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I'd like to encrypt work-related data backups stored on an external drive. The backups contain proprietary company information and trade secrets.

My current backup program, Comodo Backup, allows me to encrypt backup files with AES, Serpent, XOR, and other schemes. However, I've read about vulnerabilities in encryption tools (such as TrueCrypt failing an audit by Google's Project Zero team).

It would be more convenient for me to let CB create encrypted containers, but if necessary, I can have it make uncompressed/unencrypted backups, then encrypt them manually after the fact. Thanks for your help - obviously, my knowledge of security and cryptography is very limited.

Here is the only information I can find regarding their encryption method:

Encryption Algorithms:

3DES - 168-bit/ strong

AES - 128bit / strongest

Blowfish - 64-bit block / strong

DES

Serpent - 128,192 or 256 bit / very strong

Twofish - 128-bit block/ strong

Xor - Variable block size / weak

CBU generates a 32 byte key by applying a SHA256 hash algorithm to the password entered by you. If the encryption algorithm chosen by you requires a key of smaller bit length, the 32 byte key is truncated to the required length. CBU encrypts the backup file with the chosen algorithm using this key. During the restoration the backup file, CBU receives the password entered by you, generates a key by applying the same hash algorithm and uses this key to decrypt the backup file. If a wrong password is entered by someone maliciously, the key required to decrypt the backup could not be generated and the backup could not be restored, ensuring additional level of safety to the backup of your confidential information.

Rather than rely on Comodo Backup to handle the archive encryption, should I use a more specialized tool such as VeraCrypt?

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  • $\begingroup$ You should close your question by restating your question. $\endgroup$ – Alain O'Dea Nov 15 '15 at 20:59
  • $\begingroup$ Regardless of how well it implements the legitimate things in that list, the whole system is severely tarnished by the fact that "XOR" is provided as an option for encryption. That's like seeing an uncooked potato on the menu at a restaurant. $\endgroup$ – Mikero Nov 16 '15 at 5:07
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No, not all encryption tools are made equal.

Even when using the same cryptosystem, say AES-256, a tool's choice of cipher mode, how to generate AAD if present, how to generate IV, how to generate key, and the quality of the random source all affect quality. The quality of cryptography engineering is the major deciding factor at that point and it is tricky to get right.

To determine if you should use VeraCrypt or let Comodo Backup do the encryption you need to assess the effectiveness of their cryptography engineering.

The simplicity of using the built-in encryption supplied by Comodo Backup is a significant convenience advantage. If their crypto eng is up to scratch I'd make that your choice.

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    $\begingroup$ Thanks. Beyond allowing you to select an encryption algorithm, Comodo Backup offers no details or options. I did find some additional information, which I'm adding to the original post. $\endgroup$ – Nathan Nov 15 '15 at 21:56
  • $\begingroup$ @fournines it's not terribly clear if they use sound cipher modes or IV generation when you pick AES-128. If they use PBKDF to derive the keys from the password it would be better, but it looks like they generate a key by hashing, which gives terrible entropy. You'll need to generate a strong random password to mitigate that. $\endgroup$ – Alain O'Dea Nov 15 '15 at 22:07
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    $\begingroup$ VeraCrypt allows you to move the mouse to generate entropy. Seems in this case, it would be worthwhile to take the extra time and encrypt separately from the backup process. Thanks for your help. $\endgroup$ – Nathan Nov 15 '15 at 22:13
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    $\begingroup$ @fournines I think you're confused here what "entropy" means. The entropy generated by mouse movements in VeraCrypt would be used to generate better "salts" or "initialization vectors". The entropy meant by Alain is the entropy of the password (or: how many guesses an attacker would have to make on average to bruteforce the password by trying passwords one by one). $\endgroup$ – Daan Bakker Nov 16 '15 at 3:42
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    $\begingroup$ Well, "uses SHA256" is a good start. But if it is just a single hash operation, dictionary attacks are still on the table. If you use a password or passphrase, you have to use a construction which is meant for low entropy input, such as passwords. And PBKDF, bcrypt, scrypt, etc. are such constructions. $\endgroup$ – tylo Nov 17 '15 at 15:40
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You wrote in the comments:

Thanks. Beyond allowing you to select an encryption algorithm, Comodo Backup offers no details or options. I did find some additional information, which I'm adding to the original post.

After looking at the list provided:

Mentioning XOR and DES as valid choices (even if not marked as "strong or higher") is a terrible design error. You have to expect that user's don't understand the meaning of "weak" and the empty space behind DES. But here is the translation:

  • Xor - Variable block size / weak $=$ almost equal to no encryption
  • DES $=$ can be brute forced within hours today

Additionally, implementing cryptography securely is a hard task, and should never be any non-experts. However, as a user of the program, you have no idea if they used proper crypto libraries, if they don't tell you.

In an application, where security is the main feature, I would expect such information. Throwing buzzwords (popular encryption and hash functions) around does not really imply deep knowledge of the subject. Even if they use proper encryption methods, security is so easy to get wrong: The chain breaks at the weakest link, and if they use good cryptography in the wrong way, security as a whole is still broken.

In the end, it comes down to your requirements:

  • If you need really tight security to protect crucial information, use a proper tool.
  • Don't try to create one yourself.
  • Don't trust in unsubstantiated security claims.
  • If possible and you have deep knowledge of cryptography/it security , look for detailed information and check their claims. If not, look for certification by people who do.

Especially if security is advertised with hand-wave arguments, chances are that not much effort was made there.

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