Most cloud storage services claim they "take every precaution" to keep your data secure. For example, most use encryption to make sure your files are secure in transit. They "have internal policies and controls" to ensure that employees don't access your files. But things do go horribly wrong.
For many cloud-storage users, privacy and robust encryption are top priorities. It is essential for data and documents to be encrypted before leaving their device, and it is essential that no other entities have their encryption key or any other way to gain clear-text access to their files.
On-the-fly encryption is the the most convenient way to protect your files in transit and in the cloud. That's where client-side products like SpiderOak, Tresorit, Sync and Cryptomator come in. Client-side on-the-fly encryption assures that your files never leave your computer in an unencrypted state. And your encryption key should never leave your computer.
Once it is properly set up, good client-side, on-the-fly encryption applications require no direct action by users. They and their client-side processes have fast, direct access to unencrypted files. But encryption adds complexity (things do go horribly wrong), and local backups are still important.
See also Encryption Methods at the end of this article.
Provides client-side encryption, automatic backup and sync with storage space.
Platforms/Download: [field_blackberry_download] | iOS | Linux | Mac OS | Web App | Windows (Desktop) |
Version reviewed: 4.8.4
|Our Rating: 4/5
Provides sync, sharing, 5 GB of free storage and software to sync files with the encrypted cloud storage.
Platforms/Download: [field_blackberry_download] | iOS | Mac OS | Web App | Windows (Desktop) |
Version reviewed: 1.1.7
|Our Rating: 4/5
Free and open-source software provides transparent (on-the-fly), client-side encryption for cloud storage.
Platforms/Download: [field_blackberry_download] | iOS | Linux | Mac OS | Windows (Desktop) |
Version reviewed: 1.0.3
|Our Rating: 4/5
Provides on-the-fly encryption giving you transparent access and quick sync for encrypted files.
Platforms/Download: [field_blackberry_download] | Blackberry | iOS | Mac OS | Windows (App) | Windows (Desktop) |
Version reviewed: 1.3.2
|Our Rating: 2.5/5
Provides seamless sync via the cloud, encrypted links for sharing and secure collaboration.
Platforms/Download: [field_blackberry_download] | Blackberry | iOS | Linux | Mac OS | Windows (Desktop) |
Version reviewed: 3.0
|Our Rating: 2/5
Cautionary Notes on Encryption
- Recent revelations about NSA crippling, or hacking encryption software are sobering if you store or transfer sensitive data via the internet. I would not suggest that it is prudent to trust any of the products listed here to protect your information from government agents or nation states, or determined cyber criminals.
- It still seems reasonable at this point to trust these products for protection from most hacker attacks.
- Operating systems are messy: Echoes of your personal data -- swap files, temp files, hibernation files, erased files, browser artifacts, etc -- are likely to remain on any computer that you use. For example, when you encrypt and compress files, clear-text versions that existed before you compress/encrypt the file or clear-text copies that are created after you decrypt/decompress it may remain on your hard drive. It is not difficult to extract those echoes.
- Further advice about how to use encryption are discussed in Encryption is Not Enough, including what you need beyond encryption to be sure your private data is not lost or exposed.
New encryption applications often appear when an individual reads up on applied cryptography, selects or devises an algorithm, maybe even a reliable open source one, and then implements a user interface, tests the program to make sure it works, and thinks he's done. They are not. Such a program is certain to harbor fatal flaws.
"Functionality does not equal quality, and no amount of beta testing will ever reveal a security flaw. Too many products are merely buzzword compliant; they use secure cryptography, but they are not secure." --Bruce Schneier, in Security Pitfalls in Cryptography
- 7-Zip offers strong encryption, but it is not convenient for use with cloud applications.
- However CryptSync, which utilizes 7-Zip is convenient, particularly if you use the "Run in background" option. It also has the advantage of allowing multiple pairs of encrypted/unencrypted folders.
- Encryption is Not Enough offers further cautions on encryption, and on what you need to do beyond encryption to be sure your private data is not lost or exposed.
- Best Free File Encryption Utility has reviews of programs used to encrypt files and/or folders directly.
- Best Free Drive Encryption Utility has reviews of programs used to encrypt entire drives, including partitions and removable storage media like USB drives.
- Best Free Encrypted Virtual Drive Utility reviews programs used for on-the-fly encryption of files and folders.
- Best Free Encryption Utility for Personal Use at Work reviews alternative encryption programs that you can use in portable mode.
TrueCrypt is the seasoned but abandonded predecessor to VeraCrypt. It once met my criteria for selecting encryption software. The developers of TrueCrypt dropped a bombshell though. It's complicated.... TrueCrypt did pass a preliminary independent audit in 2015, but the dereliction of TrueCrypt now changes everything. For example, recent (September, 2015) vulnerabilities (which will never be patched) have been discovered in TrueCrypt.
Bizarre story behind TrueCrypt: The Atavist Magazine ran a special 7 episode series, The Mastermind, on the backstory of TrueCrypt and it's demise. [Index at Longform.org] It's a great read. Certainly more surprising than fiction. You can deduce a more plausible truth about the origins and demise of TrueCrypt from that series than from any of the many other stories on the internet. Scroll down to the bottom of each page to find the link to each next episode.
Common ways to implement on-the-fly, sometimes called transparent encryption
There are pitfalls and limitations in most systems for cloud-storage encryption. Perhaps you can spot them below, but this list might be best used as a reminder. Go learn more about these encryption methods in the Selecting an Encryption Method for Cloud Storage article and then come back here.
Type 1 = [Unencrypted folder] << >> [Integrated encryption & cloud sync] << >> [Cloud storage]
Examples: Tresorit | SpiderOak
Type 2 = [Virtual Drive - virtual clear-text files] << >> [Encryption] << >> [Folder - encrypted files] << >> [Cloud sync] << >> [Cloud storage]
Examples: BoxCryptor | Cryptomator | Cloudifile |
Type 3 = [User Folder - clear-text files] << >> [Encryption] << >> [Folder - encrypted files] << >> [Cloud sync] << >> [Cloud storage]
Type 4 = [Virtual drive - clear-text files are virtual only] << >> [Encryption] << >> [Encrypted volume - single encrypted file] << >> [Cloud sync] << >> [Cloud storage]
Examples: VeraCrypt | TrueCrypt (not recommended, see in Related Products and Information below)
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