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### Course: Computer science theory>Unit 2

Lesson 3: Cryptography challenge 101

# Checkpoint

Congratulations, you've made it this far!
You likely haven't decrypted the secret message found in The Discovery just yet.
Don't worry, some users report taking at least 3 weeks to work through the process without any further hints.
You have two ways to complete this challenge Master or Apprentice.
Master
This is for users who want to decrypt without any further hints. No easy task. You can continue grinding away and when you are ready, answer all of the questions in Crypto Checkpoint 2 & 3 without using the hints. Remember, hints usage can be tracked through your profile.
Apprentice
This is for hard working users who are still stuck, yet determined to finish. We applaud your grit. You can continue on to Crypto Checkpoint 2 and feel free to explore the hints. The hints will give away information related to the encryption. Hopefully these hints will lead you towards the solution after which you can go on to Crypto Checkpoint 3.
The police are awaiting your information...

## Want to join the conversation?

• Can someone clarify the question from checkpoint2:
In the final code, what would be the value of the following pad?
Does this mean translate the pad into binary?
or use this pad to translate the first part of the message
or something else.
the hint says
The answer is a sequence of 18 binary digits
For example: HELP = 0100
using that I produce 18 0/1's based on the pad phrase,
101001100100100110
but not correct.
the 'tooltip' when you click in the answer box is:
acceptable formats is an integer, like 6.
• I don't really want to complain.... but I feel like the practice (the next 2) are kinda impossible, since I don't know any of the things beforehand, since they don't teach us such thing.
• This is honestly much too hard... I've spent about 4 hours trying to do the crypto checkpoint 2. I don't understand a thing... I'm just gonna move on.
• I got a few questions, In Crypto Checkpoint 2 it seems like they wan't you to know these things beforehand. It never explains it in any of the previous ones. Am I missing something?
• Which hints is it talking about, is it the ones on the exercises, or is it the hints on the clues?
• The ones in the exercises. You can use the hints listed here, and anything you can figure out from the comments.
• I am so stuck on:
What values do you get after you XOR the following message with the given pad?
(use same encryption technique using in final code)
message: hi

that it is not even funny. Nothing i have tried is working, any help?
• I've heard (where y is a vowel) that you use 0 for consonants, and 1 for vowels.
So, if I changed gwang ho, it would be 00100 01
• Why would somebody leave those clues like a trail? Unless they were false. Like who would toss a bag with a clue out of there car?
• I am so lost at this point, trying to figure out how to understand what the angle symbols are and what the clue to translate them
• The angles represent sets of numbers in base 4. The first step is to convert the angles into sets of 2 numbers, and convert the whole thing into base 2.
Hint:
``      0      |   3------|------ 1      |   0      2``

(Clue #4 Pictures 3 and 4 starting at "These notes look like...")