Hi Professor,

I attended today's class online and I have question about Chinese Wall Rule for Read and Write as I am a bit confused on how these rules work

If I understood this right, Subject S can read a company C' data only in two circumstances:

- If he has already accessed C' data

- He has NOT accessed the competitor's data

For example: and in slide 43, if S reads from Bank A, he cannot read from Bank B. or if he read for School 1 he cannot read from School 2...

For write rule:

S can write to O only if S can read O and all objects that S can read are in the same dataset as O. Does this mean that if S wants to write to Bank A, he shall not be accessing any other banks/schools prior to that?

As the slide notes:  Subject S is allowed to read from at most one company dataset inany  CI

To my understanding if S wants to write to Bank A he shouldn't have any prior access to School 1. The example in slide 44 actually wants to show what will happen if S reads from Bank 1 and writes to school 1; then S' may find out information about school 1 and Bank B (conflicts of interest).

As in the same slide there is a note: This is intended to prevent an indirect flow of information that would cause a conflict of interests.

Many Thanks,

Gayaneh Petrossian

Sorry for this late reply! I was out of town and just came back yesterday.

Your understanding of both rules is correct.

This example on slide 44 is actually a counter example. It shows that if we allow this to happen, we may violate the write rule. So, if S reads from bank 1, he/she CANNOT write to school 1.

Dr. Guo