How to securely store sensitive information?

Question

I tried finding answers on my own before submitting this question, but I failed.

I have banking information which I would like to securely share with my wife. For some reasons she can't just go to a bank and access those accounts.

So I am thinking to write up a document which will contain all of the necessary information.

I need a way to store it securely somewhere accessible. Preferably in the cloud. Of course I wouldn't want to store it just in plain text.

The only way I can think of is putting the document in the password protected ZIP file.

Answer 1

As soon as I hear store sensitive information, I think of password managers. That is what they are made for, and some of them do it very nicely. For example the excellent Keepass allows to store additional informations associated with a particurlar account. For example, you could create a dummy account to store a Visa card number, its PIN, validity date and 3 digit key.

You can use only local storage and synchronize different databases provided they can be visible from one machine. For example it is trivial to synchronize a desktop or laptop, a tablet and a smartphone. Synchronization is indeed one of the nicest features of Keepass.

You can also have the database somewhere in the cloud, and use a random file of several kbytes as a key that you securely store on each device where you want to use it. You can even combine that key file and a password for higher security (something you have and something you know).

The only drawback is that whatever the key is, it must be the same for all devices or users if you want to share the sensitive information. And as we all know a secret that is shared between more than two persons/devices is no longer a secret. But anyway, it would not be worse than an encrypted zip file, and the key file would even add some security because it will resist by design to dictionary attacks, and even brute force will be hard to use because the entropy of the key file is high.

Answer 2

For that situation you can use GPG Encryption + Stenography

Simple example with a picture of your preferred cat:

1. Encrypt the information file.txt gpg -c file (will create file.gpg)

2. Put the file in a picture and secure with another password steghide embed -cf cat.jpg -ef file.gpg

Share that with your wife where you wish from social network to Google drive, she will just have to extract the data:

1. Extratct the file.gpg from the picture with: steghide extract -sf cat.jpg

2. Make the file readable gpg file.gpg

Done.

Answer 3

As for myself, I use Cryptomator to encrypt some of my Google Drive stuff on the cloud. This app even encrypts the filenames (but not the timestamps) and also takes care of the Windows 256-byte path length limit.

Answer 4

Using something like gpg would be more secure than just a password-protected file, because passwords can be brute-forced but PGP/GPG private keys cannot. The problem is that this requires having your key handy when you need to decrypt the file. It also requires having an OpenPGP client to use that key. Such clients are pretty commonplace - gpg is a free and open-source one available for multiple platforms - but a random library computer or whatever probably won't have one.

If you do use password-protected ZIP, make sure it's the newer version of Zip encryption; the original one is weak and very easily broken. Of course, not all Zip handlers support the new version. I use 7-Zip personally (on Windows; there are other options for other platforms), and it works quite well, but again not all computers will have it.

It's unclear why you need to store this information online, or how you plan to access it. With more information we could offer more suggestions.

Answer 5

Open two GMail accounts and store the banking information in one, the bank information on the other, as messages sent to the accounts themselves.

E.g.

From: john.doe@gmail.com
To  : john.doe@gmail.com
Subj: Account Alpha

user foo
pass bar

From: zeke.ruesch@gmail.com
To  : zeke.ruesch@gmail.com
Subj: Account Alpha

First Merchant Bank, https://firstmerchantba.nk/login

That way:

• an attacker would need to guess both account names (you won't use your own name, also for convenience, since these accounts will be used for nothing else - you'll have perhaps hubbyandwifeflowers and hubbyandwifebees), and both passwords.
• anyone getting a peek at any one of the two accounts (but not both, of course) would find himself unable to use the information,
• you can access the accounts from anywhere, provided there's a connection and GMail is up.
• the pages being accessed via HTTPS, they won't be stored on the local PC, and they won't be intercepted in transit.

All that remains is making sure the PC you're using is not laden with spyware and keyloggers, and is not perhaps connected to a rogue AP performing MitM. So if you're traveling in Lower Crookia and checked in a hotel, and the PC says something fuzzy about the security certificates, please remember not to log in.

On the security of encrypted ZIP documents

Probably we would need to agree on some use case scenarios. The fact that secure key storages (with cloud backups) are famously available for most smartphones - I myself use SplashID - and yet we're debating encrypting ZIPs makes me think that two important requirements have to be: - accessibility from anywhere, i.e. relying on third-party hardware - possibility of flexible storage, i.e. not simply user/password pairs, possibly not even the multiple fields of SplashID.

In this scenario, an encrypted ZIP file is by no means secure, and possibly not even available. The PC being used needs a ZIP compatible software installed with password support, and the password must be entered through the keyboard, making it exactly as vulnerable to keyloggers as any other method.

Moreover, the text file will have to be read once decrypted. On most systems this means not only that the file will be available in plain text on the system for as long as it's being read (which does not happen for HTML pages on HTTPS sites, for example), but that parts of the text, and possibly the text in its entirety, will be still available for an unknown period of time in the memory swap file and/or disk temporary areas and/or or filesystem slack space. Depending on what the text editor actually is, a backup of the unencrypted file might be left lying on the system with the user none the wiser.

Answer 6

If you are up to using an online service, do you not mind the service provider to technically be able to read your data? If so, use any major web-based online notes service that utilizes HTTPS (for example, Evernote) and share the account username/password with your wife in some secure way.

You could also use those online services to share encrypted or password-protected files (e.g. ZIP as you suggested), but bear in mind that in that case your wife would need to download the file on her computer and unencrypt (which would compromise the data if her computer is hacked) — as opposed to only seeing the data in the browser over HTTPS while the window is open.

Answer 7

Standard passworded document (which covers the .zip part explained above since docs are actually .zips so it is pretty much useless putting the document in the password protected ZIP file) inside an encrypted container like the ones TrueCrypt can make.

That way, you have a file that is the container and it can hold any brute force attacks as long as the password is good enough, and then you have the password of the document itself as secondary safety.