New answers tagged

1

Some hints: A pseudorandom function must be a deterministic function from its key and input to its output. Moreover, the outputs should “appear random and independent” when the key is chosen randomly (and fixed) and the inputs are chosen by the attacker. For (a): in a CPA-secure encryption scheme, can Enc be deterministic in this way? Why or why not? For (b):...


1

For the sake of readability we adjust the notation somewhat. Let $\Pi=(Gen,Enc,Dec)$ be a $\mathsf{CPA}$-secure public-key encryption scheme with message space $\mathcal{M}$. We wish to prove that $\Pi^2=(Gen^2,Enc^2,Dec^2)$, with message space $\mathcal{M}\times\mathcal{M}$ is also $\mathsf{CPA}$-secure, where $\underline{(pk,sk)\gets Gen^2(1^n)}$: $(pk_\...


Top 50 recent answers are included