Good (free) encryption... without any trouble ?

[Armando]

I lost a whole day of work. I was using AXcrypt to encrypt certain files and when my computer crashed the files where still in AXcrypt cache folder. So.... guess what happened next ? When I opened one of my encrypted files, it just erased the cache containing at least three important not backed up files, and showed me the old -- so old --  file ! 
I guess I should get into the habit of closing my documents more often -- so that AXcrypt re-encrypts the "cache files" and replaces the old one !! -- but it's not always convenient.

Since I don't want that to ever happen again, I'm thinking of finding another solution.

Advices ?

Thanks !

[Nighted]

You could try TrueCrypt.

[Armando]

I guess I must be unlucky... Last time I tried TrueCrypt, I got BSODs... Driver incompatibilities of some sort.
I could try it again and see.

In the mean time, I'll change some of my backup strategies and make incremental backups of the AXcrypt temp folder. Securitywise though, it's not that great...

[f0dder]

A solution like AxCrypt that decrypts your documents to plaintext to edit them and then does re-encrypt and wipes the plaintex isn't going to be super safe anyway. Sounds weird that you've had BSODs from TrueCrypt, I've always thought it was a pretty stable product... are you running Win9x by any chance?

<shameless_self_promotion>If you just need .txt file encryption, you could check out http://fsekrit.donationcoder.com </shameless_self_promotion>

[Armando]

are you running Win9x by any chance?

No, I'm actually running windows 3.1. 

On a serious note, I don't know why I had problems with truecrypt in the past, but I must say that my main goal was to get to work ASAP, so I didn't play with it to much. I might try it again in a few weeks and see.

If you just need .txt file encryption, you could check out http://fsekrit.donationcoder.com

Good idea for small notes. But I'm working on huge word documents right now.

A solution like AxCrypt that decrypts your documents to plaintext to edit them and then does re-encrypt and wipes the plaintex isn't going to be super safe anyway.

Yup. That's for sure. There's room for [human or machine] mistakes. But I don't know any tool that's as easy to use.

In any case : I guess that — of course — a good advice to AXCrypt users who got a computer crash would be to just recuperate the files right after reboot (that is… if the temp folder is not automatically wiped by some other software), or, as I've tried yesterday (after another BSOD...) :

**booting from a linux LiveCD or partition (I had PCLinuxOS and Ubuntu installed), copy the files before they're wiped, and bingo !!**

That's one workaround. 

More about encryption software later...

[Armando]

[A few months later]

OK. Definitive end of AxCrypt.  I lost some valuable data after MS Word crashed. Axcrypt wiped the files before it was recovered by word, and so...

are solutions like truecrypt or folder lock "crash proof" (for example : would a crash in MS Word make the file unrecoverable if encrypted with one of these encryption tool, or would the encryption have absolutely no effect on the file recovery?)

Thanks for any advice...

[Armando]

This is not very reassuring :

A: In encrypted data, one corrupted bit usually corrupts the whole ciphertext block in which it occurred. The ciphertext block size used by TrueCrypt is 16 bytes (i.e., 128 bits). The mode of operation used by TrueCrypt ensures that if data corruption occurs within a block, the remaining blocks are not affected.

Due to hardware or software errors/malfunctions, files stored on a TrueCrypt volume may become corrupted. Therefore, we strongly recommend that you backup all your important files regularly (this, of course, applies to any important data, not just to encrypted data stored on TrueCrypt volumes). If you do not have enough free space to backup all files, we highly recommend that you at least backup the volume header, which contains the master key (size of the backup file will be 1024 bytes). If a volume header is damaged, the volume is, in most cases, impossible to mount. To backup a volume header, click Tools -> Backup Volume Header.

See also the question 'What do I do when the encrypted filesystem on my TrueCrypt volume is corrupted?'

Of course, what I don't know is if the chances of corruption (in cases of hardware or software errors/malfunctions) are higher -- due to encryption --... or not.

[Armando]

OK. I just realised that MS Word encryption got better over the years. 

Anybody here knows if the (native) advanced security options in MS Word (which allows to choose AES and RSA encryption) are any good?

[mwb1100]

Due to hardware or software errors/malfunctions, files stored on a TrueCrypt volume may become corrupted. Therefore, we strongly recommend that you backup all your important files regularly (this, of course, applies to any important data, not just to encrypted data stored on TrueCrypt volumes).

-Armando (August 30, 2007, 12:07 PM)

Note what it says about "applies to any important data".  One could just as easily say "Due to hardware or software errors/malfunctions, files stored on a disc drive may become corrupted".  In other words, you must have a backup for any important data, whether encrypted or not.  The key issue that encryption adds is that it may make trying to recover non-backed up data more difficult (or impossible). With corruption on non-encrypted data, you often have a good chance of recovering at least some of your document (or whatever) by simply copying out whatever bits might not be corrupted.  This is often impossible with encrypted data.

Also, with encrypted data, you have to have a good system for backing up keys.  On forums for software with encryption support there are always posts of the nature, "how do I get my data back if I've lost my key?".   If the software is any good, the answer will be, "no dice; the data's gone".

As far as TrueCrypt increasing the probability of corruption, that's certainly a possibility, but I must say that my experience has been pretty good.  However, I tend to work in a manner where I copy the files from the TC volume, work on them, then copy back, so I may not be exercising TrueCrypt as much as someone else might.

[Armando]

I see. Thanks!
I'll have to think and weight cons/pros.

Any comments about MS Word's "native" AES and RSA encryption (or others)?

[f0dder]

With encryption you tend to lose a bigger part of your data if a single sectors goes bad, than without encryption - how much will depend on the encryption mode. A common used mode is CBC - chained block cipher - which is usually done in blocks of some size. If a single harddisk sector fails (even a single bit), all data past the corruption of the block the corruption is in will be fubar. A block would typically be 4kb or so.

I haven't really looked into how the LRW mode in TrueCrypt works, so I can't say anything about that.

[Armando]

thanks f0dder.

for the moment I have opted for the "native" MS word encryption; TrueCrypt feels a bit overkill for my needs.

So : some files are encrypted in :
 
"RC4, Microsoft Enhanced DSS and Diffie-Hellman Cryptographic Provider RC4" (128bit), and others in
"Microsoft Enhanced RSA and AES Cryptographic Provider (Prototype)" (128 bit)

there are other encrytion types available :

RC4, Microsoft Base Cryptographic Provider v1.0
RC4, Microsoft Base DSS and Diffie-Hellman Cryptographic Provider
RC4, Microsoft DH SChannel Cryptographic Provider
RC4, Microsoft Enhanced Cryptographic Provider v1.0
RC4, Microsoft RSA SChannel Cryptographic Provider
RC4, Microsoft Strong Cryptographic Provider...

But... it's pretty much all Danish to me. 

what encryption scheme should I use?

[f0dder]

Iirc RC4 has some exploitable flaws, but I dunno if that also pertain to how it's used in MS office. You might want to google around for MS office password crackers and see what's available and how fast it works.

[Armando]

Iirc RC4 has some exploitable flaws, but I dunno if that also pertain to how it's used in MS office. You might want to google around for MS office password crackers and see what's available and how fast it works.

-f0dder (September 01, 2007, 03:27 AM)

Good idea! Thanks for the tip.