# Tag Info

Let $a$ and $b$ be the numbers emited rsp. by person A and person B. $E(x)$ means encoded form of $x$. $E(a)$ and $E(b)$ are publicly known, right? Note that if person A knows $a$, $E(a)$, $E(b)$ and person B knows $b$, $E(a)$, $E(b)$ and it is possible to calculate $a+b$ from $E(a)$ and $E(b)$ (that is what you want to do, right? So it must be possible) ...