A company is planning to encrypt the files in several sensitive directories of a file server with a symmetric key. Which of the following could be used?

RSA is an asymmetric encryption algorithm that uses a public/private key pair, making it computationally expensive and impractical for encrypting large amounts of file data directly.

Twofish is a symmetric block cipher that uses a single shared key for both encryption and decryption, making it ideal for encrypting files at rest. It supports key sizes up to 256 bits and was one of the five finalists in the AES competition, making it a well-vetted and secure choice for bulk data encryption such as files in sensitive directories.

Diffie-Hellman is a key exchange protocol used to securely establish a shared secret over an insecure channel, not an encryption algorithm used to encrypt data.

NTLMv2 is a challenge-response authentication protocol used for Windows network authentication, not an encryption algorithm for encrypting files.

RIPEMD is a cryptographic hash function used to produce a fixed-length digest for integrity verification, not a symmetric encryption algorithm capable of encrypting and decrypting data.