UDSM CYBER SECURITY CHALLENGES WRITEUPS

refer: https://udsm-cyberhub.tech/challenges

1. CRYPTOGRAPHY CHALLENGES

a. decode me
description: Can you decode the string and get flag

there is a file given in the challenge , after downloading and opening it, i found 'VURTTXtfX19CQVNFNjRfKmVuY29uZGluZypfX199Cg==' which seems to be base 64
i wrote the command as shown below and got the flag
┌─[alexius@alexius-hpprobook4430s]─[~/Downloads]
└──╼ $cat cipher.txt | base64 --decode
UDSM{_ _ _ BASE64_* enconding*___}

flag:UDSM{_ _ _ BASE64_* enconding*___}

b.thirteen-times
description: rotate that cipher.txt string to get your reward

there is a file given in the challenge , after downloading and opening it, i found 'HQFZ{ebg_Gu1eg33a_vf_Na0gu3e_raP0q1at}' then from the description, i rotated the cipher 13 times (ROT13) using an online tool : https://gchq.github.io/CyberChef/

flag; UDSM{rot_Th1rt33n_is_An0th3r_enC0d1ng}

c. morse
description: decode the cipher.txt to get a flag. Wrap your decoded fllag with UDSM{xxx} before submitting.

i opened the file and found the cipher contains of two symbols (- and .) , cipher: .. ..-. -.-- ----- ..- --. ----- - - .... .---- ... -.-- ----- ..- .-. . --. ----- ----- -.., therefore from the description the cipher seems to be morse code. then i tried to decode it using the same online tool cyberchef and i got the flag.

flag: UDSM{IF_Y0U_G0T_TH1S_Y0URE_G00D}

d. vigenere
description: Can you decode the enc.txt and get the flag

the challenge was attached by a zip containing enc.txt : ELTI{H0GT_DzVoX_O1G3X3Z3_D1LL3K_}and the key.txt: KIBWETA therefore since the challenge is vigenere therefore i decoded it using the same tool and i got the flag

flag: UDSM{D0NT_TrUsT_V1G3N3R3_C1PH3R_}

e. sick doctor

description: We have intercepted these strange messages which we saved in the cipher.txt file. Are you able to help us decipher them?
the file contains a cipher "SLKVUFOOB GSRH RH VMLFTS GVCG GL SVOK DRGS BLFI HFYHGRGFGRLM! TVG XIZXPRM!.

Uozt: FWHN{Hf_Yhg1gFgr0mzo_Xrks3i}" which was substitution cipher as the hint says, i tried different online tools but it didnt work propery, but since i knew substitution contains a lot of algorithims then i tried Atbash ciher decoder and woooow i got the flag.
"HOPEFULLY THIS IS ENOUGH TEXT TO HELP WITH YOUR SUBSTITUTION! GET CRACKIN!.

Flag: UDSM{Su_Bst1tUti0nal_Ciph3r}"

f. keys

description: Help us to find a way to decrypt what is being hidden in this file

the file given contains of a token and a key
key = Q1ddlMD08dedHPoRbTd3RdHgq3s0XKXretIarj4ADFI=
token = gAAAAABiZ8m3gF2FBNooCpit59mvq0pVu9P_W5zaAXnLBI1Z0ghm9FhqB_IHTZxGPVElCUsQV_OpzeWHlRg2dDmmeid-llCHpFwXFBaWzY0j5LDeILpSVvU=

the cipher is fernet and i used my favourate tool https://asecuritysite.com/encryption/ferdecode to decode the cipher and i got it.

flag: UDSM{__kEys_KeYs_k3ySS!!!!!!}

g. rsa 101

description: see if you can turn those factored primes and cipher text into plain text flag!.

given file contains
p = 177529604771775811447794627528898905563608127308618713400260159684003628121897638346581772088147960905570447556763891720452738611287634839201158386379116429397697859892035253074680507674006763427672353958542251411700851999453703543179036524728177137039687762641769500501195739670681098180171316381127270595227
q = 164605327901737124994495240514963132711119880263548875469413634209843421608331532413725908549738247339988511183442179013710866395980475766695666579326675217280967182799100068138408362426253645047678448844920272489814433869044523491025443060926656512153072234650261104282229763306821456650374030627172191797163
c = 8597017218851008583576801905806185130587818490260411862690369905777080071229720959516829073656474975437225573094576293319069131259203963765181834391162333482142524368575836978190931937791651504986155615680437878372517464872539285876838552791831157964677887962486974098531508876917887507074079565218881076487529277349539083007398175486804759715561086540010558152818123077067049267481361668280490076714835497613464066247962321065347243361091242745725212593209312514712727068711242381476024156587636523611686223568570546504638344178467678967575403901560576840131743194481311169704067882482231401216743076246398522274892
e = 65537

i used this online tool https://www.dcode.fr/rsa-cipher and solved the challenge

flag: UDSM{Sh0uLdve_Us3d_Str0Ng_Pr1mes!}

>>That wa all about cryptography challenge, next time i will publish coding exercise and binary exploitation challenge.
>> please subscribe to my youtube channel https://www.youtube.com/watch?v=gJWxR1StbI4 and God bless you all.