Лаборатория PoliCTF 2012 - GrabBag [200]

, 19 ноября 2012

Mmhhh that's a strange way to display a number using a binary representation...
(Submit as upper case hex encoded numbers, with rightmost green led being the MSB. Without leading 0x)

Attachment:4e6ea2210658985.tbz2.gpg (password: d2c29c95d6d7c4918596197aefa870f20f1b299c)

The photos of breadboard with circuit prototype were inside encrypted archive.

Later one photo was given as a hint: gb200.jpg
After that, organizers gave one more hint with integrated circuit datasheet (in Russian!!!): chip.pdf
This task was downgraded to 180 points after this hint.

From this datasheet I've got that used IC is КМ155ИД1 (analogue of 74141) – BCD-to-Decimal decoder IC with high voltage transistor outputs. 

Knowing the inputs and outputs pins, I've made truth tables (0=Low, 1=High).
Four inputs bits as binary are converted to one decimal output code.
Inputs pins are 3, 6, 7, 4 – A, B, C, D respectively.

IC 1:
inputs:         output:
4 7 6 3
0 0 0 0   =>  0

IC 2:
inputs:         output:
4 7 6 3
0 1 1 0   =>  6

IC 3:
inputs:         output:
4 7 6 3
1 0 0 1  =>  9

Output pins (0 on IC1, 6 on IC2, and 9 on IC3) are active with high level (1), and all other pins are off, i. e. with low level (0).

Here is the picture with traced inputs and outputs: result picture

As said in the task, I've set the green leds as MSB and got binary representation:
11101100 11100000 00000001

By converting to hex without leading 0x we get a flag.
The flag: ECE001

1 комментарий:

  1. ChasTume
       #   19:07, 24 мая 2017
    Pharm Support Group Buy Cialis Cats Amoxil Buy Tadacip 20 Mg Cod Pharmacy Online Cialis On Line Amoxicilline Clavulanate Potassium Tablets Amoxicillin Buy Rx Cheapest Prozac Price For Zithromax Cialis Costo En Pesos Cialis Online Prices Tomar Levitra Cialis 20mg Lilly Kaufen Buy Viagra Online Usa List Legitimate Online Pharmacies Can Cephalexin Raise Blood Sugar Zoloft 100mg Levitra Racconti Cialis Online Tadalafil Cheap Cialis No Rx Viagra Levitra Cialis Vergleich Levitra Sotto Lingua Online Lasix Cheap Priligy 30 Mg Dosis Flagyl 500 Order Kamagra Oral Jelly Propecia Risquez Cialis Super Active Difference Cialis Online Prices Wich Is Stronger Cipro And Amoxicillin Kamagra Autorise En France Implicane Online Levitra Vardenafil Online Cialis Vendita Generico Buy Generic Xenical Propecia Algarve Propecia Work On The Temples ?Tadalafil Finasteride 5 Mg For Sale Fluoxetine 40mg Over Night Best Cialis Online Propecia 180 Day Cialis Per Giovani Mail Order Cialis Amoxil 875 Order Worldwide Acticin Tablets Legally Viagra Pill Vente Viagra Livraison Gratuite Pharmacy Canada Cialis Buy Online Cialis Mail Order Finasteride Mastercard Cialis Originale Vibramycin Online Cheap El Cialis Cuanto Cuesta Bad credit loans are not uncommon these days.S. Ask Our Dedicated Team Our Customer Services Representatives will reply to your emails promptly between am and pm Monday to Friday The amount of times you are paid monthly weekly fortnight The great news is theres credit checks involved with your application online however it is not as rigorous as high street banks. cash advance Patrick AZ You Can Trust Forget the slow banks and USA statelicensed direct lender I will be referring everyone to Mr.Propecia Scalp Folliculitis Buy Isotane Uroxatral Xenical Price Sildenafil Generic Buy Viagra Taiwan 49 Que Es El Viagra Buy Zoloft Uk Purchase Provera Abnormal Menstruation With Free Shipping Nombre Generico Del Viagra Sildenafil Generic Provera 5mg Discount Best Website Cod Only Cephalexin Alternative For Dogs Where To Buy Dapoxetine Women Take Kamagra Flagyl Online In Uk Buy Prednisone Without Rx Cialis 2 5 Propecia Recalcine Purchase Cheap Clomid Cialis Kosten Schweiz Viagra Overnight Best Price Viagra Cost Buy Discount Secure Provera Real No Prior Script Side Effects Keflex Second Day Buy Cheap Cialis On Line Propecia Apotheke Online Vendo Viagra En Barcelona Espana Mail Order Viagra Canadian Synthroid Without A Script Achat Viagra Site Us En Ligne Canada Purchase Xenical Order Cialis Professional Generic Quality And Viagra Order Cialis Pills Canadian Pharcharmy Online Viagra accutane online canada no prescription Kamagra Forum Canadian Health Care Shop Propecia 1mgacheter Propecia France Buy Generic Propranolol Online Cialis Prix De Vente Propecia Monedas Viagra Prices Generique Sildenafil 40 Mg Pharmacyrxone Buy Cheap Generic Kamagra Cialis 5mg Dosierung Erfahrungen Achat Levitra En France Brand Zoloft Online No Rx Dog Cephalexin Priligy Israel Buy Cytotec Lasix Deutschland Acheter Levitra Ordonnance Cialis 20mg Price Cheap 5mg Cialis Cialis Free Offer How To Get Lasix Free Shipping Levaquin Medicine Online Overseas Viagra Rezeptpflichtig Holland Buy Zoloft Propecia Verschreiben Cialis Alle Erbe Naturale Kamagra Oral Jelly Kamagra Oral Jelly Hannover Achat Generique Cialis Cheap Kamagra No Rx Canadiandrugs Propecia Muskeln Fast Delivery Cialis Is Cephalexin Safe When Pregnant Cuanto Cuesta La Viagra En La Farmacia Order Viagra Mail Order Amoxicillin Mexico Kamagra With Alcohol Order Zoloft Achat Xenical Pas Cher

Авторизуйтесь, что бы оставить комментарий