# Indistinguishable encryptions and CPA-secure example

Let $$F$$ be a PRF and $$G$$ be a PRG with expansion factor $$n \to n +1$$ For the following encryption scheme, decide whether it has indistinguishable encryptions and whether it is CPA-secure.

Given $$k \in \{0,1\}^n$$, to encrypt $$m \in \{0,1\}^{2n}$$, parse $$m$$ as $$m_1\|m_2$$ with $$|m_1| = |m_2| = n$$ then choose uniform $$r \in \{0,1\}^n$$ and output the ciphertext $$\langle r, m_1 \oplus F_k(r), m_2 \oplus F_k(r+1) \rangle$$

I would need help to give a proof about if this ES is CPA secure or not, or at least some tips/ideas to try by myself first.