UMDCTF — Easy Challenge Write ups

Lo Yen Xuan

5 min readApr 19, 2021

Steganography: Testudo’s Pizza

This was the image for the challenge:

I find this cheat sheet super helpful: https://fareedfauzi.gitbook.io/ctf-checklist-for-beginner/steganography

Solution:

strings hiddenmsg.jpg | grep UMDCTF                                            \f0\fs24 \cf0 \'93UMDCTF-{W3_ar3_th3_b3st_P1ZZ3r1a}\'94}

Flag obtained: UMDCTF-{W3_ar3_th3_b3st_P1ZZ3r1a}

Cryptography — Art Class

This is an example of symbols cipher, list of symbols cipher can be found here: https://www.dcode.fr/symbols-ciphers

Solution:

This is a Navy Signals Code. Simply decrypt it using the link above and you will get the flag.

Flag obtained: UMDCTF-{F1AG_0F_7LA9S}

Crytography — Celebration

Using this link again, https://www.dcode.fr/symbols-ciphers, we know that this is form of symbols cipher is called the “Dancing Men Cipher”.

Solution:

Flag obtained: UMDCTF-{yo_ITS_A_PARTYYY}

OSINT — Traveling

This was they image they gave us:

Solution:

Using this picture, I conducted an reverse image search on google with the keyword “Pine Street”.

I went through the pictures and looked around the streets on Google Earth on Pine Street in New York, but the design of the lamppost didn’t match. (New York’s lamppost was black and white while the lamppost in the picture is green.) However, the design of the “one-way” signboard matched perfectly. My next targeted location was at Pine Street, St. Louis in MO, USA. The “one-way” signboard matched again, but there was no sign of the building anywhere. I tried to reverse image search again with the keyword “pine”, and this time, I got something interesting.

I’m pretty sure this building is the same as the building of the picture of the challenge. I searched again in alamy, and I found this:

The building next to it has a name : blend. This picture was also captioned “Pine Street San Fransisco View”. So now, I know that its in Pine Street, San Fransisco, and its next to a building named “blend”. Just search it on Google Earth and we found it!

The building is called “555 California Street”. More information can be found here: https://en.wikipedia.org/wiki/555_California_Street

Final flag: UMDCTF-{555 California Street}

OSINT — Nikolai 1

Solution:

By using a simple advanced search in Google, (https://support.google.com/websearch/answer/35890?co=GENIE.Platform%3DDesktop&hl=en), I was able to find out Nikolai’s twitter account.

Nikolai’s twitter link: https://twitter.com/mercatornikolai?s=11

We can see that he has an account in OSM (openstreetmap.org) and he once put the link to his OSM account in his bio but he then removed it. Therefore, https://www.quora.com/How-do-I-view-someone-else-s-old-Twitter-bio , and by using the waybackmachine, we were able to view the link! https://web.archive.org/web/20210325030255/https://twitter.com/mercatornikolai

We got the flag!

Flag obtained: UMDCTF-{4_m4pp3r5_p4r4d153}

OSINT — Nikolai 2

Solution:

By looking through Nikolai’s diary his OSM account and his twitter feeds, we were able to gather some information.

By a reverse image search on Google, I was able to find this:

This is Nikolai’s commits for OSM in the past 30 days:

Nikolai’s Diary in OSM:

Settling Down For a Bit
Posted by NikolaiM99 on 11 April 2021 in English (English).
After riding the Greyhound for a day I decided on a city I want to stay in for a bit. I’m sure I mentioned this before but I want to really use this time to enjoy myself, and hiking is a perfect way for me to do that! I went on a small hike today, had to take an Uber there but it wasn’t too bad of a drive (5–7 miles ish). Locals are probably used to seeing this landmark but I had to express my opinion on it…..
Don’t get me wrong, this rock formation does look pretty cool, but I don’t see how it looks like a pair of kissing camels like everyone says. Maybe its just the angle I took the pic at? I’ll probably use some more of my pics on social media just to spice things up, see ya guys later!

Nikolai’s twitter feed:

Nikolai Mercator
Apr 11
Anyone know the difference between a Lodge, Motel, and Hotel? I thought I was staying in a Motel but I guess its also a Lodge…… Some would say this is a shower thought, but I had it on a hike
Nikolai Mercator
Apr 12
The last day or two I’ve exclusively eaten gas station food and domino’s, they are both within walking distance of me so I don’t even have to pay for delivery

In Colorado Springs, there’s a place with a lot of motels and a domino pizza nearby. (38.89371,-104.81887)