Jump to content


 


Register a free account to unlock additional features at BleepingComputer.com
Welcome to BleepingComputer, a free community where people like yourself come together to discuss and learn how to use their computers. Using the site is easy and fun. As a guest, you can browse and view the various discussions in the forums, but can not create a new topic or reply to an existing one unless you are logged in. Other benefits of registering an account are subscribing to topics and forums, creating a blog, and having no ads shown anywhere on the site.


Click here to Register a free account now! or read our Welcome Guide to learn how to use this site.

Photo

How to encrypt files to be shared on Dropbox?


  • Please log in to reply
31 replies to this topic

#1 Cynthia Moore

Cynthia Moore

  • Members
  • 300 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:04:57 AM

Posted 08 May 2015 - 01:33 PM

I frequently need to share files on Dropbox. These files often contain personal and private information. I would like to encrypt the files, but I do not want to burden the recipients by requiring that they install special software to be able to decrypt them.

 

My solution to date has been to put all of the files into an encrypted ZIP file. This works. Most people have an unzip program. The downside is that it is a hassle to add or remove files. The entire zip file, which can be quite large, must be replaced.

 

Is there a tool I can use to encrypt individual files that can easily be decrypted by anyone (on any system) who has the pass code?

 

Thanks


Running Win 10 & Office 365.


BC AdBot (Login to Remove)

 


#2 RolandJS

RolandJS

  • Members
  • 4,533 posts
  • OFFLINE
  •  
  • Gender:Male
  • Location:Austin TX metro area
  • Local time:06:57 AM

Posted 08 May 2015 - 01:56 PM

Elsewhere, another tech indicated: one cannot encrpyt a file on C, send to Dropbox, with said file staying encrypted.  Somehow, the encryption is lost during the transfer [copy operation]. I've never used either encryption or dropbox, so I do not know if that tech's info applies to what you're wanting to do.


Edited by RolandJS, 09 May 2015 - 10:16 AM.

"Take care of thy backups and thy restores shall take care of thee."  -- Ben Franklin revisited.

http://collegecafe.fr.yuku.com/forums/45/Computer-Technologies/

Backup, backup, backup! -- Lady Fitzgerald (w7forums)

Clone or Image often! Backup... -- RockE (WSL)


#3 rp88

rp88

  • Members
  • 3,060 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:11:57 AM

Posted 08 May 2015 - 02:02 PM

I would use 7z, There is a download link for it on bleepingcomputer's downloads section, but it would need the other person to run 7z as well. Fortunately 7z is a pretty common program, sometimes it even comes bundled on computers which are new, but it isn't a standard built in function of most operating systems (windows cannot deal with 7z files itself, some linux types might be able to) so for those who haven't installed 7z themselves for some reason in the past they would need to install it before they could opne the encrypted files. One good thing is that being available on this site there is a safe download link you can provide to those people who don't have 7z already. 7z, atleast the version I use (same version as is available at http://www.bleepingcomputer.com/download/7-zip-for-windows/ ), can also make self-extracting archives. But there are issues with these. Self-extracting archives are exe files, and if a user is cautious about installing 7z you can be sure they won't feel safe in running an exe file you just sent them.


7z won't free you of the compressing/extracting requirement, it is just like zip files for this, but a bit faster. 7z does however offer more powerful encryption (the type used as standard on zip files is apparently not that strong, whereas 7z uses AES 256) and will allow anyone to encrypt and decrypt files. On the latest versions of windows the built-in zip file processing systems let anyone open zip files if they have the password, but only users of particular (pro and enterprise I think) windows versions can make encrypted archives. With 7z anyone with it installed can make encrypted archives, anyone with 7z installed can open them with the password.

7z archives (especially if you first put the secret files into an ordinary zip file, then put this zip file into an encrypted 7z archive) also give greater protection to information such as the file names, there is an option during encryption to encrypt these so they cannot be seen without entering the password. If you put the secret files in a zip file and then the zip file into a 7z then eavesdroppers couldn't see the individual file sizes either (they might be able to see that the 7z archive held a zip file called secret-files.zip which was a particular number of megabytes in size, but they wouldn't know whether the zip file had one big file, many little ones or a mixture, and they wouldn't know the names of the files within it).

As far as I am aware the only ways of encrypting files without putting them into archives are:
1 )special file formats that only open with specialised programs, the receiver would need the special program installed and you might onyl be able to pass text through rather than files such as images, audio, pdf, video, word documents.
2 )disk encryption and file vaults, things like truecrypt and bitlocker, these sort of things are not usually easily copied from place to place as they are closely connected with the drive on whcih the encrypted files are saved.
3 )manual encryption of file contents, basically encoding your message by hand then typing the ciphertext into a document, very slow and cumbersome to encrypt and de-crypt, not very secure compared to the sorts of ciphers used in other methods.

For encrypted archives RolandJS's concern will not apply, they maintain there encryption wherever they are copied and sent to, the encryption is part of the file, it doesn't get messed up by copying. For types 1 ) and 2 ) discussed above, his concerns can and often will apply. They also likely apply to types of encryption software sometimes bundled on USB sticks when you buy them. His concerns also likely apply for some types of encrypting done by built in tools into windows, older versions atleast. They should not apply to encryption of zip files by window's internal tools, they certainly don't apply to encrytion by 7z.


P.S. How are you telling the recipient the password they need to open the file? Have you pre-agreed it, phoned them to tell them, agreed a common source like "the first 3 words on the second page of a particular newspaper we both read, all written backwards"?

Edited by rp88, 08 May 2015 - 02:07 PM.

Back on this site, for a while anyway, been so busy the last year.

My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB

#4 Cynthia Moore

Cynthia Moore
  • Topic Starter

  • Members
  • 300 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:04:57 AM

Posted 08 May 2015 - 02:13 PM

Elsewhere, another tech indicated: one cannot encrpyt a file on C, send to Dropbox, with said file staying  encrypted.  Somehow, the encryption is lost during the transfer [copy operation]. I've never used either encryption or dropbox, so I do not know if that tech's info applies to what you're wanting to do.

As I said above, I upload encrypted ZIP files all the time. None of them have ever "lost" their encryption.

 

If you think about it, this makes no sense. If an encrypted file could be decrypted simply by uploading it to Dropbox, encryption wouldn't be worth much, would it?


Running Win 10 & Office 365.


#5 Animal

Animal

    Bleepin' Animinion


  • Site Admin
  • 35,758 posts
  • OFFLINE
  •  
  • Gender:Male
  • Location:Where You Least Expect Me To Be
  • Local time:04:57 AM

Posted 08 May 2015 - 02:58 PM

Have you seen this?

https://www.boxcryptor.com/en/dropbox

Never used it or know anyone who uses this particular application. But looks interesting and might fit your needs.

The Internet is so big, so powerful and pointless that for some people it is a complete substitute for life.
Andrew Brown (1938-1994)


A learning experience is one of those things that say, "You know that thing you just did? Don't do that." Douglas Adams (1952-2001)


"Imagination is more important than knowledge. Knowledge is limited. Imagination circles the world." Albert Einstein (1879-1955)


Follow BleepingComputer on: Facebook | Twitter | Google+

#6 O.T.T.

O.T.T.

  • Members
  • 172 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:12:57 PM

Posted 09 May 2015 - 05:02 AM

I use CryptSync (freeware) for all my Cloud computing. It works with 7z and with a 2 folder-system.

There's a bit of a learning curve but it works for me !

 

OTT


Please ask Google why some of my links don't work anymore !


#7 RolandJS

RolandJS

  • Members
  • 4,533 posts
  • OFFLINE
  •  
  • Gender:Male
  • Location:Austin TX metro area
  • Local time:06:57 AM

Posted 09 May 2015 - 10:22 AM

Guys, I have no worries or concerns  :)   I was simply passing on what another tech elsewhere said about sending single encripted files such as TXTs, DOCs, etc., [not using any zip program] up into Dropbox.  Elsewhere that OP mentioned any single file sent to Dropbox became readable in a viewer or MS Explorer PreView Panel, even though encrypted.  Again, I have no worries or concerns; I use 7zip, making passworded and unpassworded zip files all the time.  :)


"Take care of thy backups and thy restores shall take care of thee."  -- Ben Franklin revisited.

http://collegecafe.fr.yuku.com/forums/45/Computer-Technologies/

Backup, backup, backup! -- Lady Fitzgerald (w7forums)

Clone or Image often! Backup... -- RockE (WSL)


#8 Cynthia Moore

Cynthia Moore
  • Topic Starter

  • Members
  • 300 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:04:57 AM

Posted 09 May 2015 - 11:23 AM

Guys, I have no worries or concerns   :)   I was simply passing on what another tech elsewhere said about sending single encripted files such as TXTs, DOCs, etc., [not using any zip program] up into Dropbox.  Elsewhere that OP mentioned any single file sent to Dropbox became readable in a viewer or MS Explorer PreView Panel, even though encrypted.  Again, I have no worries or concerns; I use 7zip, making passworded and unpassworded zip files all the time.   :)

I would be very interested to know if this is true and, if so, how it works. Maybe you can invite him to come here and enlighted us (me).


Running Win 10 & Office 365.


#9 RolandJS

RolandJS

  • Members
  • 4,533 posts
  • OFFLINE
  •  
  • Gender:Male
  • Location:Austin TX metro area
  • Local time:06:57 AM

Posted 09 May 2015 - 11:40 AM

Cynthia, if I find that thread -- I'll definitely either post the URL or invite that tech over here  :)


"Take care of thy backups and thy restores shall take care of thee."  -- Ben Franklin revisited.

http://collegecafe.fr.yuku.com/forums/45/Computer-Technologies/

Backup, backup, backup! -- Lady Fitzgerald (w7forums)

Clone or Image often! Backup... -- RockE (WSL)


#10 rp88

rp88

  • Members
  • 3,060 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:11:57 AM

Posted 09 May 2015 - 01:10 PM

Regarding " I was simply passing on what another tech elsewhere said about sending single encripted files such as TXTs, DOCs, etc"

And in those examples I think that tech is right, there are certainly some instances where you encrypt a file in windows and the encryption doesn't apply to copies made of it. The types of encryption other than encrypted archives are:

1.Disk encryption methods: these are designed to make it very hard, potentially impossible, for an attacker without your password to gain any sort of access to your system. But once you are logged in this sort of encryption has already been passed (at point of login) so you can copy to external drives or upload to the internet and the copy won't be encoded.

2.Special types of encryption within files: pdfs and word documents can be encrypted, but sometimes these types of encryptions can be bypassed just by opening the file in a different program. Other times these sort of encryptions will make the file a load of garbled junk if opened in a program other than the one which encrypted it. This sort of encryption will usually survive the copying of files to external discs or upload to websites but is either insecure (if it can be bypassed by opening in other programs) or inconvenient (if opening in other programs makes the encrypted file appear as garbled junk then the receiver needs to open it with excatly the program, sometimes excatly the same version of the same program, as you encrypted it with).

3.Ways of hiding things on a computer: there are ways of hiding files on a computer which are not particularly useful against anyone determeined to find them, these involve storing them in unusual ways so they are sort of "connected" to other files and opening those other files by command line methods with a password as an attribute will let the hidden files be opened. These methods are often described in articles and tutorials as fun tricks to know for keeping things slightly hidden from casual observers, they aren't secure against even a normal computer users if that user knows some basic counter-tricks. This sort of "encryption" will not work for copying as it "encrypts" things by hiding the file, the copying the cover file will not bring the hidden one with it, copying the hidden file will result in a normal unhidden copy.

So encrypted archives are probably your best bet for emailing private files to people, atleast once they've downloaded 7z the first time they'll be able to open all subsequent 7z files you send them and they'll have a program which can open rar and other compressed file formats as well (7z can't create rar files but it can read them, it can create and read zip files, there are a long list of other formats it can read, and a somewhat shorter list of other formats it can create). There is no way for cloud storage services to read your private 7z files unless they support the format (google drive atleast just considers it unrecognised and willing stores it but can't preview it) AND have the password. You could put a load of private information in a 7z file, encyrypt it with a strong password, upload that file to a public download page, write that file to USB sticks and leave them lying on the streets, copy that file onto a cd-rw or dvd and mail it any address in the world and theoretically no-one downloading it from that page, no-one picking up a USB stick and no-one getting a disc in the post would be able to know anything mroe than the file size and the fact it held a zip file called my_secrets_just_out_of_your_reach.zip. The sort of encryption 7z uses is designed so that anyone can know anything about the 7z program (it is open source after all), about the encryption algorithms used and about the way the format works, and they still can't read your files without your password.

Regarding "any single file sent to Dropbox became readable in a viewer or MS Explorer PreView Panel"
For files encrypted with methods like (2.) this may apply, for methods of types (1.) and (3.) it certainly does apply. In my experience with encrypted 7z files in google drive (that is google drive in the browser, not the program based way of using it) google doesn't even recognise the format, it can't preview non-encrypted ones so it certainly can't preview encrypted ones. And if google does at some point support previewing for 7z (as they currently do for zip) they should not be able to preview the encrypted ones beyond what one can see when trying to open them in 7z without supplying a password.

For encrypted 7z files to be opened the attacker either needs to make some extraordinary discoveries in mathematics (the p=?=np problem, mathods of quick and efficinet factorisation and formaulae for predicting positions of prime numbers) or develop an effective quantum computer (the current best one can just about prove that 5 and 3 are rime factors of 15, on a good day) or have a huge array of supercomputers dedicated to brute-forcing each encrypted 7z file they want to crack, one at a time.

Edited by rp88, 09 May 2015 - 01:11 PM.

Back on this site, for a while anyway, been so busy the last year.

My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB

#11 VB30

VB30

  • Members
  • 24 posts
  • OFFLINE
  •  
  • Local time:09:57 PM

Posted 10 May 2015 - 09:22 AM

Hi Cynthia,

 

Not sure if this would suit your needs as i have not used the program.

 

http://www.axantum.com/AxCrypt/

 

 

 

AxCrypt is used to share and work with stored documents, and e-mail attachments, in a secure manner.

If your documents reside on a document sharing service, intranet or file server AxCrypt is especially well suited and will usually seamlessly integrate, and make sharing and storing sensitive data as easy as not protecting it.

To send secure e-mail, agree on a pass phrase and ensure that all parties have AxCrypt, then send your encrypted files as regular attachments. With the pass phrase cache and the double-click edit feature even many turns over e-mail is as easy as without encryption.

 

 

 

http://www.axantum.com/AxCrypt/Tips.html

 

If this suit's your needs, note the program does have "Open Candy" in the installer. If you do not want the "Extras" installed, see link below :

 

https://www.axantum.com/AxCrypt/Freeware.html

 

Regards.



#12 O.T.T.

O.T.T.

  • Members
  • 172 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:12:57 PM

Posted 10 May 2015 - 01:50 PM

I use AxCrypt and can recommend it !

Very handy for sensitive data on USB drives...

 

You need the software to decrypt unless you encrypt to exe but then you have to send exe-files to your Dropbox-friends which isn't always desirable.

 

OTT


Please ask Google why some of my links don't work anymore !


#13 RolandJS

RolandJS

  • Members
  • 4,533 posts
  • OFFLINE
  •  
  • Gender:Male
  • Location:Austin TX metro area
  • Local time:06:57 AM

Posted 11 May 2015 - 09:32 AM

rp88, thanks for the information!  Now, I understand much better!

Encryption with strong passwords is a really good way to go.


Edited by RolandJS, 11 May 2015 - 09:32 AM.

"Take care of thy backups and thy restores shall take care of thee."  -- Ben Franklin revisited.

http://collegecafe.fr.yuku.com/forums/45/Computer-Technologies/

Backup, backup, backup! -- Lady Fitzgerald (w7forums)

Clone or Image often! Backup... -- RockE (WSL)


#14 rp88

rp88

  • Members
  • 3,060 posts
  • OFFLINE
  •  
  • Gender:Not Telling
  • Local time:11:57 AM

Posted 11 May 2015 - 12:40 PM

I would suspect axcrypt and 7z's encryption both work along very similar lines. An archive like files to hold the private files inside it. Which is more secure, I wouldn't know how to tell, they are probably pretty close.
Back on this site, for a while anyway, been so busy the last year.

My systems:2 laptops, intel i3 processors, windows 8.1 installed on the hard-drive and linux mint 17.3 MATE installed to USB

#15 MDD1963

MDD1963

  • Members
  • 699 posts
  • OFFLINE
  •  
  • Local time:08:57 PM

Posted 03 October 2015 - 08:21 PM

Glary Utilities, fairly common and free for personal use, also has a built in encryption tool, an option for which, includes building auto-self-decrypting.exe file; user at other end enters super-secure PW such as '123456' (6 character password required)...presto....file(s) created/decrypted!

 

Edit: Tested with Dropbox, which most certainly does not display a preview of files so-encrypted...


Edited by MDD1963, 03 October 2015 - 11:50 PM.

Asus Z270A Prime/7700K/32 GB DDR4-3200/GTX1060





0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users