Assignment No. 04 IT430 E-Commerce Due Date:24/01/201

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Question no 1: 20 Marks

Assume that you as a student are playing a 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
minting coins 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 BC1304017001. You need to 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. You 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 sends 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. 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 : Marks 4
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Message/Code minted by bank and sent to you : Marks 4

Message Code decoded by you : Marks 4

Coin : Marks 4

Why is there anonymity factor achieved by customer (One sentence answer) : Marks 2

Why we have taken d=1/3 and e=3 : Marks 2

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Solution Coming soon