Computer Science 530 - Assignment #1 -- Fall 2007

Due: Wednesday, September 26, 2007, 11:00 p.m.

1. When using the cipherblock chaining mode of operation for DES, 3DES, or AES: (50 points)
   1. What is the purpose for using an initialization vector. For proper operation of this mode of operation who must know the initialization vector, and for the security of this mode of operation, who, if anyone, must be prevented from knowing the initialization vector. Why?
   2. For proper operation of this mode of operation who must know the encryption key, and for the security of this mode of operation, who, if anyone, must be prevented from knowing the encryption key. Why?
   3. For proper operation of this mode of operation who must know the decryption key, and for the security of this mode of operation, who, if anyone, must be prevented from knowing the decryption key. Why?
   4. For proper operation of this mode of operation who must know the ciphertext, and for the security of this mode of operation, who, if anyone, must be prevented from knowing the ciphertext. Why?
2. You are building a system that uses digital signatures for document authentication. You will use a hash function to generate a message digest of the document to be signed, and will encrypt the digest with the private key of the signer. What properties will you require of your chosen encryption algorithm, and why are each of these properties important? In particular, explain any properties that must be met regarding the relationships of the keys in the system. Suggest a choice of cryptosystem and justify your choice. (50 points)

INSTRUCTION:

The report must be submitted by 11:00 p.m. on September 26, 2007. The report should be approximately 3 pages, or roughly 1200 to 1500 words. To submit your report you will use the DEN Blackboard assignent submission mechanism. You will use this method regardless of whether you are an on-campus student or a DEN student.

How to submit Assignment #1:

• STEP 1. Please login to DEN, and select csci530.
• STEP 2. Please select "Assignment" in the menu.
• STEP 3. Please select "view/Complete Assignment #1".
• STEP 4. Please select "File To Attach" to attach your report. (NOTE: PDF, MS WORD, ASCII TEXT ONLY! Other formats are NOT acceptable.)
• STEP 5. Please select "Submit" button. (If you select *SAVE* button instead of *submit*, then the TA cannot view your report for grading.)

It is the individual student's responsibility to follow the submission instruction. Submissions that do not follow this instructions, e.g., submitted late, or only "Saved" and not submitted. may be penalized or may not be graded at all. Note that the submission box for the assignment may dissapear from the class web site at 11PM on September 26th, i.e. the submission deadline.

GUIDELINE:

This is a lot to cover in so few words - so our advice is to write a first pass at your answer that is longer, and then edit out material that is redundant or not to the point. The use of tables can be very effective in conveying your ideas in a small area, but the tables must be integrated with your textual discussion, and not the only item in your submission.