Alice uses an RSA algorithm with the private key Ks and the public

key KP given by $(5,247)$ and $(21,247)$ respectively.

Alice wants to sign a contract before sending it to her lawyer. The key

Alice must use is given by:

$($a$)(4,247)($b$)(5,247)($c$)(21,247)($d$)(3,247)$

Alice$$s lawyer uses an RSA algorithm with the private key Ks and the

public key KP given by $(3,247)$ and $(11,247)$ respectively.

Alice is worried about an unauthorised person gaining access to her

documents during transmission. Alice decided to double encrypt her

document using the following keys and order:

$($a$)(5,247),(11,247)($b$)(21,247),(3,247)($c$)(21,247),(11,247)$

$($d$)(3,247),(11,247)$

In applications which require the use of public and private key

encryption algorithms,

$($a$)$ both public key and private key are used for encryption $($b$)$

private key is used for key distribution and pubic key is used for

encryption $($c$)$ Public key is used for key distribution and private key

for encryption $($d$)$ both public key and private key are used for key

distribution