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There's an answer on superuser to this question, but I'd rather have an authoritative answer from a security perspective.

Is it generally safe to host an encrypted master password file (such as that used by 1Password) on a cloud storage provider (Dropbox, iCloud, etc.)? What are the relative risks inherent in doing so, and can those additional risks be effectively mitigated?

  • I don't understand why this question is being downvoted. It's a legitimate security question. – Stephen Touset Oct 16 '16 at 7:08
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    @StephenTouset Maybe because it was already answered on SU and duplication does not create any new value. Or maybe because all questions "how safe is..." are generally frowned upon here. Or maybe because there is no question in this question, just a request for different opinions (which is why I voted for closure as opinion based). – techraf Oct 16 '16 at 8:15
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    The questioner has a reasonable point, which is that SU may not be the best place to get a security-minded answer. Wouldn't it be better to reword it to match our policies than to simply downvote and close it? – Stephen Touset Oct 16 '16 at 8:19
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    The question/answer on SU is also 5 years old. Security issues tend to change in 5 years. – MikeP Oct 17 '16 at 20:29
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Disclosure: I work for AgileBits, the makers of 1Password.

Short answer

The safety of your 1Password data on Dropbox depends on the quality of your 1Password Master Password.

Long answer

The long answer is just an explanation of the short answer and a couple of other things.

We designed 1Password under the assumption that some people would have their encrypted 1Password data stolen. Whether it is stolen from their own computers (someone walks off with a laptop) or from something like Dropbox doesn't really matter. It is possible for the data to be stolen, and this is why it is encrypted with keys that are encrypted with keys that are derived from your Master Password.

Now we make heavy use of PBKDF2 to slow down automated Master Password guessing in the event that the 1Password data is captured, but PBKDF2 and the like only present a speed bump to the attacker; it does not provide a solid barrier. So it is important you pick a good Master Password.

More than five years ago, we offered some advice on picking a good Master Password in Toward Better Master Passwords. This advice was picked up by XKCD and made famous, but it satisfies what I call the Kantian Principle of password creation advice: Password creation advice should remain good advice even if everyone follows it.

Do not reuse your Master Password. In the three known (to us) cases in which someone's 1Password data was compromised, the user used the same password that they used elsewhere for both Dropbox and for their 1Password Master Password. Don't be like them.

Beyond Dropbox

At the risk of descending into a sales pitch, I should point out that with a 1Password account, you no longer need to manage your synching through something like Dropbox. We have even designed this with Two-Secret Key Derivation (2SKD) so that even if your data is captured from our servers, an attacker would not be able to launch a password guessing attempt against that captured data. Please see our white paper (PDF) for details of how that is managed.

But as the question was specifically about 1Password data on Dropbox, let me return to that ...

OPVault v Agile Keychain

Depending on when you started using 1Password and on which platform, you may be using the Agile Keychain format on Dropbox. The Agile Keychain Format was designed nearly a decade ago and has some shortcoming for a today's world. It exposes much more "meta data" than is appropriate and it does not include any tamper detection.

So the one thing I would recommend to those synching 1Password data with something like Dropbox is that they switch their sync format to the OPVault format. OPVault encrypts far more meta data, and uses authenticated encryption to defend against a wide class of attacks that involve tampering with the data.

But with either data format, the safety of your 1Password data depends on the quality of your 1Password Master Password. Make it unique, strong, and memorable. And you may wish to write it down and keep that in a safe place because there is absolutely nothing we can do if you forget your Master Password.

With a 1Password Account, a good Master Password is still needed to protect you if data is stolen from your local machine, but 2SKD does protect you if data is stolen from us.

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Decent password managers all use modern encryption technology, usually AES-256 in an appropriate mode, which is simply not attackable directly without knowing the key. The weak point is therefore attacking the encryption key, which is derived from your master password.

If you use a weak password, storing your database on Dropbox is a bad idea (more accurately, using a weak password is a bad idea if you plan to store your database on Dropbox). Cracking tools have modules to guess millions of passwords per second for 1Password, as well as other password manager formats. The thing is, it's actually very impressive that 1Password was able to keep that number so low. A good password manager like 1Password uses technology to make guessing much slower; without it cracking tools can do hundreds of billions or even trillions per second.

So anyway if the risk is attacks on weak passwords, the mitigation is a measurably strong password. Using an 8-word diceware passphrase, current technology and cracking techniques would take billions of years to guess it.

You can mitigate the risk even further if your password manager supports incorporating extra data not kept in Dropbox, like KeePass's key files, in addition to your strong master password.

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    All these answers are helpful—I'm not sure why they were all downvoted. Perhaps someone from Dropbox didn't like them? – iconoclast Oct 17 '16 at 16:56
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In general, it is less safe to have your 1Password keychain on Dropbox, but if you take all necessary precautions, including having an excellent master password and having Dropbox locked down, it is reasonably safe. There are other methods of syncing between devices though. If you're concerned about it, perhaps use one of these other methods.

If you do choose to store your 1Password file on Dropbox, you should have an excellent password on your Dropbox account, as well as two-factor authentication enabled on Dropbox to make it more difficult to get into. From there, having a very strong master password is essential to ensuring the security of your keychain. The stronger the 1Password master password is, the harder it will be to crack in the case that your Dropbox account is compromised. As stated by Jeffrey Goldberg, 1Password does have measures in place to make bruteforcing a password more difficult, but you should still do your due diligence in choosing a strong password.

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It is safer to not store it on Dropbox. If you store it on your computer and your phone, there are two possible points of compromise. (3 if you include the connection over which you sync them.) If you add Dropbox to the list, you're bringing that to 3 (or 5+ including connections). So there must be fewer points of compromise, and thus more safety, without Dropbox.

@ciphercodes adds a useful detail in the risk that you'll mistakenly share the file.

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    Obviously hosting something on a cloud provider is intrinsically less safe than hosting it only on a machine under your own control. The interesting part is how much less safe, and whether or not that additional risk can be mitigated. Even though there's more surface area for attack, if one uses a strong master password, an attacker would need a failure in two systems — Dropbox's authorizatoin and 1Password's storage format — in order to successfully conduct an attack. – Stephen Touset Oct 17 '16 at 18:38
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Good security should not be at the expense of usability. Dropbox offers availability and backup for your data which may be what you are looking for.

If your master password uses a strong encryption, you could consider acceptable the risk of your encrypted keychain being stolen (c.f. Joeffrey's answer). I'd suggest using 2 factor auth on Dropbox to reduce that risk

  • "Good security should not be at the expense of usability"? Really? I would take the opposite approach, but either way that's beside the point. Being convenient does not change how secure it is. They are separate questions. – iconoclast Oct 18 '16 at 18:48
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Storing any sensitive file over any file hosting site is not safe.

The security of your 1password file is as good as:
1password file's encryption,
Dropbox security and
User security awareness and measures taken.

1password File: 1password file is encrypted and is not easy to decrypt but it is still possible that it can be decrypted if it gets in to hands of hackers. Hashcat does support 1password file decryption.

Dropbox Security: Dropbox is a well known known file hosting company but they have been compromised in past.

User awareness: There are chances that the user may accidentally publish or share the folder or file. If the user is using the same password on Dropbox from a not so secure website and there are chances of the hackers getting in to your Dropbox account. If the user fails to log out or looses your phone etc. then the Dropbox account is exposed.

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