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Since I am new to encryption and have recently been losing stuff, I decided to start a file that contains some passwords for online accounts and whatnot, encrypt it, back it up (and keep a single copy on Google Drive....cloud storage seems insecure to me.)

I was wondering about using GPG though.

Is the default algorithm, CAST5, sufficient? gpg -c file uses it

Is there any chance that my file could be broken by Google? It uses a long password that seems secure.

Should I add extra information throughout to act as "additional entropy"? Maybe dd if=/dev/random >> file

And the most important question...is GPG even right for this job-encrypting basic text files. Is there a better, mroe secure option, or a faster option?

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  • 5
    Google Drive IS cloud storage ...
    – schroeder
    Jul 8, 2014 at 23:13
  • Why not a password manager? KeePass, LastPass, Password1, etc.?
    – schroeder
    Jul 8, 2014 at 23:14
  • @schroeder I don't know...what if I forget my master password to one of those? And yes, I know GD is cloud, but I still feel weird. They suddenly have all of my data, but they probably did before anyways.
    – user50625
    Jul 8, 2014 at 23:18
  • What happens if you lose your password to the GPG-encrypted file?
    – schroeder
    Jul 8, 2014 at 23:18
  • A password manager also has the ability to use 2FA, which is a huge boost to the security of the data.
    – schroeder
    Jul 8, 2014 at 23:20

1 Answer 1

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CAST-5 aka CAST-128 is a fine choice of algorithm. It probably hasn't had as much cryptanalysis as, say, AES, but there are no significant publicly-known weaknesses in the algorithm. It's a 128-bit cipher, which is computationally infeasible to brute force, and so all of the security depends on the security of your passphrase. GPG performs a technique known as "key stretching" (see the s2k options) to make it harder to brute force passphrases as well.

GPG is a great tool for encrypting text files -- that's basically what it's designed to do. (Encrypt arbitrary blocks of data.) You can use a password manager if you prefer to have your data structured/managed for you, or select something that plugs in to your browser.

Should I add extra information throughout to act as "additional entropy"? Maybe dd if=/dev/random >> file

This won't do any good. Modern crypto algorithms are not dependent upon any entropy present in the plaintext, but only in the key being used. A known-plaintext attack on a cipher would render it dead from a cryptography point-of-view, so this should not be your concern.

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  • Alright, so suing GPG is fine, and the default of CAST-128 is also fine. I assume it wouldn't even compare to AES-256, but then I'd have to actually learn how to use GPG because trying that it asks for UIDs and whatnot
    – user50625
    Jul 8, 2014 at 23:55
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    gpg --cipher-algo AES256 if you want it.
    – David
    Jul 8, 2014 at 23:59
  • Will I have to remember that when I go to decrypt it or will GPG automatically handle that?
    – user50625
    Jul 9, 2014 at 0:30
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    GPG adds a header to the file that includes the algorithm used, so it will know which algorithm to use when decrypting.
    – David
    Jul 9, 2014 at 3:38
  • I think choosing a good password is more important than the algorithm. If the password was a simple dictionary word, then no cipher algo can save
    – balki
    Dec 17, 2014 at 18:46

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