# What is the difference between RCCA and CCA2?

Well, I know it's easy to tell CCA1 from CCA2, but I failed to find the difference between RCCA and CCA2.

What is the difference?

In the indistinguishability game (IND), this difference is translated in the restrictions to the use of the decryption oracle in phase 2. In CCA-2, the adversary is not allowed to ask for the decryption of the challenge ciphertext $c^*$, while in RCCA, if the adversary asks for the decryption of any ciphertext that decrypts to the challenge messages $m_0$ and $m_1$, he will only receive a special symbol $\mathsf{test}$.
• No; in RCCA you can "ask for the decryption of" "the challenge messages $m_{\hspace{.02 in}0}$ and $m_1$"; you'll just get a special response if you do. ​ ​ – user991 Dec 17 '15 at 21:18