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I know client side encryption is generally not seen as ideal. However, I can't imagine how server side encryption can ever give the user full peace of mind.

If data is encrypted on the client and the server only receives encrypted data, then it is impossible for the server owner, even under pressure from a government, to tamper with the data or provide a backdoor to it.

However, server side, the server owner could be under pressure from the government to funnel certain data before it enters encryption to a government backdoor.

Thus, if you were trying to build a company where even if the government forced you at gun point to give up the data of a certain user, wouldn't client side encryption provide you, the server owner, with better protection from such an ultimatum?

closed as off-topic by Xander, Arminius, techraf, Steffen Ullrich, Dmitry Grigoryev Nov 17 '16 at 11:11

  • This question does not appear to be about Information security within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

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    This question appears to be off-topic because it is requesting legal advice, which not only may vary from jurisdiction to jurisdiction but also from case to case, and so should be obtained from a qualified legal practitioner in the appropriate jurisdiction rather than from the Internet where the well-meaning and logical opinions you receive on the matter may leave you more ill-advised than if you hadn't asked at all. – Xander Nov 17 '16 at 0:02
  • It's not legal advice. It's: how to protect data from snooping eyes. aka "information security". – Snowman Nov 17 '16 at 0:05
  • It is legal advice. If you think you can defeat warrants and nation state level adversaries with naive technical measures, you're sadly mistaken. – Xander Nov 17 '16 at 0:08
  • I deleted my answer because I initially misread the question. It's not really answerable because nobody could tell for sure how a government would react. Likely, they would still ask you to hand over your servers to see if they can find something. – Arminius Nov 17 '16 at 0:33
  • @Xander ok so you're saying neither client side or server side encryption can ultimately help you against a government ultimatum. That's an answer. – Snowman Nov 17 '16 at 1:55
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I know client side encryption is generally not seen as ideal.

I don't think that's true; you may be mixing up a few different things.

One of the canonical rules in secure software design is to never trust the user. This means that any time you do, say, validation that a form field is in the correct format, you must do that on the server, or else an attacker can feed your application an attack payload. This holds true to certain forms of cryptography as well, as long as it's something where your application will interact with the resultant data.

What you're talking about here is end-to-end encryption. In these situations, the encrypted data is only ever dealt with in the server-side application as a binary blob. This is only useful in a few situations, like cloud storage and messaging apps, and you give up the ability to provide features many users want, like sophisticated search.

So to answer your question,

Thus, if you were trying to build a company where even if the government forced you at gun point to give up the data of a certain user, wouldn't client side encryption provide you, the server owner, with better protection from such an ultimatum?

Yes, end-to-end encryption does.

There are further things to consider, though. Is the client application closed source? Then how can the user verify that you aren't sending the data off unencrypted to your (or the government's) servers? Is the client application installed through an app store? How can the user verify that you haven't pushed a new version of the app that makes significant changes from the one they audited? Is the client application installed as a binary? How can the user verify that the binary you're providing comes from the unmodified source that they've read? The recent Apple FBI controversy dealt with some of these issues.

Also related is the subject of forward secrecy, in which a key that's been handed over to the government doesn't allow them to decrypt past conversations.

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