Hi I have stuck at these two exercises ...

1)

Suppose we use the Rabbin protocol and we have chosen p=31,q=51 and B=15. If we want to transmit the message M=20 which will be the encrypted message C?? Also what are the messages the recipient will receive decrypting C ??

2)

Suppose we work in RSA and Alice has the public key (n,e)=(667,3). Suppose m1=26, m2=46, and the signature of Alice in m1 is sig(m1). We want to find sig(m2). We have the right to give her a message x, x different from m2 and she will sign it. We can't use the factoring of 667 neither can we find the d from e=3. What message should we give her???

thnx a lot xxx