Problem Set 2: Crypto

tl;dr

  1. Watch Week 2’s lecture.

  2. Infer a user’s initials from their name with initials.c.

  3. Choose two adventures:

    • Implement Caesar’s cipher.

    • Implement Vigenère’s cipher.

    • Crack passwords.

  4. Submit your code.

  5. Submit a form.

Help

For help with Week 2 and Problem Set 2:

  • Watch Zamyla’s walkthroughs herein.

  • Start a discussion with classmates.

Reminders

Per Week 2’s lecture:

  • Use help50 as needed.

  • Use eprintf as needed.

  • Use debug50 as needed.

Getting Started

Alright, here we go again!

Log into cs50.io and execute

update50

within a terminal window to make sure your workspace is up-to-date. If you somehow closed your terminal window (and can’t find it!), make sure that Console is checked under the View menu, then click the green, circled plus (+) in CS50 IDE’s bottom half, then select New Terminal.

Next, execute

mkdir ~/workspace/pset2/

at your prompt in order to make a directory called pset2 in your workspace directory.

Now execute

cd ~/workspace/pset2/

to move yourself into (i.e., open) that directory. Your prompt should now resemble the below.

~/workspace/pset2/ $

If not, retrace your steps and see if you can determine where you went wrong. You can actually execute

history

at the prompt to see your last several commands in chronological order if you’d like to do some sleuthing. You can also scroll through the same one line at a time by hitting your keyboard’s up and down arrows; hit Enter to re-execute any command that you’d like.

What to Do

  1. Implement either of:

  2. Implement any two (2) of:

FAQs

Not a directory

If you execute, e.g.,

cd ~/workspace/pset2/initials/

and see

bash: cd: /home/ubuntu/workspace/pset2/initials/: Not a directory

odds are you don’t have a pset2/ directory inside of ~/workspace/ and/or you don’t have an initials/ directory inside of ~/workspace/pset2/. Check as much using ls (remember how?) or poke around your IDE’s file browser at left. Make sure that:

  • you have a pset2/ directory inside of ~/workspace/,

  • you have an initials/ directory inside of ~/workspace/pset2/, inside of which is initials.c,

  • you have an caesar/ directory inside of ~/workspace/pset2/, inside of which is caesar.c,

  • you have an vigenere/ directory inside of ~/workspace/pset2/, inside of which is vigenere.c, and/or

  • you have an crack/ directory inside of ~/workspace/pset2/, inside of which is crack.c.

How to Submit

Be sure you’ve signed up for a GitHub account, per Problem Set 0, and that you’ve logged into and authorized CS50.me at least once, per Problem Set 1!

Step 1 of 4

Execute update50 again to ensure that your IDE is up-to-date.

Step 2 of 4

  • Recall that you were asked to implement the less-comfortable or more-comfortable version of initials.

    • Be sure that initials.c is in ~/workspace/pset2/initials/, as with:

      cd ~/workspace/pset2/initials/
ls

  • Recall that you were asked to implement any two (2) of caesar, vigenere, and crack.

    • If you implemented caesar, be sure that caesar.c is in ~/workspace/pset2/caesar/.

    • If you implemented vigenere, be sure that vigenere.c is in ~/workspace/pset2/vigenere/.

    • If you implemented crack, be sure that crack.c is in ~/workspace/pset2/crack/.

Step 3 of 4

  • To submit the less-comfortable version of initials (if you implemented it), execute

    cd ~/workspace/pset2/initials/
submit50 cs50/2017/x/initials/less

    inputting your GitHub username and GitHub password as prompted.

  • To submit the more-comfortable version of initials (if you implemented it), execute

    cd ~/workspace/pset2/initials/
submit50 cs50/2017/x/initials/more

    inputting your GitHub username and GitHub password as prompted.

  • To submit caesar (if you implemented it), execute:

    cd ~/workspace/pset2/caesar/
submit50 cs50/2017/x/caesar

  • To submit vigenere (if you implemented it), execute:

    cd ~/workspace/pset2/vigenere/
submit50 cs50/2017/x/vigenere

  • To submit crack (if you implemented it), execute:

    cd ~/workspace/pset2/crack/
submit50 cs50/2017/x/crack

If you run into any trouble, email sysadmins@cs50.harvard.edu!

You may resubmit any problem as many times as you’d like.

Step 4 of 4

Submit this form!

Your submission should be graded within 2 minutes, at which point your score will appear at cs50.me!

This was Problem Set 2.