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I need to come up with a simple way for people within the company to send out arbitrary sensitive information to arbitrary recipients. There is an equal chance that the sender and recipient will be using a MAC or a Windows machine. Assume the sender and the recipient frequently need to share sensitive information, are not technically savvy and are impatient, meaning that anything which is considered to be too difficult to understand or takes more than a couple of steps are not going to be used (and will not be enforceable).

I have found this tool which appears to solve most of my concerns: onetimesecret.com.

It basically allows some text to be entered and then generates a self destructing link which can be shared with other recipients by email. The main concern is that it's hosted by an external organisation and that it only allows transfer of text. I will get around these issues by building our own version which includes a file upload facility and will host on our own servers.

Obviously this is not a silver bullet by any means but it appears to minimise some of the risks of sending out sensitive information via email. My only concern remaining is that it potentially makes sensitive information available over a public facing link which would otherwise only be available if an email account was breached. On the other hand, that link should in theory only be accessible if somebody already had access to the email containing the link. Due to the complexity of the links it doesn't appear to be feasible to brute force them.

So if I use a solution like this and send out the links via email, am I somehow making the file more likely to be able to be accessed than if it were included in the email alone? I cant think of any way, other than by accessing the email containing the link or by brute force, that the information could be breached.

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    If you are worried about unauthorized people reading your email, why are you not worried about them reading the link? – Anders May 23 '16 at 12:46
  • The link only works once and expires within 7 days so this information would be less vulnerable than if it was included in the email directly. I realise the link could also be stolen within the space of time it takes for the intended recipient to access it but I'm looking to minimise risks not eliminate them completely. – rdans May 23 '16 at 12:48
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    Don't write something yourself, go with an existing service software bundle. – Neil Smithline May 23 '16 at 14:16
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I think that onetimesecret.com it's a very useful service, and it fits your needs. Of course, you should share the onetimesecret password by a different channel in order to increase the security and avoid the case of compromising the sensitive information if someone has access to the email account. I have dealt with these situations before and, depending on the context, I have used several tools (and also a combination of them):

  • You can use a cloud storage (like dropbox or google drive), to store a 7zip protected file with the sensitive information.
  • FTP server inside your company (You should read about Pure-ftpd in *nix)

I agree with Philipp, encrypting Emails is always the most secure alternative. But it is not always easy to implement this.

An easy way to address your concern and perform encryption, it is by creating an email account in Hushmail.com. The service allows you to set a password at the moment of sending the email (it is even easier than opening onetimesecret). But remember, you must always share the encryption key by a different channel.

  • Thanks for the contribution. Regarding the password protected zip files, we have often used this approach for sharing sensitive files however it seems to have been too difficult for our MAC users (not a mac user myself but I understand it requires use of the command line to achieve). – rdans May 23 '16 at 14:07
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    You're welcome rdans! How about The Unarchiver or izip ?. They are both free and support password protect. – Nick C. May 23 '16 at 14:24
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There already is a solution for encrypting email: It's called PGP and there are plugins available for most email programs on most operating systems. Its main problem in the real world is that you need the public key of anyone you are going to send an email to, but when you are using it internally you can fix that by setting up a keyserver on your company network which manages the keys of all employees.

Some email readers also have proprietary solutions for email encryption (Outlook, for example). You might want to check what the software you are already using provides out-of-the-box.

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    This doesn't appear to be a solution for me as its not just internal emails. In most cases it will be an internal employee emailing somebody from outside the organisation. Asking all of the potential recipients to install or set something up on their end before we email them is not a realistic proposal for my scenario. Even if it were feasible it doesn't do anything about the risks of people forwarding or cc-ing people on emails who should not have received the emails, or hackers gaining access to somebody's email account username/password (as has happened recently). – rdans May 23 '16 at 13:02
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Where I work we have a solution that will automatically detect sensitive information and replace the content with a link to a secured server. The company that sells this makes a business out of it so this isn't a crazy idea. As long as you make the links impossible to guess (long crypto-secure random strings.) The solution we use actually requires the users to authenticate so that adds another layer of protection.

As Philip mentioned, PGP and other email encryption solutions exist but if you are dealing with users outside your organization, it's probably not feasible to get them set up with what you need. This kind of solution is much easier to implement. You might want to consider purchasing one instead of rolling your own.

  • Thank you. Could you provide the name of the software your company uses to do this? – rdans May 23 '16 at 13:50
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    I fear I will run afoul of the "no product recommendations" rule of this site and I really can't vouch for it's quality. If you google for 'email encryption service' you should find it and not necessarily in the paid ads. – JimmyJames May 23 '16 at 16:47

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