Crypto Challenges – Cohesion Writeup

These are the writeups for Cryptography Challenges of the Cohesion CTF by IEEE NCU.

1. Warm-Up -1

So, in this challenge, we simply had to search fish cipher as given in the description and we would find dead fish cipher and after decoding it we will get the flag. cohesion. ctf{D34df1sh_1s_4wes0m3}

2. Warm-Up -2

As we can see here, in the challenge description there is mentioned some kind of a base so after looking on the internet you will find base 91. After decoding it you will get your flag. cohesion.ctf{B4se_91_1s_Lub}

3. Warm-Up -3

Here there is no hint given in the above challenge but if you download the attachment and see the ciphertext you will get to know that it is Malboge Language which is an esoteric language. After decoding it you will find the flag. cohesion.ctf{M4lb0g3_1s_c00l}

4. Basic Ciphers

In this challenge, the description says that the knowledge of some basic ciphers would be useful so after opening the file you will find out the text is encrypted in reversef*ck language, and then in base64 after decoding both you will get the flag. cohesion.ctf{N1c3_K33p_Going_Buddy}

5. Weird Sound

Here a .wav file was given as a part of the challenge when you listen to that it is a dual-tone cipher so to decode it use a DTMF decoder after decoding through this use SMS phone tap cipher to decode the message.

After decoding through DTMF decoder you will get 3 8 6 333 0 8 666 66 33 7777 0 2 777 33 0 333 88 66.

And after decoding this you will get the flag

Wrapping this around the flag format will give you the answer. cohesion.ctf{DTMFTONESAREFUN}

6. What the hell is this?

As we could see in the challenge description there could be something related to (15,3) so after running through a few ciphers you would come across railfence cipher and after decoding the ciphertext with the key(15,3) you will get the flag –> ieeencu.ctf{Y0u_4r3_l33t}

7. Decode This

So here nothing is mentioned in the description, so lets look at the image.

After seeing this image you could clearly see some sign language is used on the box so try to decode it. After some time of googling you would get to know that this is a pigpen cipher and after decoding it you will get the flag.

Wrapping this text would give you the flag. cohesion.ctf{pigpenisfun}

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