BSidesSF 2026 CTF — Strike a coord Writeup

Introduction:

Well, as someone who loves OSINT, its very sad that i rarly see challenges with that category, so when i saw this challenge i was very happy and i said that i MUST make a writeup about it.

Breakdown:

When you open the link you can see the page as the screenshot above, piano keys with a list of 14 pictures, when you click each one of them the piano keys colors/texture change accordingly, each picture have a tiny part covered, our goal is to find the original location and look at the covered part, then click the designated key.

Solution:

For each picture we need to identify the location, then search it on google maps, then click on the button below (you can find it bottom right corner) to view the street view and find the exact frame, I also suggest to always use satellite view, it will help you identify the area easier.

lets start solving, picture by picture.

Picture 1:

This one is easy, on the left side you can clearly read the name of the location (Beethoven-Haus Bonn), the Ukrainian flag is just a mislead.

Exact Location, now we just need to click on the color of the sign (Blue / B4).

Picture 2:

This one is easy too, Location is (Gangnamdol Haus), but for this one, the same exact frame cant be found, but you can still find what you need.

Location, as you can see the people and the angle is different, anyways, now just click the letter visible on that wall (K / E4).

Picture 3:

This is a well-known tourist attraction, in case you couldn't identify it (don't worry i couldn't too) you can just drop the picture to google search and you can find the name of the building (Teatro Colón), now we just need to find the exact angle.

Exact Location, now just click at the color of that hidden umbrella (Yellow / G4).

Picture 4:

The word samba is clearly visible on the right side, so now we know its in samba, if you zoom into the sign over the green door we can read “Museu” but the rest is covered by wires, lets take a guess and try searching (Samba Museum) on google maps.

Exact Location, now just press the color of that covered sign (Brown / F#4).

Picture 5:

The only readable thing there is “siam properties” which is on a truck, by searching it you can now know that this company exists in Pattaya, which means the picture is in Pattaya, but where exactly?

In the picture we can see a palm tree where the cameraman stands, taking a quick look on the satellite view of the city we can see that palm trees exists only on the beach road side, we can also see trees on the other side of the street and a huge clue is the round building, lets investigate these clues.

This place looks like what we are looking for.

1. Palm trees.
2. Wall of trees on the other side.
3. Round building.
4. The same tall building in the background.

Exact Location, now press what you can read on the covered sign (Hz / E4).

Picture 6:

Nothing to read, but that building on the right looks recognizable, google search by image gives us the result (Abbey Road Crosswalk), what makes this picture easier to find is that Abbey Road Crosswalk is iconic by a late 60s album cover, the place in the picture is an intersection between 3 roads, one of them is Abbey Road.

Exact Location, now just press the direction and the number covered in the picture (NW8 / B4).

Picture 7:

The only thing we can read here is “SUN S…”, using google image search we can find this Reddit post, the guy says a major leads (Sun Studio in Memphis), that's our target!.

Exact Location, now press the fruit covered in the picture (Banana / A4).

Picture 8:

We can read “PANTAGES PARKING”, by searching google maps, we can find (Hollywood Pantages Theatre), so this picture must be somewhere around it, lets take the leads, two buildings, the near one is round the far one is rectangle, stars on the pathway.

This looks like our goal.

1. The same 2 buildings.
2. Stars on the pathway
3. The wall is litterly labeled as (Public Art “Hollywood Jazz”).

Exact Location, now just press the color of the man`s clothes (Blue / F#4).

Picture 9:

The only readable word here is “SOCIETAS”, searching that gives no results, if we try image search, we can see a picture from a different angle with the description (Antico Martini) so now we know the name of the place is antico martini.

We can clearly identify that this is our location.

Exact Location, there is a roman number there, just convert it then press it on the piano (MDCCXCII / 1792 / E4).

Picture 10:

We can clearly see this is a tourist attraction, alot of people, alot of torism buses, we can read “Vienna” on one of the buses, we can know its in vienna, but where exactly?.

Here we have 2 methods to find the exact location

1. We can open the map and lool between all of the tourist attractions there till we find this one.
2. Or we can just ask google image search which will say (Vienna State Opera).

Exact Location, now just press that shape on the piano (Star / G4).

Picture 11:

The only readable thing here is “Backstage”, and when you search it on google maps you will get ton of results around the world, but look at this at the back.

This looks like a tourist attraction, if we google image search it we can know that it`s name is (Nordic Museum), now we can just search it google maps and look around it.

Exact Location, now just press the hidden letters on the piano (ABBA / F#4).

Picture 12:

This looks like an interior of a museum, we can read “Hall of Fame” very clearly, searching it on google maps gives you 2 wrong results, we can read “Rock” at the top left corner, search “Rock Hall of Fame on google maps gives us the result (Rock & Roll Hall of Fame) and that's very suspicious, but how can we make sure its the same?, looking at street view map we can see ton of blue lines and dots, which will be very hard to look between.

We can search the original message on google image search which confirms that Rock & Roll Hall of Fame is actually the answer and it also shows us the same hall from another angle and the answer is visible.

But what if we want to find the exact frame?, here we can see the floors, and as we can see, the hall of fame is at the 3rd floor.

But no matter how hard we try to press on that area at google street view we cant get there, we can only find this hall which looks like it but different showcase.

If you look closely at the right of your screen you can find these buttons:

Here, if we simply just press at 3, we can get the hall of fame and find our Exact Location, now just press the hidden symbol (Key / D#4).

Picture 13:

We can read 2 major leads “Tony Roma`s & Hard Rock Cafe”, and from the Japanese letter all around we can know its in Japan, if we do a little search we can see that both of them have a lot of branches around Japan, we just need to find where both of them exist next to each other.

We can search “tony romas and hard rock cafe japan”, google maps will show us the pins for both of them at the same time, and will limit it to branches that are near to each other, anyways we can now easily identify our target.

Exact Location, now just press the animal on the piano (Cat / F4).

Picture 14 (Last):

In the background we can see “Sydney Harbour Bridge” & “Sydney Opera House”, from the picture we can see a glass roof that can be easily seen in the satellite view, and we can also see that the camera man is standing near from the water and there is a big building to his right.

We can keep going far from the opera house little by little till we find this, which looks exactly as what we need.

Exact Location, now just press the color of the shirt on the piano (Orange / B4).

Final Steps & Conclusion:

Now after we found all of the pictures` location the final note looks like this (B4 E4 G4 F#4 E4 B4 A4 F#4 E4 G4 F#4 D#4 F4 B4).

Now if we press “Check” we can hear the note which is harry potter`s theme and this picture will show up.

The flag is clearly visible, congratulations! you did it! you are a geowizard.

CTF{yer_a_geowizard}

The source code of the challenge can be found here.