With Windows XP, Windows Server 2003 and Windows Vista you can use the Cipher.exe command line tool to encrypt and decrypt files and folders. This is handy for scripts and/or just to know that you have actually encrypted something if you are a command line freak!
However there is another hidden use that lays within Cipher.exe – the ability to overwrite data that you have deleted so that it cannot be recovered or accessed. See the below examples and a link to the MS KB page about this function.
To encrypt a folder use the following command with Cipher.exe:
E:>cipher /E /S:e:temp
To Decrypt this folder, use this syntax:
E:>cipher /D /S:e:temp
How to Use the Cipher Security Tool to Overwrite Deleted Data
To overwrite deleted data on a volume by using Cipher.exe, use the /w switch with the cipher command:
The above command causes all de-allocated space on drive E to be overwritten.
Data that is not allocated to files or folders is overwritten and this permanently removes the data.
Cipher syntax and switches:
CIPHER [/E | /D] [/S:directory] [/A] [/I] [/F] [/Q] [/H] [pathname […]]
CIPHER /U [/N]
CIPHER /X[:efsfile] [filename]
/A Operates on files as well as directories. The encrypted file
could become decrypted when it is modified if the parent
directory is not encrypted. It is recommended that you encrypt
the file and the parent directory.
/D Decrypts the specified directories. Directories will be marked
so that files added afterward will not be encrypted.
/E Encrypts the specified directories. Directories will be marked
so that files added afterward will be encrypted.
/F Forces the encryption operation on all specified objects, even
those which are already encrypted. Already-encrypted objects
are skipped by default.
/H Displays files with the hidden or system attributes. These
files are omitted by default.
/I Continues performing the specified operation even after errors
have occurred. By default, CIPHER stops when an error is
/K Creates new file encryption key for the user running CIPHER. If
this option is chosen, all the other options will be ignored.
/N This option only works with /U. This will prevent keys being
updated. This is used to find all the encrypted files on the
/Q Reports only the most essential information.
/R Generates an EFS recovery agent key and certificate, then writes
them to a .PFX file (containing certificate and private key) and
a .CER file (containing only the certificate). An administrator
may add the contents of the .CER to the EFS recovery policy to
create the recovery agent for users, and import the .PFX to
recover individual files.
/S Performs the specified operation on directories in the given
directory and all subdirectories.
/U Tries to touch all the encrypted files on local drives. This will
update user’s file encryption key or recovery agent’s key to the
current ones if they are changed. This option does not work with
other options except /N.
/W Removes data from available unused disk space on the entire
volume. If this option is chosen, all other options are ignored.
The directory specified can be anywhere in a local volume. If it
is a mount point or points to a directory in another volume, the
data on that volume will be removed.
/X Backup EFS certificate and keys into file filename. If efsfile is
provided, the current user’s certificate(s) used to encrypt the
file will be backed up. Otherwise, the user’s current EFS
certificate and keys will be backed up.
directory A directory path.
filename A filename without extensions.
pathname Specifies a pattern, file or directory.
efsfile An encrypted file path.
Used without parameters, CIPHER displays the encryption state of
the current directory and any files it contains. You may use multiple
directory names and wildcards. You must put spaces between multiple
Microsoft Support KB Article 814599
HOW TO: Use Cipher.exe to Over
write Deleted Data in Windows Server 2003