithm that would meet this requirement?

MD5 is a hashing algorithm used for integrity verification (authentication), not an encryption algorithm, so it cannot encrypt VPN traffic.

AES (Advanced Encryption Standard) is a symmetric block cipher and a valid encryption algorithm supported by IPSec for encrypting VPN tunnel traffic. It is used within IPSec's ESP (Encapsulating Security Payload) protocol to provide confidentiality, and is available in key sizes of 128, 192, and 256 bits, making it a strong and compliant choice for secure remote access VPNs.

UDP is a Layer 4 transport protocol used for transmitting data packets across networks, not an encryption algorithm; it has no encryption capability.

PKI (Public Key Infrastructure) is a framework for managing digital certificates and public-key encryption, not itself an encryption algorithm that can be directly applied to IPSec tunnel encryption.