I have a hard drive which was encrypted with XTS-AES 128-bit on OS X. I know how long the password is but that's it. How long would it take to decrypt it already knowing this? I have read that in years to come when quantum computers are available it can be broken. Dont comment "never" or "6 billion year" Think outside of the box with advancing technology in years to come. I have memories on here.

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    I think as grgarside said. It can be broken without quantum computers. Is your question, should you wait until quantum computers are being made for the consumer to decrypt you hard drive?
    – markhunte
    Commented Feb 21, 2015 at 17:42
  • +1 for Q&A - sometimes one needs to be reminded of what/why on security matters, & the importance of backups &/or mnemonics for encrypted data, however harsh that reminder might appear to be.
    – Tetsujin
    Commented Feb 21, 2015 at 17:51
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    Since you want out the box. I moved this comment here. wonder if it is that important if you would consider a hypno-therapist to maybe unlock the password from you memory
    – markhunte
    Commented Feb 21, 2015 at 18:14
  • I’m voting to close this question because it is a hypothetical question about encryption and not directly related to Apple products or their use.
    – nohillside
    Commented Dec 15, 2022 at 18:11

3 Answers 3


The average 12 character password will take 6 billion years to brute-force at 100,000 passwords per second.

Allowing special characters brings this to around 150 billion years.

For more information, see Security.SE:

  • Thanks but I need a reasonable time. There must be a more reasonable time possible.
    – Drew
    Commented Feb 21, 2015 at 17:41
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    @Drew There's no point in encryption if one can brute-force it in a reasonable time.
    – grg
    Commented Feb 21, 2015 at 17:42
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    The 'reasonable time' is 6 billion years. 150 billion might try the patience of a saint :p
    – Tetsujin
    Commented Feb 21, 2015 at 17:43
  • George's answer are reasonable estimates for professional attempts. My guess is you'll not be able to get close to 100k guesses a second without serious $$ and time invested. You could get lucky though - if the third attempt worked, it would be less likely than winning many lotteries, but it could happen no matter how unlikely.
    – bmike
    Commented Feb 21, 2015 at 19:50

Dont comment "never" or "6 billion year" Think outside of the box with advancing technology in years to come.

200 years from now, it will be possible to crack in 4 minutes.

Is that the kind of answer you're looking for?


The block size is 128-bit but the key is 256 bit key."Shown below"

As such, AES-256 is medium term secure against a quantum attack, however AES-128 is broken, and AES-192 isn't looking too good. Source https://crypto.stackexchange.com/questions/6712/is-aes-256-a-post-quantum-secure-cipher-or-not

FileVault uses the user's login password as the encryption pass phrase. It uses the AES-XTS mode of AES with 128 bit blocks and a 256 bit key to encrypt the disk. Source http://training.apple.com/pdf/WP_FileVault2.pdf


This is also should be helpful.

For AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths: 128, 192 and 256 bits.
Source Advanced Encryption Standard on wikipedia.

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