Encryption is Not Enough | Gizmo’s Freeware

A few facts

Inconvenient fact #1 - Cryptography is harder than it looks: Not just any encryption program will do. Most any competent programmer could grab the open-source code for a block cipher (cryptographic protocol) -- say AES -- and put together an encryption process to get from password entry to ciphertext.

But there is a special Murphy's Law for budding cryptographers: Somewhere else in the naive coder's encryption process - key generation, random number generation, hash processes, etc. - there will almost certainly be one or more fatal flaws. A skilled hacker can often find and break process vulnerabilities without much effort. Do-it-yourself encryption is much like thinking you could be competitive with Bobby Fischer or Garry Kasparov [more]

As Bruce Schneier puts it in Security Pitfalls in Cryptography:

A recent highly visible example shows that it's hard to know who's expertise to trust. [discussion] [examples of cryptographic vulnerabilities]

#2: Use of proprietary, closed-source cryptology leads to persistent folly:

#3 - Operating systems are messy: They leave behind echoes (cleartext) of the data you access or process - swap files, temp files, hibernation files, browser cache files, and other artifacts.

Windows Volume Shadow Copy Service presents a special problem. Even if you wipe the file after encrypting it, the cleartext copy of previous versions remain on the drive. Even though they are hidden, it is easy enough to find and restore them.

Many simple encryption programs simply encrypt from and/or decrypt to a cleartext file. Yes, some of them delete the cleartext file after you close the program, but they may not securely purge the file (make it unrecoverable).

Using a compression -- e.g. Zip -- program for encryption can be particularly hazardous. Unless you can create, open and save files directly in the encrypted archive you'll leave clear-text version of files behind on the host computer. You must purge (not just delete) those working files. You did know that deleted files are not actually erased didn't you?

If you lose your computer, or if anyone - burglar, snatch thief, snoopy co-worker - gains access to your computer, running or not, they are likely to find cleartext echoes of your encrypted data. You may want to use full-drive encryption to prevent that. All those cleartext echoes will be encrypted when your computer is off. Be sure your program also encrypts the whole hard drive when your laptop lid is closed, not just when you turn it off.

#4: Any encryption program can have a secret backdoor: The backdoor may simply be there to assist in recovery and other administrative functions. Some encryption is known to have mandated or coerced backdoors imposed by various government entities. There is just no way to know for sure if that is the case or not for any particular encryption solution. If there is a backdoor for any purpose, it is often easily discovered and exploited by attackers. Game over.

#5: Malware presents yet another threat: If any computer you use to access your data is infected by spyware, the cleartext (decrypted) data can easily be accessed and transmitted to an exploiter over the Internet. Encryption doesn't do a thing for you in this case. Your computer security system (or lack thereof) is what has let you down.

Final worry: Your computer and/or storage devices may be subject to search. It may be better to not have your sensitive data with you if you're traveling by air. Consider storing your data in the cloud (online in encrypted form) or accessing it over a VPN when you need it.

My evaluation of Pismo File Mount Audit Package provides a useful example of my approach tovetting encryption solutions.

I like the Private Folder feature of this audit package. It allows you to quickly access an encrypted file that you convert to an encrypted folder using a context menu command in Windows Explorer. The advantage is that you read and write direcctly to this folder, thus avoiding the problem of plain-text residue on your hard drive. But the critical question is the encryption trustworthy?

Fatal backup trap:

Encryption programs that create encrypted "volumes" (files that contain encrypted files) whose file size does not change, and they often intentionally do not change "date modified", even though files in the volume have been changed or added. The purpose is to maintain plausible deniability. But the result can be that your backup system will not recognize that the volume file has changed, and will skip it in the backup. Some encryption products offer an option like, "Preserve modification timestamp of file containers." Unchecking that option will allow the "date modified" to change.

VeraCrypt and TrueCrypt are examples of programs that by default do not change the modified date. However, a few cloud backup services - Dropbox for example - check the hash value of container files, not the date, and if that changes Dropbox stores a new copy of the container file.

Related information on the pitfalls of encryption:

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Encryption is Not Enough | Gizmo's Freeware