
  So to clarify then the question would be this: The attacker has the encrypted data and the plain text key and no other knowledge. How easy is it to decrypt the data and why.


As I understand it, modern ciphers can't be broken knowing just the ciphertext (and no other information). But, the cipher algorithym (eg. AES) is only one part of a wider system using RNGs, keys, salts, IVs, padding, signatures, certificates, and so on. People have developed amazing exploits against tiny deficiencies in how those parts all fit together. So even though the ciper itself is secure, that does not mean that the system as a whole is secure.

Here's a simple analogue. SCUBA tanks have a threaded hole where the valve screws in. Some of those holes use a "3/4 NPS" thread, others use an "M25" thread. An M25 valve will screw "perfectly" into a 3/4 NPS hole - but those two threads aren't quite the same. Result: the valve can explode from the tank when it is pressurized. Each component is fine on its own; they seem to fit together correctly; an amateur won't see any problem; but the resultant system can fail catastrophically.

Crypto's the same!

TC

AES 256 Encryption - Is it really easy to decrypt if you have the key?
Is it possible to use Flatiron's resourcefull (ODM) in express.js?
