CAPTURE THE FLAG
How to Play
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Choose any puzzle by clicking on the corresponding box on the webpage. The point values are listed on each box.
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Solve the puzzle using critical thinking, logic, and your knowledge of electrical engineering. The answer to the puzzle will always be a password or passphrase.
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When you have solved the puzzle, enter the answer into the linked google form. Make sure you are signed in with your USC email, the form will automatically record your email address.
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Enter the password or passphrase in the google form. If you are correct, congrats! You have earned some points. If not, the form will not allow you to proceed and you have to try again. You are allowed infinitely many guesses.
Additional Rules
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Working in teams is encouraged! Puzzles are always more fun with friends. Make sure the same person submits the responses for each puzzle!
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If you have not done so already, join USC IEEE’s Slack channel!
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Feel free to message any of the ambassadors on Slack to ask for a hint. Hints will cost you points, however, so use them sparingly!
Puzzle 1
Rough Tough and Huffman
You have come upon a computer game where your possible movement options are the four cardinal directions (up, down, left, and right) plus the four diagonal directions (UL, UR, DL, DR). After some investigation, you come up with the following frequencies for these actions
U - 19.7%
D - 17.4%
L - 10.5%
R - 8.3 %
UL - 13.7%
UR - 11.2%
DL - 18.3%
DR - 0.9%
All of a sudden, you receive a stream of bits:
101111111000011010011001
Puzzle 7
065 032 104 097 109 032 115 097 110 100 119 105 099 104 032 119 097 108 107 115 032 105 110 116 111 032 097 032 098 097 114 032 097 110 100 032 111 114 100 101 114 115 032 097 032 098 101 101 114 046 032 084 104 101 032 098 097 114 116 101 110 100 101 114 032 115 097 121 115 044 032 226 128 156 083 111 114 114 121 044 032 119 101 032 100 111 110 226 128 153 116 032 115 101 114 118 101 032 102 111 111 100 032 104 101 114 101 046 226 128 157
Puzzle 8
If a chessboard were to have pennies placed on each square such that one penny was placed on the first square, two pennies were stacked on the second, four pennies were stacked on the third, and so on (doubling the number of pennies on each subsequent square), how many total pennies would be on the chessboard when all squares are filled?
Puzzle 9
Say you want to make a timer on your Arduino UNO using interrupts. Given that the Arduino UNO clock is fixed at 16 MHz, and you wish to have a delay of 0.1s between cycles, what must your prescaler and OCR1A values be (using the SMALLEST possible prescaler value)?
HINT: The prescaler must be one of the following powers of 2: 8, 64, 256, or 1024.
ANOTHER HINT: The OCR1A value you calculate must fit in at most a 16-bit register.
Puzzle 13
The one time pad can be cryptographically secure, but not when you know the key. Can you solve this?
You are given the encrypted flag, key, and a table to help.
Encryption: hgxiofhv iwf mtshluff xyiqxn
Key: uscecedepartment
Can you use this table to solve it?
HINT: Vigenere cipher problem
Puzzle 17
Find the number of sub-strings with the following properties in the given string:
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Length >= 2
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Contains only A's
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Bound on both sides by either the beginning of the string, the end of the string, or by any character other than a.
For example, lets take the string "aabaaacadaa". It contains three such sub-strings, indexes 0-1, 3-5, and 9-10. The sub-string from indexes 3-4 is not valid because it is bound on the right side by an "a". The character with index eight is not valid either, because although it is an "a" and is bounded by the correct characters, it only has a length of one.
The string:
caanqaaeamdwaagarapabseaawaabawaoaalaaaaaxxaapsxeaagragaaadawaoaanaawpqatdaaatakwsaaaayaaaaealabjxaaaeaaauamjawnsaataaaoaaqaxaaaaaeaajrahaaaaaadjaaqtewhspaaaaannaoaaaaaboaaaaaaaaaataqadihaaaaqawwaaazoaxaoapabuzwaaaaaaaahlaauakaaiyjavwcaasxaaturabanuataoikpkaoalaaaaaaafgaalwuxzaazaaltazjdaaasalraabaqjmaaadaaaaaaaaiauaqbajaaactaarwrcavmaaxxaqrxaaaaaaaeaaaqaajafaaadaciaaaakadraacafaahlaiaaaakefahalaaparxaaagaacnoraaytaloasaadaaaafataaoqarcazjmqeafajgaaaaaaavvaaaaaiaaaaiaaczrbalomaakgilacaayaayaxwaotaarlaxpaaraapaaaswhxxaajeagfaaaaeaaalaaaaeeaatoamayaaauaadaueccvaauvaakowasxaaatgnwaawtrxtudppfaaqfypaaaaanraiaaaynagqqaabdaayaaazaesasaaaaaaoaaaaacvawcasaiaaaavxafaqeaaadaciaaanujgxamxiaadazanaamaygabwrfazalaaawkpaalsaafiiataatavvaqaqzdatyaaaaanpsaaaajvaydxacyadaolabhocaaawaniniuaaakaaiaaanxaaxaccfaarlaakaabenevaaacaydaaxaaxepasmaasadabanaaafaalaladaagafaaaaaahagnixwemathayfagaxapkaaaafaasaacawaaaaackawamaaaawaatnaaoaaatbaniafawaalkaaumqzaoaauaamazaztamvdaxdaraeasaaaaachoavaaaqaajwaaaaaacarlaxaaapaaaaamfaaoeaoaaamapkacamraalbnavaaaxiaqazaamcmanagaicraawaaascbmraaavabaawaagqataazuaaaaakawxwazparaaaaaaaaasaiedhfaaaetaaaapaaapiaaaawembhmafalgayaaodamqazqwaasdeaappaacaarahnalaeaaaaanasasbzaaaaoaraeaazhaaevoiaazpypuggeayaapanzakaaaavzaacaaraaaaaaaxsvyacoxvttzgtbcuazxkuaaaiflbjzaaojaboxmaadkaaakzsbxaaaajanaatgaaaazarfaawujasaanxazowlfaayahaaaaaabdoayufltoaiabayaaafawiazaqaasaafchifgpjuvauaaayaaatvaxaaeaaharrazavlayaaaaaaagxcfaemvyaaaaaaulxajahazgapaasagswmahaapbaaafnaaywpagqiauaaaavbmgifaweatvaayhaadajaaaaragaminaafixwuaaexaajawzaazlaxastaatmdaaaaairfnraaaaaaaxaafgaattgakkaacioaabatahfqabmvzfzafifsbbnaaouaahalaahuaawaagataamarjgaaaamianabhaaaaaaiahtpxvaaaaaaahaahtgaaaazvafaaaavzkamalawaaqeaaaavgjkanenairaalazaaaayafsazaacodeawvamtdyaaaynaaxaazvssadaqdvstaaolcsecwszzaajahawajooaahgumavaabriwaazgrtaauaxpaaawbhaberaqltaaaaqaaaaxayldaaxgakmwmaaxxayualfaaijsaaaazxpaaaewcngnaaaypvmayaiaamaasaaakattsadqclclafadaaaadsnwdnaaqasataabasaataaaapajqatuakaygaaoamatgaacaaaaaljwzaaaqajafanaaxaagxqaaibgaslawuadeaaxbaweaxxaaaaesnaacatahaitatqsabkaaaaatlajpavaaadlnvzaeaascaaaahqmatanapciszqefcalacjraamhaaaaoanaganaaaaacaqcnaayaawaagazaayyaayjagasarbuafzpmpqeaohaaaglidaanrheaaaabnnaairalrbjuzaakaabgaeaadaaetaauaaaaazaadzxaaaagavazehulaauazvcaajcaaaaqgexaaaaajcirxauaahaoaaahohaanaayoaalukbaauaaaaioaaakcobkoaqdvalasraaawuaakaaaaaadamsaaaaaqakaanaxaaaiwaodazaanaaaravbqimznaataaesaavyqjakgabaeaiasamapaaaalwzaikpbclaaaacalakusaapaaaaqnaanaaahoaaaecaarwwaaaabxaaaaaepalaaaaaaaxaxgamawmalaaaaanqeaaaaxaomajaaaiavaaqxwaazaaaaaaaaapqpaaaaaastgdydwxaalahaiziaamauayaqaxyryaizkaefuaaaaaaaeaaanaaiaaaaayaaaaaaiywaaahaaaaajtawmanmadayaaawaaaaxagaaicaiagaaanaaakaodapaaaaabaaaaaadauevaaywbaaaaaaaaaaygaaawaazimwasraazoagvzpaabrnmlhqghhoaaanbaaanaaaaaqxauaaataaaabaahaaaafzaawaapaaaaaarazalqhobgzacazasauaaaaaujafowabywlaagaaadaaatamaaagnpmaeaaaaahmmxapanaraagsxoutbaaaauaqamlazaaaaaaaazaalnsacxltaavaaxpldaqqhapasmalaasutapuasaaatuloaaadaizmaaaaaqqyalyopwakaayhvyaaaczjeauavauxypyenmaaqiaaqiaahuaaakaauja
