# eCryptfs

Related articles

- Disk encryption

This article describes basic usage of eCryptfs. It guides you through the process of creating a private and secure encrypted directory within your $HOME directory, where you can store all your sensitive files and private data.

In implementation eCryptfs differs from dm-crypt, which provides a block device encryption layer, while eCryptfs is an actual file-system – a stacked cryptographic file system to be exact. For comparison of the two you can refer to this table .

The summary is that it doesn't require special on-disk storage allocation effort, such as separate partitions, you can mount eCryptfs on top of any single directory to protect it. That includes e.g. your entire $HOME and network file systems (i.e. having encrypted NFS shares). All cryptographic metadata is stored in the headers of files, so encrypted data can be easily moved, stored for backup and recovered. There are other advantages, but there are also drawbacks, for instance eCryptfs is not suitable for encrypting complete partitions which also means you can't protect your swap space with it (instead you can combine it with dm-crypt).

For more details on how eCryptfs compares to other disk encryption solutions, see Disk encryption#Comparison table.

Note: The article is currently in the process of being re-structured. If you can help with the task, that would be great - have a look at the plan. If you need to find information that might not be in its place again, the revision before the restructuring is here.

## Basics

See Disk encryption#Available_methods for a general introduction to stacked filesystem encryption, and how it compares to block device encryption.

## Preparation

Before starting to set up disk encryption, there are a few things to consider and to prepare in advance: Disk encryption#Preparation

### Deficiencies

As of kernel 3.14.1, eCryptfs does not handle sparse files. This should be considered before encrypting large portions of the directory structure ($HOME, for example). For most intents and purposes this deficiency does not pose a problem. Using eCryptfs to encrypt sparse files, however, currently encrypts the entire allocated space of the sparse file, which, in the case of big files, can starve the system of resources. (This bug may be tracked on Launchpad). One popular and inadvisable application of eCryptfs is to encrypt a BitTorrent download location; this often requires eCryptfs to handle sparse files of 10 GB or more and may lead to intense disk starvation. A simple workaround is to place sparse files in an unencrypted .Public directory (as opposed to the standard eCryptfs .Private directory, explained below).

### Login password

Note: With shadow 4.1.4.3-3 sha512 is the default for new passwords (see bug 13591 and corresponding commit).

If you are encrypting your whole home, with auto-mounting you should use a strong password and consider changing the hash algorithm for /etc/shadow from md5 to stronger ones like sha512/bcrypt that helps to protect your password against rainbow-table attacks. See https://wiki.archlinux.org/index.php/SHA_password_hashes for more information.

## Setup & Mounting

eCryptfs is a part of Linux since version 2.6.19. But to work with it you will need the userspace tools provided by the package ecryptfs-utils available in the Official repositories.

Once you have installed that package you can load the ecryptfs module and continue with the setup:

    # modprobe ecryptfs

Before we say anything else it's advised that you check the eCryptfs documentation. It is distributed with a very good and complete set of manual pages.

### Using the Ubuntu tools

Most of the user-friendly convenience tools installed by the ecryptfs-utils package assume a very specific eCryptfs setup, namely the one that is officially used by Ubuntu (where it can be selected as an option during distro installation). Unfortunately, these choices are not just default options but are actually hard-coded in the tools, so if this set-up does not suit your needs then you can't use the convenience tools and will have to follow the steps at #Manual_setup instead.

The set-up used by these tools is as follows:

each user can have only one encrypted directory that is managed by these tools: either full $HOME dir encryption... or a single encrypted data directory (by default `~/Private/`, but this can be customized). the lower directory for each user is always `~/.Private/` (in the case of full home dir encryption, this will be a symlink to the actual location at `/home/.ecryptfs/$USER/.Private/`) the encryption options used are: cipher: AES key length: 16 bytes (128 bits) key management scheme: passphrase plaintext passthrough: enabled the configuration / control info for the encrypted directory is stored in a bunch of files at `~/.ecryptfs/`: (in the case of full home dir encryption, this will be a symlink to the actual location at `/home/.ecryptfs/$USER/.ecryptfs/`) `Private.mnt` [plain text file] - contains the path where the upper directory should be mounted (e.g. `/home/lucy` or `/home/lucy/Private`) `Private.sig` [plain text file] - contains the signature used to identify the mount passphrase in the kernel keyring `wrapped-passphrase` [binary file] - the mount passphrase, encrypted with the login passphrase `auto-mount`, `auto-umount` [empty files] - if they exist, the pam_ecryptfs.so module will (assuming it is loaded) automatically mount/unmount this encrypted directory when the user logs in/out

#### Encrypting a data directory

For a full $HOME directory encryption see #Encrypting a home directory

To encrypt a single data directory as a user, run

    $ ecryptfs-setup-private

and follow the instructions. It will automatically create the ~/.Private/ and ~/.ecryptfs/ directory structures as described in the box above. It will also ask for two passphrases:

login passphrase
  This is the password you will have to enter each time you want to mount the encrypted directory. If you want auto-mounting on login to work, it has to be the same password you use to login to your user account; otherwise you can choose a different one.

mount passphrase
  This is used to derive the actual file encryption master key. Thus you should not enter a custom one unless you know what you are doing - instead press Enter to let it auto-generate a random one, which will be much more secure. It will be encrypted using the login passphrase and stored in this encrypted form in `~/.ecryptfs/wrapped-passphrase`, and automatically decrypted ("unwrapped") again in RAM when needed, so you never have to enter it manually. Make sure this file does not get lost, otherwise you can never access your encrypted folder again! You may want to run `ecryptfs-unwrap-passphrase` to see the mount passphrase in unencrypted form, write it down on a piece of paper, and keep it in a safe (or similar), so you can use it to recover your encrypted data in case the wrapped-passphrase file is accidentally lost/corrupted or in case you forget the login passphrase.

The mount point ("upper directory") for the encrypted folder will be at `~/Private` by default, however you can manually change this right after the setup command has finished running, by doing:

    $ mv ~/Private /path/to/new/folder
    $ echo /path/to/new/folder > ~/.ecryptfs/Private.mnt

To actually use your encrypted folder, you will have to mount it... See #Mounting below.

##### Undo encryption

To undo the single directory encryption run

    $ ecryptfs-setup-private --undo

and follow the instructions

#### Encrypting a home directory

This will set up an encrypted $HOME directory for a user, and take care of migrating any existing files they have in their not yet encrypted home directory. Ensure that the user in question owns no processes and is logged out. You also need to ensure that you have rsync installed. Once the prerequisites have been met run as root:

    # ecryptfs-migrate-home -u username

and follow the instructions. It is imperative that the user logs in before the next reboot, to complete the process.

#### Mounting

#### Auto-mounting

A better way is to use PAM directly, see 'PAM MODULE' in:

    /usr/share/doc/ecryptfs-utils/README

1. Check if ~/.ecryptfs/auto-mount and ~/.ecryptfs/wrapped-passphrase (these are automatically created by ecryptfs-setup-private) exist.

2. Add ecryptfs to the pam-stack exactly as following to allow transparent unwrapping of the passphrase on login.

Open /etc/pam.d/system-auth and add this after the line containing auth required pam_unix.so [...]:

    auth	required	pam_ecryptfs.so unwrap

, then add this above the line containing password required pam_unix.so [...]:

    password	optional	pam_ecryptfs.so

, and this after the line session required pam_unix.so:

    session	optional	pam_ecryptfs.so

3. Relogin (you need to type the user's password for obvious reason ;) and check output of mount which should now contain a mountpoint, e.g.:

    /home/$USER/.Private on /home/$USER/Private type ecryptfs (...)

Your user's encrypted directory should be perfectly readable, e.g. $HOME/Private/

Note that the latter will be automatically unmounted and made unavailable when the user log off.

To use the eCryptfs PAM module it self for mounting you should know it depends on some hard-coded Ubuntu defaults. Like using AES cipher with a 16 byte key. As described in this BBS post [1] you have to do the following steps:

1) For your understanding and preparation, read the guide mentioned above. [2]

2) Install keyutils and ecryptfs-utils from the official Repos.

[Do the following steps as root!]

3) Make a "ecryptfs" Group:

    groupadd ecryptfs

4) Add the user to it:

    usermod -aG ecryptfs user

5) Load the ecryptfs module

    modprobe ecryptfs

6) Change your /etc/pam.d/system-auth to look something like this (lines to add are bold):

    #%PAM-1.0

    auth      required  pam_env.so
    auth      required  pam_unix.so     try_first_pass nullok
    auth      required  pam_ecryptfs.so unwrap
    auth      optional  pam_permit.so

    account   required  pam_unix.so
    account   optional  pam_permit.so
    account   required  pam_time.so

    password  required  pam_ecryptfs.so
    password  required  pam_unix.so     try_first_pass nullok sha512 shadow
    password  optional  pam_permit.so

    session   required  pam_ecryptfs.so unwrap
    session   required  pam_limits.so
    session   required  pam_env.so
    session   required  pam_unix.so
    session   optional  pam_permit.so

6a) When using GDM < 3.2 to log in, edit /etc/pam.d/gdm like this:

    #%PAM-1.0
    auth            requisite       pam_nologin.so
    auth            required        pam_env.so
    auth            required        pam_unix.so
    auth            optional        pam_ecryptfs.so unwrap
    auth            optional        pam_gnome_keyring.so
    account         required        pam_unix.so
    session         required        pam_limits.so
    session         required        pam_unix.so
    session         optional        pam_ecryptfs.so unwrap
    session         optional        pam_gnome_keyring.so auto_start
    password        required        pam_unix.so
    password        optional        pam_ecryptfs.so

6b) For GDM >= 3.2, make the following changes to /etc/pam.d/gdm-password (thanks to grawity for this):

    #%PAM-1.0
    auth            requisite       pam_nologin.so
    auth            required        pam_env.so
    auth            requisite       pam_unix.so nullok
    auth            optional        pam_ecryptfs.so unwrap
    auth            optional        pam_gnome_keyring.so
    auth            sufficient      pam_succeed_if.so uid >= 1000 quiet
    auth            required        pam_deny.so
    account         required        pam_unix.so
    password        required        pam_unix.so
    password        optional        pam_ecryptfs.so
    session         required        pam_loginuid.so
    -session        optional        pam_systemd.so
    session         optional        pam_keyinit.so force revoke
    session         required        pam_limits.so
    session         required        pam_unix.so
    session         optional        pam_ecryptfs.so unwrap
    session         optional        pam_gnome_keyring.so auto_start

6c) For KDM, make the following changes to /etc/pam.d/kde:

    #%PAM-1.0
    auth            required        pam_unix.so
    auth            optional        pam_ecryptfs.so unwrap
    auth            required        pam_nologin.so
    account         required        pam_unix.so
    password        optional        pam_ecryptfs.so
    password        required        pam_unix.so
    session         required        pam_unix.so
    session         optional        pam_ecryptfs.so unwrap
    session         required        pam_limits.so

6d) For LXDM, make the following changes to /etc/pam.d/lxdm:

    #%PAM-1.0
    auth            requisite       pam_nologin.so
    auth            required        pam_env.so
    auth            required        pam_unix.so
    auth            optional        pam_ecryptfs.so unwrap
    account         required        pam_unix.so
    session         required        pam_limits.so
    session         required        pam_unix.so
    session         optional        pam_ecryptfs.so unwrap
    password        required        pam_unix.so
    password        optional        pam_ecryptfs.so

6e) For LightDM, make the following changes to /etc/pam.d/lightdm

    #%PAM-1.0
    auth      required pam_nologin.so
    auth      required pam_env.so
    auth      required pam_unix.so
    auth      optional pam_ecryptfs.so unwrap
    account   required pam_unix.so
    password  optional pam_ecryptfs.so
    password  required pam_unix.so
    session   required pam_unix.so
    session   optional pam_ecryptfs.so unwrap

7) To be able to automatically mount your encrypted home directory on login using SSH, edit /etc/pam.d/sshd:

    #%PAM-1.0
    #auth           required        pam_securetty.so        #Disable remote root
    auth            required        pam_unix.so
    auth            optional        pam_ecryptfs.so unwrap
    auth            required        pam_env.so
    account         required        pam_nologin.so
    account         required        pam_unix.so
    account         required        pam_time.so
    password        required        pam_unix.so
    password        optional        pam_ecryptfs.so
    session         optional        pam_ecryptfs.so unwrap
    session         required        pam_unix_session.so
    session         required        pam_limits.so
    session         optional        pam_ck_connector.so nox11

9) Log in and check if everything worked correctly.

This is a working solution and ecryptfs is exactly used as in Ubuntu (10.04/10.10) - and is easy to set up. Besides this, it has the advantage of auto-unmount at log-out, which shell profile files (i.e. `~/.bash_logout`) could have trouble doing, because there could still be open file-descriptors by the shell at the time of umount. To encrypt swap, see: Dm-crypt/Swap encryption (some of the tools provided by ecryptfs, such as ecryptfs-setup-swap, only work in ubuntu).

### Using ecryptfs-simple

Use ecryptfs-simple if you just want to use eCryptfs to mount arbitrary directories the way you can with EncFS. ecryptfs-simple does not require root privileges or entries in fstab, nor is it limited to hard-coded directories such as ~/.Private. The package is available in the AUR and in Xyne's repos.

As the name implies, usage is simple:

    # simple mounting
    ecryptfs-simple /path/to/foo /path/to/bar

    # automatic mounting: prompts for options on the first mount of a directory then reloads them next time
    ecryptfs-simple -a /path/to/foo /path/to/bar

    # unmounting by source directory
    ecryptfs-simple -u /path/to/foo

    # unmounting by mountpoint
    ecryptfs-simple -u /path/to/bar

### Manual setup

#### With ecryptfs-utils

Alternatively to using the scripts `ecryptfs-setup-private` and `ecryptfs-mount-private` to setup and mount eCryptfs, the same can be done directly with the binaries (which those scripts use) `ecryptfs-add-passphrase` and `mount.ecryptfs_private` from the package `ecryptfs-utils`. Those binaries require no root privileges to work, by default.

First choose an ALIAS as you like. Through this section, ALIAS will be `secret`. Create the required directories/files:

    $ mkdir ~/.secret ~/secret ~/.ecryptfs
    $ touch ~/.ecryptfs/secret.conf ~/.ecryptfs/secret.sig

The `~/.secret` directory will hold the encrypted data. The `~/secret` directory is the mount point where `~/.secret` will be mounted as an ecryptfs filesystem.

In the next command, replace USER with the name of the current user's home directory. Note that you should write full paths to `~/.ecryptfs/secret.conf`. Its format looks like the one of `/etc/fstab` without the mount options:

    $ echo "/home/USER/.secret /home/USER/secret ecryptfs" > ~/.ecryptfs/secret.conf

A mount passphrase must be added to the keyring:

    $ ecryptfs-add-passphrase
    Passphrase:
    Inserted auth tok with sig [78c6f0645fe62da0] into the user session keyring

Write the output signature (ecryptfs_sig) from the previous command to `~/.ecryptfs/secret.sig`:

    $ echo 78c6f0645fe62da0 > ~/.ecryptfs/secret.sig

A second passphrase for filename encryption may be used. If you choose so, add it to the keyring:

    $ ecryptfs-add-passphrase
    Passphrase:
    Inserted auth tok with sig [326a6d3e2a5d444a] into the user session keyring

If you run the command above, append its output signature (ecryptfs_fnek_sig) to `~/.ecryptfs/secret.sig`:

     $ echo 326a6d3e2a5d444a >> ~/.ecryptfs/secret.sig

Finally, to mount `~/.secret` on `~/secret`:

    $ mount.ecryptfs_private secret

An ecryptfs filesystem will be mounted with the following options:

    rw,nosuid,nodev,relatime,ecryptfs_fnek_sig=326a6d3e2a5d444a,ecryptfs_sig=78c6f0645fe62da0,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs

Except for `ecryptfs_sig` and `ecryptfs_fnek_sig`, the options are hard-coded. `ecryptfs_fnek_sig` will exist only if you choose filename encryption.

To unmount `~/.secret`:

    $ umount.ecryptfs_private secret

#### Without ecryptfs-utils

The ecryptfs-utils package is distributed with a few helper scripts which will help you with key management and similar tasks. Some were written to automate this whole process of setting up encrypted directories (ecryptfs-setup-private) or help you combine eCryptfs with dm-crypt to protect swap space (ecryptfs-setup-swap). Despite those scripts we will go trough the process manually so you get a better understanding of what is really being done.

First create your private directories, in this example we will call them exactly that: Private

    $ su -
    # mkdir -m 700 /home/username/.Private
    # mkdir -m 500 /home/username/Private
    # chown username:username /home/username/{.Private,Private}

Let's summarize

- Actual encrypted data will be stored in ~/.Private directory (so-called lower directory)
- While mounted, decrypted data will be available in ~/Private directory (so-called upper directory)
  - While not mounted nothing can be written to this directory
  - While mounted it has the same permissions as the lower directory

eCryptfs can now be mounted on top of ~/Private.

    # mount -t ecryptfs /home/username/.Private /home/username/Private

You will need to answer a few questions and provide a passphrase which should be used to mount this directory in the future. However you can also have different keys encrypting different data (more about this below). For convenience we will limit this guide to only one key and passphrase. Let's see an example:

    Key type: passphrase
    Passphrase: ThisIsAVeryWeakPassphrase
    Cipher: aes
    Key byte: 16
    Plaintext passtrough: no
    Filename encryption: no
    Add signature to cache: yes

Let's summarize

- The passphrase is your mount passphrase which will be salted, hashed and loaded into the kernel keyring.
  - In eCryptfs terms, this salted, hashed passphrase is your "file encryption key, encryption key", or fekek.
- eCryptfs supports a few different ciphers (AES, blowfish, twofish...). You can read about them on Wikipedia.
- Plaintext passtrough enables you to store and work with un-encrypted files stored in the lower directory.
- Filename encryption is available since Linux 2.6.29
  - In eCryptfs terms the key used to protect filenames is known as "filename encryption key", or fnek.
- The signature of the key(s) will be stored in `/root/.ecryptfs/sig-cache.txt`.

Since our later goal is to be able to mount without root privileges, we will now move the eCryptfs configuration directory to your own home and transfer the ownership to you:

    # mv /root/.ecryptfs /home/username
    # chown username:username /home/username/.ecryptfs

Your setup is now complete and directory is mounted. You can place any file in the ~/Private directory and it will get encrypted in ~/.Private.

Now copy a few files to your new private directory, and then un-mount it. If you inspect the files you will see that they are unreadable – encrypted. That was cool you say, but how do I get them back... and that brings us to:

Above is detailed the simplest way to setup the mount point, but ecryptfs-setup-private runs through some extra steps.

- The above mount passphrase is derived from the passphrase you type in. This is not considered very secure, so the setup script grabs some characters from `/dev/random` for safety:

    od -x -N $bytes --width=$bytes /dev/urandom | head -n 1 | sed "s/^0000000//" | sed "s/\s*//g"

- ecryptfs-setup-private also takes the resulting mount passphrase and wraps it with your login passphrase (pasword) and stores this in ~/.ecryptfs/wrapped-passphrase. You can replicate this with:

    $ ecryptfs-wrap-passphrase ~/.ecryptfs/wrapped-passphrase
      Passphrase to wrap:
      Wrapping passphrase:

##### Mounting

Whenever you need your files available you can repeat the above mount procedure, using the same passphrase and options if you want to access your previously encrypted files or using a different passphrase (and possibly options) if for some reason you want to have different keys protecting different data (imagine having a publicly shared directory where different data is encrypted by different users, and their keys).

In any case going trough those questions every time could be a bit tedious.

One solution would be to create an entry in the `/etc/fstab` file for this mount point:

    /home/user/.Private /home/user/Private ecryptfs [... user ... ecryptfs_sig=XY,ecryptfs_cipher=aes,ecryptfs_key_bytes=16,ecryptfs_unlink_sigs 0 0

- You will notice that we defined the user option, it enables you to mount the directory as a user (if it does not works as a normal user, you may need to setuid mount.ecryptfs by running as root: chmod +s /sbin/mount.ecryptfs)
- Notice the ecryptfs_sig option, replace XY with your own key signature (as seen in the mtab line earlier and in `sig-cache.txt`)
- If you enabled filename encryption then pass an additional mount option: ecryptfs_fnek_sig=XY, where XY is the same signature you provide with the ecryptfs_sig option.
- Last option ecrypfs_unlink_sigs ensures that your keyring is cleared every time the directory is un-mounted

Since your key was deleted from the kernel keyring when you un-mounted, in order to mount you need to insert it into the keyring again. You can use the ecryptfs-add-passphrase utility or the ecryptfs-manager to do it:

When the key is inserted you can mount the directory:

    $ ecryptfs-add-passphrase
      Passphrase: ThisIsAVeryWeakPassphrase

    $ mount -i /home/username/Private

You will notice that we used the `-i` option this time. It disables invoking the mount helper. Speaking of which, using `-i` by default mounts with: nosuid, noexec and nodev. If you want to have at least executable files in your private directory you can add the exec option to the fstab line.

This would be a good place to mention the keyctl utility from the (earlier installed) keyutils package. It can be used for any advanced key management tasks. Following examples show how to list your keyring contents and how to clear them:

    $ keyctl list @u
    $ keyctl clear @u

Note: However, one should remember that /etc/fstab is for system-wide partitions only and should not be used for user-specific mounts

##### Auto-mounting

The above "eCryptfs and $HOME" article uses a shell init file to mount the home directory. The same can be done using pam_mount with the added benefit that home is un-mounted when all sessions are logged out. Add the following lines to `/etc/security/pam_mount.conf.xml`:

    <luserconf name=".pam_mount.conf.xml" />
    <mntoptions require="" />
    <lclmount>mount -i %(VOLUME) "%(before=\"-o\" OPTIONS)"</lclmount>

Please prefer writing manually these lines instead of simply copy/pasting them (especially the lclmount line), otherwise you might get some corrupted characters. Explanation:

- the first line indicates where the user-based configuration file is located (here `~/.pam_mount.conf.xml`) ;
- the second line overwrites the default required mount options which are unnecessary ("nosuid,nodev") ;
- the last line indicates which mount command to run (eCryptfs needs the `-i` switch).

Then set the volume definition, preferably to `~/.pam_mount.conf.xml`:

    <pam_mount>
        <volume noroot="1" fstype="ecryptfs" path="/home/.ecryptfs/user/.Private/" mountpoint="/home/user/"/>
    </pam_mount>

"noroot" is needed because the encryption key will be added to the user's keyring

Finally, edit `/etc/pam.d/login` as described in pam_mount's article.

###### Optional step

To avoid wasting time needlessly unwrapping the passphrase you can create a script that will check pmvarrun to see the number of open sessions:

    #!/bin/sh
    #
    #    /usr/local/bin/doecryptfs

    exit $(/usr/sbin/pmvarrun -u$PAM_USER -o0)

With the following line added before the eCryptfs unwrap module in your PAM stack:

    auth    [success=ignore default=1]    pam_exec.so     quiet /usr/local/bin/doecryptfs
    auth    required                      pam_ecryptfs.so unwrap

The article suggests adding these to `/etc/pam.d/login`, but the changes will need to be added to all other places you login, such as `/etc/pam.d/kde`.

## Usage

Besides using your private directory as storage for sensitive files, and private data, you can also use it to protect application data. Take Firefox for an example, not only does it have an internal password manager but the browsing history and cache can also be sensitive. Protecting it is easy:

     $ mv ~/.mozilla ~/Private/mozilla
     $ ln -s ~/Private/mozilla ~/.mozilla

### Removal

If you want to move a file out of the private directory just move it to it's new destination while ~/Private is mounted. Also note that there are no special steps involved if you want to remove your private directory. Make sure it is un-mounted and delete ~/.Private, along with all the files.

### Backup

Setup explained here separates the directory with encrypted data from the mount point, so the encrypted data is available for backup at any time. With an overlay mount (i.e. ~/Secret mounted over ~/Secret) the lower, encrypted, data is harder to get to. Today when cronjobs and other automation software do automatic backups the risk of leaking your sensitive data is higher.

We explained earlier that all cryptographic metadata is stored in the headers of files. You can easily do backups, or incremental backups, of your ~/.Private directory, treating it like any other directory.

## See Also

- Security audit of eCryptfs by Taylor Hornby (January 22, 2014).

This wiki article covers only the basic setup of a private encrypted directory. There is however another article about eCryptfs on Arch Linux, which covers encryption of your entire $HOME and encrypting swap space without breaking hibernation (suspend to disk).

That article includes many more steps (i.e. using PAM modules and automatic mounting) and the author was opposed to replicating it here, because there is just no single "right" way to do it. The author proposes some solutions and discusses the security implications, but they are his solutions and as such might not be the best nor are they endorsed by the eCryptfs project in any way.

    Article: eCryptfs and $HOME by Adrian C. (anrxc).

Consider that Chromium OS, as released by Google, is using eCryptfs to protect devices that are, and will be, powered by it. Some implementation details are available and they make excellent reading. You can read them here, they could help a lot as you're coming up with your own strategy.

Categories:

- Security
- File systems