What is null key encryption ?

Question

In the movie Dark Knight, the batman builds some ultra powerful sonar monitoring system and encrypts it will Null Key Encryption.

I was reading this RFC but couldn't comprehend it. It says something like this

However there are cases when only authentication and integrity protection is required, and confidentiality is not needed or not permitted.

And in the end he tells Fox

Type in your name when you are finished.

If its that simple, why encrypt it ?

Answer 1

There is no Null Key Encryption. It is just plain fiction.

The RFC you linked is a... fun RFC? The Null Algorithm described there is indeed a very very powerful algorithm. It encrypts your plaintext

Hello World

To the ciphertext

Hello World

I heavily doubt this algorithm will ever be broken :-)