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I would like to use a dropbox because it is easy and convenient. But I want to encrypt the files with the public key of the intended recipient, so he will be the only one who can access the data in the file.

I have not found an easy mechanism to encrypt the data before it is stored in the dropbox.

Is there an easy way to do so or is there aleady a service that supports my wish?

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8 Answers 8

If you are already settled on using DropBox, then your only choice at the moment is to use a 3rd party program such as PGP (or free/open GPG) to first encrypt the file and place it into your drop box. I know you said you wanted to use public/private keys, but as an alternative, you could also use 7-zip to create secure archives with AES encryption based on a pre-shared key (password).

If you have not yet decided on DropBox, you can look at similar online storage systems such as SpiderOak, Cryptoheaven, Mozy, etc. which perform client-side encryption of the files prior to uploading them into the cloud. You control the encryption key, and therefore the storage providers cannot access the data. I am not sure whether you can import existing private or public keys into those solutions or not, however.

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Thanks for your comment. I have not decided on DropBox but I would like to use a DropBox like solution. I want to share documents with other people over the internet. But I want to use personal keys for the encryption and not rely on encryption keys provided by the solution provider. I want a little program sitting on my site for the encryption (like e-mail encryption in outlook) based on the cert of the intended recipient. Because of file size e-mail is no option to use. –  Hotze de Jong Jan 2 '12 at 19:43
    
+1 for 7zip (as long as you don't forget the password...) –  nutty about natty Jun 6 at 20:07

True Crypt may suit your needs. It offers the ability to use keyfiles to encrypt your files which can then be stored in your drop box and shared. It also offers the ability to use tokens and smart cards to secure your files. This lets your key be passed in an out of band manner.

In my opinion the best feature of true crypt is the ability to create hidden volumes. This creates what the creators of true crypt call plausible deniability. This basically means that there is a second encrypted volume that appears to be comprised of nothing more than random data. This is created inside of your encrypted file using using the free space at the end of the first volume. It is also worth noting that several different encryption algorithms are available.

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Thank you for your suggestion. Creating a TrueCrypt volume and sharing the volume in a dropbox like solution might do the trick. But it still requires the other people to do something that is not familiar to them. I would like to have a transparent solution (that can also be used by people who are not technical skilled) in such a way that it cannot go wrong. –  Hotze de Jong Jan 2 '12 at 19:51

Give Wuala a shot. Data is encryted on the users device before uploaded to the cloud. It does not come with key-files but passwords. Maybe this is sufficient for you?

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I personally have this problem which I solved it myself.

I created a program which works with GPG4Win, and encrypt all my files with my PGP Key. I can also specify which folder encrypt with which user key, quite good in my opinion.

It is a 1 way sync + encrypt from my data folder to Skydrive folder (local), then Skydrive will sync to the SkyDrive Cloud. The best part is that this program does not store your PGP key, or any cloud account password.

Experience it!

Feel free to drop a visit @ http://successreality.blogspot.sg/2013/10/encrypt-sync-4-cloud.html

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Use an S3 bucket from AWS; server side you can have it encrypted and then to connect you can provision each other secure keys and use them for auditing and logging. With the use of Transmit you can add the bucket as a device in finder on OSX and treat it as a local drive which stores and pushes straight to the cloud.

http://aws.amazon.com/s3/

It's the back end of dropbox, but it's dirt cheap and you can even choose the geographical region for your data centre.

Edit; For the purpose of securing communication client side while integrating with an S3 bucket, you can use the S3 client side encryption mechanisms.

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But the point of this question is sharing it securely which implies client side encryption with a key the server doesn't know. You can use s3 as a backend behind a secure file sharing system, but it isn't secure by itself. –  CodesInChaos Oct 30 '13 at 16:35
    
Built in is a client side encryption service; docs.aws.amazon.com/AmazonS3/latest/dev/… –  Robert Smith Oct 30 '13 at 16:42
    
So basically just run your own service. This answer doesn't really help since the OP is looking for something similar to Dropbox. Having to develop a Dropbox clone first is not really what he was looking for I think. –  Luc Oct 30 '13 at 17:38

I created a small tool to do this. http://www.itsencrypted.com It uses the user's public key to encrypt a key file, which unlocks the encrypted file which is also in your Dropbox. Then later he'll use the program to download it directly and unencrypt it.

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Another good solution is Boxcryptor. It encrypts all your data before they are send to Dropbox (or other providers). Boxcryptor also allows you to share your data in a confidential way. Therefore it makes a public/private key pair for each user. When you want to share a file with a friend, Boxcryptor downloads the public key of your friend, encrypts the file and your friend receives and decrypts the file.

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A bit late to the game, but try Turtl. Uses client-side encryption and allows easy sharing/collaboration for both files and notes. Disclosure: I'm the founder.

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Are you affiliated with the linked software in any way? If so, please disclose your affiliation. –  Deer Hunter Mar 7 at 10:46

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