# Cryptography help

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 alot

## Answers and Replies

kpros,

was this assigned as a homework problem in a class?

just curious.

DJ

Hi,
no I am just trying to solve them from a book I study these days..

Hi,
no I am just trying to solve them from a book I study these days..

Kopros,

What's the name of the book?

DJ

Introduction to Cryptography by Johannes Buchmann

I'll see if I have a copy. DJ