Online quest from MBLTdev: prizes and answers

    Hello, Habr! On Wednesday, we washed down the quest , and judging by the stream of comments and messages, you liked the quest and made you break your head. We are glad! In this post, to summarize: we will reveal the correct answers and give prizes.

    Statistics




    Prizes


    Today the prizes went to the winners, check the mail.

    • The annual subscriptions for JetBrains products were received by Insaf, Mikhail and Daniil.
    • Tickets for the MBLTdev 2017 Mobile Developers Conference - Alexey Laguta, Mikhail and Artyom.
    • T-shirts MBLTdev 2017 - Ustinov Valery, Ruslan Akhtyamov and Pavel Kamaev.
    • A 20% discount on tickets for MBLTdev 2017 is our gift to everyone who completed the quest to the end.

    Now we will tell you how to solve the tasks. Under the cut - answers.

    Quest entry


    Task: on the promotional video you need to make out a link to the quiz.

    Solution: You will need a sharp eye and a slow-motion function on YouTube. We get the coveted link.



    First level


    Task: decrypt the text.



    Solution: listing is presented, perhaps, in the most popular esoteric language - Brainfuck . To solve it, it was enough to find the language interpreter and get the answer: Mobile app developers love the MBLTdev.

    Second level


    Task: there are two hashes on the screen, you need to find the third.



    Solution: by trial and error, we determine that sha1 is used, and we get the answer: f5fbaef89c6a66b135a5e00947a45932d9f1e8a6.

    The third level (we know he especially amused you amused)





    Objective: Encrypted text is presented. We did not ask to decipher the phrase. It was necessary to give an answer that is encrypted. The answer should also be in the source cipher format.

    Solution: suppose the text is encrypted with “Caesar’s cipher”. When the alphabet is shifted 17 points to the right, we find the source text:



    = "Functions that use the base type should be able to use subtypes of the base type without knowing it." This is the Barbara Lisk Substitution Principle. Many tried to enter the decrypted text, the name of the principle in different languages, the abbreviation, but only received the answer:



    Let's try to go by the principle:



    To do this, we determine the amount of displacement of the alphabet in the original phrase:



    We find the initial text at position 16, therefore we encrypt the phrase “Barbara Liskov Substitution Principle” with the 16th offset: Yaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa Also valid are the answers of Barbara Liskov and Liskov - Rparpap Yshbyus and Yshbyus respectively.

    Fourth level


    Task: specify the coordinates.



    Solution: In quizzes of this kind, a frequent question is the question of coordinates. The clue is the mask after nay: and nrbi: Do you



    need to understand what nay and nrbi mean? Here, everything is simple and complicated at the same time: giving an explicit hint to lat and long would be too obvious, so we wrote these frequent expressions with the Dvorak layout .
    The coordinates were considered with an error and it was enough to enter at least 4 characters after the decimal point. The correct answer is 55.7407, 37.6090.

    Fifth level





    The answer is in the picture. Literally. You must open the picture in any text editor:



    Agree, it was fun. And at MBLTdev 2017 it will be even more fun: useful reports and acquaintances + Codelabs and quizzes for iOS and Android developers with cool gifts. See you October 27th! Register today.

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