IT430 E-Commerce Assignment No.4 Fall Semester 2013 Due Date 24/1/2013

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IT430 E-Commerce Assignment No.4 Fall Semester 2013 Due Date 24/1/2013


Assignment No. 04
Semester: Fall 2012
IT430 E-Commerce
Total Marks: 20
Due Date:24/01/2013
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Assignment
Question no 1: 20 Marks
Assume you as a student is playing role of customer in E-cash payment system in which anonymity of the buyer is
kept in view. You have purchased online Electronic Project essentials from online Supporting Company ABC that
has also registered its account in the E- Cash bank.
You have to pay to merchant using the mentioned e-cash system following facts help you to calculate your coins
minting and paying to customer anonymously.
For signatures you have to adopt the following mathematical expression:
Steps for Solving the Problem:
Serial #.re (Mod m)
“r” =((your ID ‘s least significant right most two digits) Mod 4)+2

Here “r” will vary according student to student based upon their VU ids and Mod here mean well
known “modulus” operator.
For example in case of your id is BC1304017001 pick the last two digits here these are 01 and take Modulus
operator with digit “4” “01” Mod 4=01 and apply the attained “r” in the minting and depositing stages of the
payment to Merchant all other factors are same for all students only the variation will be attained according to
factor “r” which will be calculated according to the above mentioned formula.
Public key of the bank consists of modulus ‘m’ and a no. ‘e’. Here for simplicity of calculation you have to take
“m=7” and “e=3” it has been assumed all constraints of the system for taking values have been followed.
Serial # =00100.
And code sent back by bank using the following mathematical expression.
(Serial #.re) d (mod m)

Here “d=1/3” for all students for cause of simplicity. And you people have to mint coin having value
of “5$” in simple words multiply with “5” to all values “e” and “d” in all given above and below
mathematical expressions in assignment to calculate the correct value to mint five dollar coin . And
this is our own way to generate message digests to encrypt the values for security purposes.
And code again decoded by you using the following mathematical expression.
[(Serial #.re) d (mod m)]/r

Here you have done minting stage and after decoding stage you can sent that achieved values to
merchant to pay the merchant the five dollar coin value using the following concatenation expression
. Which he /she herself send to e-cash bank to get credited.
Coin = (Serial#) ([(Serial #.re) d (mod m)] /r )) ((Serial #.re) d (mod m) )
Note: Here for coin generation you have just concatenated the expressions or values to get the coin value.
DISTRIBUTION OF MARKS ALONGWITH TABLE TO BE FILLED:
Observe all the above guidelines and rules as mentioned above to fill the following table to get graded your
assignment. Think with peace of mind and heart to go to the actual calculations. Think beyond the
boundaries to devise your own ways to decrypt and encrypt your messages to get the task done.
Message/Code
sent by you to
bank after
your
signatures
Message/Code
minted by
bank and sent
to you
Message
Code
decoded by
you
Coin Why is there
anonymity
factor
achieved by
customer
(One
sentence
answer)
Why we
have
taken
d=1/3
and e=3
Marks 4 Marks 4 Marks 4 Marks 4 Marks 2 Marks 2
Best of luck with new thinking dimensions for your own!
Note: Your Assignment # 4 covers Lecture#25 to Lecture#33 complete.
Deadline:
Your assignment must be uploaded/submitted on or before 24st January 2013.