# IND-CPA security scheme [duplicate]

Possible Duplicate:
CPA Secure Chosen plaintext scheme

The example for IND-CPA secure schemes given is generally:

for a random r,

$Enc_k(m) =(r|| E_k(r)$ $XOR$ $m)$ where $E$ is a $PRF$

But does the role of r and k really matter--i.e. isn't this equally secure?

$Enc_k(m) =(r|| E_r(k)$ $XOR$ $m)$ ?

## merged by Hendrik BrummermannNov 2 '12 at 15:04

This question was merged with CPA Secure Chosen plaintext scheme because it is an exact duplicate of that question.