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I would like to password protect or encrypt a directory and all the files within it (for the whole directory tree below it). I do not want to bother the whole home directory, I want a specific directory with some files and folders in it. I would like to be able to encrypt the directory or decrypt it using a password. Command line would be nicest to use. I don't want to have to create a new file as an encrypted version and then, delete the previous ones which are the non-encrypted version.

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Interesting, "without having to create new files"... –  phunehehe Jan 8 '12 at 12:36
    
You mean mount as an encrypted filesystem? –  Faheem Mitha Jan 8 '12 at 12:52
    
@FaheemMitha, I also would like to avoid the filesystem route, it sounds complicated. –  Vass Jan 8 '12 at 13:03
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@Vass The filesystem route is the simplest method by far. You'll make your life easier if you don't reject solutions arbitrarily. –  Gilles Jan 8 '12 at 16:34
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3 Answers

up vote 8 down vote accepted

Use encfs (available as a package on most distributions). To set up:

mkdir ~/.encrypted ~/encrypted
encfs ~/.encrypted ~/encrypted
# enter a passphrase
mv existing-directory ~/encrypted

The initial call to encfs sets up an encrypted filesystem. After that point, every file that you write under ~/encrypted is not stored directly on the disk, it is encrypted and the encrypted data is stored under ~/.encrypted. The encfs command leaves a daemon running, and this daemon handles the encryption (and decryption when you read a file from under ~/encrypted).

In other words, for files under ~/encrypted, actions such as reads and writes do not translate directly to reading or writing from the disk. They are performed by the encfs process, which encrypts and decrypts the data and uses the ~/.encrypted directory to store the ciphertext.

When you've finished working with your files for the time being, unmount the filesystem so that the data can't be accessed until you type your passphrase again:

fusermount -u ~/encrypted

After that point, ~/encrypted will be an empty directory again.

When you later want to work on these files again, mount the encrypted filesystem:

encfs ~/.encrypted ~/encrypted
# enter your passphrase

This, again, makes the encrypted files in ~/.encrypted accessible under the directory ~/encrypted.

You can change the mount point ~/encrypted as you like: encfs ~/.encrypted /somewhere/else (but mount the encrypted directory only once at a time). You can copy or move the ciphertext (but not while it's mounted) to a different location or even to a different machine; all you need to do to work on the files is pass the location of the ciphertext as the first argument to encfs and the location of an empty directory as the second argument.

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the answer is very useful and practical. I would appreciate very much if you could add some more text to explain what each operation is doing if that is not a bother to you. And could you explain what is meant by a filesystem in this context, and the relevance of mounting? –  Vass Jan 8 '12 at 22:50
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@Vass I've updated my answer with more explanations. For background on filesystems and mounting, see What mount points exist on a typical Linux system? and What is meant by mounting a device in Linux? –  Gilles Jan 8 '12 at 23:17
    
That is an amazing explanation. I feel like I learned alot. And the extra links help. So the filesystem made by encfs is 'jumbled up blocks of the original file' and through encfs you can navigate and read it; because the original filesystem is not compatible to use these blocks of data. and the encrypted directory is hidden to not get into it by accident. and if you did you would see nothing? –  Vass Jan 8 '12 at 23:44
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@Vass “the filesystem made by encfs is 'jumbled up blocks of the original file' and through encfs you can navigate and read it”: yes, exactly. The directory ~/.encrypted contains the ciphertext; you can access it without going through encfs, but you'll only see encrypted data there. –  Gilles Jan 8 '12 at 23:48
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I don't want to have to create a new file as an encrypted version and then, delete the previous ones which are the non-encrypted version

But that's exactly the scenario you've described...."be able to encrypt the directory or decrypt it"

I suspect the solution you're looking for is an encrypted FUSE or similar. The filesystem is stored in an encrypted file and when mounted (with a passphrase) there is transparent access via the VFS layer.

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creating a new file and deleting previous is a .zip route with password protection. I don't understand the file system and mounting route you refer to. Is there not some program which jumbles up the file in some way and then can put it back into order? –  Vass Jan 8 '12 at 13:03
    
yes, here a whole list of FUSE encrypted filesystems. The zip path is the simplest –  bdowning Jan 8 '12 at 13:09
    
@Vass I don't understand what you mean by “the zip path”: there's no zip involved. The plaintext is never stored on disk (that would be a lot more complicated and defeat most of the purpose of encryption). –  Gilles Jan 8 '12 at 16:33
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The zip route/zip path is to recursively zip a directory with the encryption/password option(s). Then however, when one wants to access a file, one must extract the unencrypted file from the zip, read file and then delete, or edit file and then update zip with new file, then delete intermediate file. He's seeking the transparency of an encrypted filesystem but at a directory level. I, and others suggest FUSE with an encrypted fs. "Simple" though, is a matter of perspective and experience. –  bdowning Jan 8 '12 at 21:37
    
@bdowning, yes, you articulated it correctly. I do not understand filesystems and their operation. I would work blindly with the commands without understanding the concepts. –  Vass Jan 8 '12 at 22:33
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Note that there are no "contents of a directory", a directory simply associates names with inodes, the same inodes can have lots of other names pointing at them.

What exactly are your trying to do? This is a possible solution, not a problem...

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