Key Terms 305 must be kept secure. Asymmetric cryptography can also be used to create a digital signature, which verifies the sender, proves the integrity of the message, and prevents the sender from disowning the message. Common asymmetric cryptographic algorithms include RSA, Diffie-Hellman, and elliptic curve cryptography. Cryptography can also be used to protect large numbers of files on a system or an entire disk. One of the most widely used asymmetric cryptography systems for files and e-mail messages on Windows systems is a commercial product called Pretty Good Privacy (PGP), while a similar program known as GNU Privacy Guard (GPG) is an open-source product. Microsoft's Encrypting File System (EFS) is a cryptography system for Windows operating systems that use the Windows NTFS file system. Cryptography can also be applied to entire disks, known as whole disk encryption. Whole disk encryption includes using products such as Microsoft Windows BitLocker and taking advantage of the Trusted Platform Module (TPM). Key Terms Advanced Encryption Standard (AES) A symmetric cipher that has been approved as a replacement for DES. algorithm Procedures based on a mathematical formula; used to encrypt the data. asymmetric cryptographic algorithm Encryption that uses two mathematically related keys. BitLocker A Microsoft Windows Vista hardware-enabled data encryption feature.