CryptoGolf

Challenge Description:

Description: 
nc challs.m0lecon.it 11000

Foreword

CryptoGolf was the first challenge of a series of very fun and interesting cryptography challenges that my teammates and I solved in m0leconCTF World Quals where we placed 5th globally in the Open Division, qualifying for the Grand Finals in Turin, Italy.

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Analysis Incarnate 2

This is a proof of Euler’s Identity using the Taylor Series.

a

We can write $ie^{i\phi}$ as the Taylor Series expansion.

b

Let’s visualize this sum. It helps to write out all your terms because you know that the powers of i are going to alternate between 1,-1,i,and -i.

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Analysis Incarnate

This is a quick proof of Euler’s formula without the use of the Taylor Series.

a

Even with the imaginary number i, this equation is differentiable, so we can take the derivative of :

b

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Access=0000

This is a writeup for a crypto challenge in RACTF 2020, where we placed 6th.

Challenge Description:

Challenge instance ready at 95.216.233.106:57735

We found a strange service, it looks like you can generate an access token for the network service, but you shouldn't be able to read the flag... We think.

Solving :

We are given access.py. Lets take a look the server file to see what the program does.

From the top, we see that get_flag:

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Really Smart Acronym

Challenge Description:

Man, oracles are weird.

nc challenges1.hexionteam.com 5000

Solving :

​Really Smart Acronym, of course, is RSA. Looking at the code, it uses PyCrypto to generate a RSA key to encrypt the flag. You also get one encryption and 1024 decrypts, but you only get the last bit of the decrypts. At first we thought it could be Franklin-Reiter related-message attack, but there is not enough information for that.

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