Now a temporary file Efs0.tmp is created in the same folder as the file being encrypted.
![efs file decryption tool efs file decryption tool](https://static3.avast.com/20180209/web/i/ransomware-decryption-tools/cryptomix-message-004.png)
Efs file decryption tool windows#
Please note, that on Windows XP not included into domain, there's no recovery agent is defined, so this step is omitted. If recovery agent is defined by system policy, EFS creates also Data Recovery Field (DRF) and places there FEK encrypted with public key of recover agent.Ī separate DRA is created for every recovery agent defined. Then, EFS creates Data Decryption Field (DDF) for the current user, where it places FEK and encrypts it with public key. EFS uses 1024-bit RSA algorithm to encrypt FEK. The next step is to get public/private key pair if it does not exist at this stage (the case when EFS invoked first time), EFS generate a new pair. Having the crypto context open, EFS generate File Encryption Key (FEK). It uses Microsoft Base Cryptographic Provider 1.0 as cryptographic provider. Then EFS aquires access CryptoAPI context. Symmetric algorithms are about 1000 times faster making their suitable for encrypting of large amounts of data.Īs a first setp to encrypt file, NTFS creates a log file called Efs0.log in System Volume Information folder on the same drive, as encrypted file. The performance burden of asymmetric algorithms is too much to use them for encrypting a large amount of data. The reason why two different algorithms are used is the speed of encryption. The FEK in its own turn is encrypted with a public/private key algorithm (RSA) and stored along with the file. The key, used in symmetric encryption is called File Encryption Key (FEK).
![efs file decryption tool efs file decryption tool](https://cdn3.geckoandfly.com/wp-content/uploads/2019/04/quick-heal-decryption-830x484.jpg)
File data is being encrypted with symmetric algorithm (DESX). Encrypted Files and FoldersĮFS uses symmetric key encryption in combination with public key technology to protect files.