NTFSDECRYPT(8) System Manager's Manual NTFSDECRYPT(8)
NAME
ntfsdecrypt - decrypt or update NTFS files encrypted according to EFS
SYNOPSIS
ntfsdecrypt [options] -k key.pfx device file
DESCRIPTION
ntfsdecrypt decrypts a file from an unmounted device and print the de-
crypted data on the standard output. It can also update an encrypted
file with the encryption key unchanged.
The NTFS file encryption (known as EFS) uses a two-level encryption :
first, the file contents is encrypted with a random symmetric key, then
this symmetric key is encrypted with the public keys of each of the
users allowed to decrypt the file (RSA public key encryptions).
Three symmetric encryption modes are currently implemented in ntfsde-
crypt : DESX (a DES variant), 3DES (triple DES) and AES_256 (an AES
variant).
All the encrypted symmetric keys are stored along with the file in a
special extended attribute named "$LOGGED_UTILITY_STREAM". Usually, at
least two users are allowed to read the file : its owner and the recov-
ery manager who is able to decrypt all the files in a company. When
backing up an encrypted file, it is important to also backup the corre-
sponding $LOGGED_UTILITY_STREAM, otherwise the file cannot be decrypted,
even by the recovery manager. Also note that encrypted files are
slightly bigger than apparent, and the option "efs_raw" has to be used
when backing up encrypted files with ntfs-3g.
When ntfsdecrypt is used to update a file, the keys and the
$LOGGED_UTILITY_STREAM are kept unchanged, so a single key file has to
be designated.
Note : the EFS encryption is only available in professional versions of
Windows;
OPTIONS
Below is a summary of all the options that ntfsdecrypt accepts. Nearly
all options have two equivalent names. The short name is preceded by -
and the long name is preceded by --. Any single letter options, that
don't take an argument, can be combined into a single command, e.g. -fv
is equivalent to -f -v. Long named options can be abbreviated to any
unique prefix of their name.
-i, --inode NUM
Display or update the contents of a file designated through its
inode number instead of its name.
-e, --encrypt
Update an existing encrypted file and get the new contents from
the standard input. The full public and private key file has to
be designated, as the symmetric key is kept unchanged, so the
private key is needed to extract it.
-f, --force
This will override some sensible defaults, such as not using a
mounted volume. Use this option with caution.
-k, --keyfile-name key.pfx
Define the file which contains the public and private keys in
PKCS#12 format. This file obviously contains the keys of one of
the users allowed to decrypt or update the file. It has to be ex-
tracted from Windows in PKCS#12 format (its usual suffix is .p12
or .pfx), and it is protected by a passphrase which has to be
typed in for the keys to be extracted. This can be the key file
of any user allowed to read the file, including the one of the
recovery manager.
-h, --help
Show a list of options with a brief description of each one.
-q, --quiet
Suppress some debug/warning/error messages.
-V, --version
Show the version number, copyright and license of ntfsdecrypt.
-v, --verbose
Display more debug/warning/error messages.
EXAMPLES
Display the contents of the file hamlet.doc in the directory Documents
of the root of the NTFS file system on the device /dev/sda1
ntfsdecrypt -k foo.key /dev/sda1 Documents/hamlet.doc
Update the file hamlet.doc
ntfsdecrypt -k foo.key /dev/sda1 Documents/hamlet.doc < new.doc
BUGS
There are no known problems with ntfsdecrypt. If you find a bug please
send an email describing the problem to the development team:
ntfs-3g-devel@lists.sf.net
AUTHORS
ntfsdecrypt was written by Yuval Fledel, Anton Altaparmakov and Yura
Pakhuchiy. It was ported to ntfs-3g by Erik Larsson and upgraded by
Jean-Pierre Andre.
AVAILABILITY
ntfsdecrypt is part of the ntfs-3g package and is available from:
https://github.com/tuxera/ntfs-3g/wiki/
SEE ALSO
Read ntfs-3g(8) for details on option efs_raw,
ntfscat(8), ntfsprogs(8)
ntfs-3g 2022.10.3 June 2014 NTFSDECRYPT(8)
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