(a) You are provided with the following:

A. An RSA facility complete with public/private key pair
B. A CBC (cipher block chaining) facility incorporating the IDEA block cipher
C. A message digest facility employing the MD5 algorithm

(i) You are required to send a block of data of size 1 MByte through an insecure network to a recipient who knows the message digest algorithm you are using, your secret key in IDEA and your RSA public key. Explain how you would use your security facilities (each facility for one operation) to provide the security services of privacy, message integrity and source authentication.

(ii) How would you achieve the above if the RSA facility were not available?

(iii) Discuss the relative security strengths of your solutions to (i) and (ii)

(b) (i) Name five functions that should be provided by a public key infrastructure.

(ii) Is it possible to operate a public key security system without a public key infrastructure? Justify your answer.

(iii) Discuss the security impact of not having a public key infrastructure.