Encrypting File System
The Encrypting File System (EFS) introduced strong file system-level encryption to Windows. It allows any folder or drive on an NTFS volume to be encrypted transparently by the user. EFS works together with the EFS service, Microsoft's CryptoAPI and the EFS File System Runtime Library (FSRTL). To date, its encryption has not been compromised.
EFS works by encrypting a file with a bulk symmetric key (also known as the File Encryption Key, or FEK), which is used because it takes less time to encrypt and decrypt large amounts of data than if an asymmetric key cipher were used. The symmetric key used to encrypt the file is then encrypted with a public key associated with the user who encrypted the file, and this encrypted data is stored in the header of the encrypted file. To decrypt the file, the file system uses the private key of the user to decrypt the symmetric key stored in the file header. It then uses the symmetric key to decrypt the file. Because this is done at the file system level, it is transparent to the user.
For a user losing access to their key, support for recovery agents that can decrypt files is built into EFS. A Recovery Agent is a user who is authorized by a public key recovery certificate to decrypt files belonging to other users using a special private key. By default, local administrators are recovery agents however they can be customized using Group Policy..
Other articles related to "encrypting file system, files, system":
... encryption algorithms, depending on the version of Windows in use when the files are encrypted Operating system Default algorithm Other algorithms Windows 2000 DESX (none) Windows XP RTM ...
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