MCSC 2019 (open level) A Few Crypto Write Up

Categories CTF

1. R uoOk?(Cryptography)

I found some hints in the question.I know that it use ook cipher.I used online decrypter and got the flag.

flag=MSCS2019{I_ThinK_I_aM_N0t_0K!}

2. 404 not found (Cryptography)

Firstly.I trying to change this text to hex. 

I got this hex

125404121404764041084049740478404105404704049540484404105404954046840410540410040495404117404484048940495404101404109404484048340451404119404654041234045740449404484045040467404834046740477404

I found some hints in questions.So we need to remove 404 from this hex.

I got this following.

125 121 76 108 97 78 105 70 95 84 105 95 68 105 100 95 117 48 89 95 101 109 48 83 51 119 65 123 57 49 48 50 67 83 67 77 

I know this is a decimal numbers and use decimal to ascii conveter.

Now I got the following text.

}yLlaNiF_Ti_Did_u0Y_em0S3wA{9102CSCM

I know this is reverse text.So let reverse this text with online converter.

Bingoo!!

I got the flag.

MCSC2019{Aw3S0me_Y0u_diD_iT_FiNalLy}

3. Old School SMS (Cryptography)

I used foremost tools to extract this jpg file.

foremost hello.jpg

You can view the result in output folder.In the output folder, you will see pdf folder.

Open the pdf file in this folder, I see the following.

I know this is mobile keypad cipher. I used online tool to decode this.

Now,I got the flag.

MCSC2019{ILOVEKEYPADMOBILEPHONE}

Thanks for your time.

Best Regards, KT Yur!ko