I'm trying to encrypt my Samsung Galaxy S5 (AT&T) and it only allows me to use a 16-character passphrase for my encryption key.

Is there a way to bypass this or change the encryption key to something longer? This is really annoying at best and is a bad security practice to limit the size of the passphrase.

(Android internally uses the Linux dm-crypt method for encrypting the disk, which doesn't mention such password-length restrictions, and I've used it in the past with very long passphrases.)

  • Are you aware that the encryption password is also your unlock password? Therefore you have to enter it every time your phone is locked. Bad design by Google IMHO. – Robert Apr 25 '14 at 13:08
  • Oh, so this is an Android thing and not a strange Samsung invention. This really needs to be fixed. Disk-encryption and screen unlock are two different security models and should be allowed to have different passwords. – Naftuli Kay Apr 25 '14 at 17:58
  • If you have root access you can change the dm-crypt password without changing you unlock pin/password. – Robert Apr 25 '14 at 21:57

It is a poor password policy, however you should rest assured that a strong 16-digit password is sufficient to protect from brute force. As demonstrated by GRC, an exhaustive brute force attack would take 10 billion years using a massive cracking array: https://www.grc.com/haystack.htm

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