Does Frequently Encrypting/Decrypting Files Degrade Them?

[Brandonn2010]

Does repeated encrytion and decryption of files corrupt them over time? I use 7-Zip

[Hungry Man]

Not really, no.

[Nebulus]

There is no reason for files to become corrupt , unless the tool used to manipulate them has a serious bug...

[dantz]

I'd say theoretically yes, and in practice generally no.

Hardware-related bit errors occur all the time in hard disks, RAM, CPU, onboard circuitry etc. Various error-detection and correction algorithms are able to handle the vast majority, but the small percentage that are undetectable or unrecoverable are able to slip through and corrupt data. Theoretically every time you 'touch' a file (edit, move, copy, encrypt, decrypt, defrag, etc.) it increases the chances that errors will occur to that file or on that disk, especially if the CPU or RAM are faulty or are operating out of spec (e.g. overclocked, overheated, mismatched etc.). However, even untouched data on unused media will develop bit errors over time. And software-related data corruption is even more likely to occur.

In a properly functioning system I would expect the theoretical increase in data corruption due to encryption/decryption operations to be quite small. However, if the encryption key itself happens to become corrupt then the consequences can be devastating, which is why it's always smart to keep multiple backups of encrypted data.

[lotuseclat79]

Is 7zip even a serious form of encryption? I thought is was only one of many forms of compression which has nothing to do with encryption.

-- Tom

[Hungry Man]

It uses 128bit and supports 256bit AES.

[LockBox]

Of all the compressed/archive encryption, I see SecureZip used most often in business as they are certified Hippa/SO/fips 140 compliant (this is not your father's .zip). SecureZip, by far, has the most solid security structure, from file wipes to memory wipe to integrity checks (MAC), AES, etc. Of course, you also pay for all this - $39.95.

[chronomatic]

Originally Posted by dantz

I'd say theoretically yes, and in practice generally no.

Hardware-related bit errors occur all the time in hard disks, RAM, CPU, onboard circuitry etc. Various error-detection and correction algorithms are able to handle the vast majority, but the small percentage that are undetectable or unrecoverable are able to slip through and corrupt data. Theoretically every time you 'touch' a file (edit, move, copy, encrypt, decrypt, defrag, etc.) it increases the chances that errors will occur to that file or on that disk, especially if the CPU or RAM are faulty or are operating out of spec (e.g. overclocked, overheated, mismatched etc.). However, even untouched data on unused media will develop bit errors over time. And software-related data corruption is even more likely to occur.

True unless you use a filesystem like ZFS which prevents such corruption all together.