Homework Assignment #1

Homework Assignment #1
Due: 3/24/2010 (Wednesday)
1. Argue the advantage and disadvantages of secret-key (one-key) and public-key
(two-key) encryption methods.
2. This problem is about the RSA system. Let n=pq=139x313=43507.
(1) Let the public key e=29. Compute the corresponding private key d.
(2) Encrypt the message M=“rsa is the first public key encryption system”. The
English characters are converted into 0 to 25 and the space is 26.
(3) Consider M as a binary string by ASCII code. Use a hybrid encryption
method of RSA and DES to encrypt the above message M. You can run the
DES program in Programming Assignment #1.
(4) Let the verification key e=31. Compute corresponding signing key d.
(5) Let M be hashed into the hash value 2B5X. Compute the digital signature of
(6) Verify whether 1342 is the digital signature of the hash value 4762?
3. This problem is about certificates.
(1) What is a certificate?
(2) How and where is it used?
(3) Get a certificate from your computer and describe its important items.
4. Find an implementation on the Internet and compute the hash values of the
following strings:
(1) “MD4 is not secure”
(2) “MD5 is not secure”
(3) “rsa is the first public key encryption system”