Answered Essay: Exercise 1. Compute the Round 1 DES key given the original key input is

Exercise 1. Compute the Round 1 DES key given the original key input is

K[0] = 0101010101010101HEX

Note: Here we’re assuming odd parity bits.

Expert Answer


Numbers 14 17 11 24 1 5 3 … come from permuted choice PC-2. To explain 16 round DES key scheduling:

DES input key size is 64 which contains 56 bit key and 8 bit parity. Parity bits are 8th bit of every 8 bit (one byte). So they are all multiple of eight: 8, 16, 24, 32, 40, 48, 56 and 64. Permuted choice PC-1 is used to remove these bits from the 64 bit input key. So PC-1 gives 56bits as output.

In round i (1 <= i <= 16), there is a 56 bit input, C_(i-1) as left half and D_(i-1) as right half (each 28 bit). These two halves are rotated left (for decryptionright rotate is used). In encryption, rotate amount in rounds 1, 2, 9 and 16 is one and in other rounds it’s two. In decryptiononebit right rotation in rounds2,9,16 and two bit right rotation in all other rounds. As inputs of rotation are C_i and D_i, outputs of rotation are C_(i+1) and d_(i+1) which are passed to the next round,i+1, as input.

After all, in round i there is a 48 bit output, named K_i. This sub key is generated from permuted choicePC-2, which takes C_i and D_i as a 56 bit input and outputs the sub key.

Buy Essay
Calculate your paper price
Pages (550 words)
Approximate price: -

Help Me Write My Essay - Reasons:

Best Online Essay Writing Service

We strive to give our customers the best online essay writing experience. We Make sure essays are submitted on time and all the instructions are followed.

Our Writers are Experienced and Professional

Our essay writing service is founded on professional writers who are on stand by to help you any time.

Free Revision Fo all Essays

Sometimes you may require our writers to add on a point to make your essay as customised as possible, we will give you unlimited times to do this. And we will do it for free.

Timely Essay(s)

We understand the frustrations that comes with late essays and our writers are extra careful to not violate this term. Our support team is always engauging our writers to help you have your essay ahead of time.

Customised Essays &100% Confidential

Our Online writing Service has zero torelance for plagiarised papers. We have plagiarism checking tool that generate plagiarism reports just to make sure you are satisfied.

24/7 Customer Support

Our agents are ready to help you around the clock. Please feel free to reach out and enquire about anything.

Try it now!

Calculate the price of your order

Total price:

How it works?

Follow these simple steps to get your paper done

Place your order

Fill in the order form and provide all details of your assignment.

Proceed with the payment

Choose the payment system that suits you most.

Receive the final file

Once your paper is ready, we will email it to you.


Let us write that nagging essay.


Submit Your Essay/Homework Instructions

By clicking on the "PLACE ORDER" button, tell us your requires. Be precise for an accurate customised essay. You may also upload any reading materials where applicable.


Pick A & Writer

Our ordering form will provide you with a list of writers and their feedbacks. At step 2, its time select a writer. Our online agents are on stand by to help you just in case.


Editing (OUR PART)

At this stage, our editor will go through your essay and make sure your writer did meet all the instructions.


Receive your Paper

After Editing, your paper will be sent to you via email.