Consider a public key, secret key pair where the public key is

$$

P and the secret key is

$$

S$.$ The encryption algorithm for a message

$$

x and a key

$$

z is

$$

$($

$$

$,$

$$

$)$

E$($x$,$z$),$ and the decryption algorithm for a received message

$$

y and a key

$$

z is

$$

$($

$$

$,$

$$

$)$

D$($y$,$z$).$

What is

$$

y such that

$$

$($

$$

$($

$$

$,$

$$

$)$

$,$

$$

$)$

$=$

$$

D$($E$($x$,$P$),$y$)=$x$?($In terms of possibly

$$

x$,$

$$

P$,$ and

$$

S$?)$