Encryption of Encrypted data

Question

Is it possible to encrypt encrypted data, using multiple programs so that in order to decrypt you would need both programs? Not really sure if this is possible but just wondering if it was a thing and if it is practical if the data doesn't need to be used often.

Answer 1

Is it possible to encrypt encrypted data ..

Yes, in fact, chances are there are multiple layers of encryption on the socket you're using to view this web page.

A lot of different file/disk encryption programs even ask if you'd like to encrypt your data using multiple algorithms (e.g. using AES-256 followed by Blowfish, or some other algorithm).

When you encrypt something using multiple layers of encryption, it's not that you need different programs to decrypt, just that the program you're using to decrypt can properly decrypt the algorithm used at each layer, and more importantly that you select the correct order of algorithms when decrypting.

I was also wondering if encrypting it again would make it almost uncrackable, or if it would be the same as normal encryption

To this; no encryption is completely "uncrackable". Even AES has a known vector of attack, but more specifically, it's about entropy, or how long it will take to brute force the password, and knowledge of the algorithm used.

If I know that a file was encrypted using one of the DES algorithms, I could probably throw together a small beowulf cluster and brute force the password relatively shortly (within a few weeks or less). If I were to receive the same file but had no clue what algorithm was used (DES/AES/Blowfish/etc.), then more investigation would have to occur before I could attempt to crack it properly (or I could throw it to the various "crackers" while I'm investigating, knowing that it might be a waste of computational time).

Certain algorithms are known to have attack vectors that shorten the brute force time (like collisions, etc.), and thus are less secure than others, so knowledge of what container/algorithm was used shortens the time to brute force the encryption.

With that, if you were to encrypt a file with different algorithms, this just increases the time it would take to brute force the file. Mind you, if you use weak encryption for all levels, "time" is a relative term.

In the end, it just like picking a lock:

• How much time am I willing to invest in picking the lock?

• Is what's behind the door that valuable as to warrant me spending that time on picking the lock?

• Is what's behind the door that valuable as to risk being caught during the time it takes to pick the lock?

If someone else has something of value behind a less secure door, chances are I'll go for that door over yours.

Hope that can help.