## PicoCTF 2017 – Hex2Raw

Another day, another challenge…

Today’s challenge we will be solving the Hex2Raw challenge in the PicoCTF.

Let’s start.

Clicking on the challenge we see the following:

OK. With this challenge we see that we need to print unprintable characters from the following location.

Let’s see what the hints give us.

Clicking on the hints we see:

OK. We can see that Google has easy techniques to do this.

Let’s go to the command line and see what we can do.

After logging in and going to the directory we see the following:

Running the hex2raw application we see:

I pressed Ctrl + C to end the program.

OK. We are given raw input and we need to convert it to hexadecimal character.

Doing a Google search we noticed that we can use Python to get our desired output.

How would we do this?

With the decode function!

Explaining the screenshot below we’re invoking the python interpreter the -c designated that we’re using a command. We’re printing the raw form, and using the decode function designated that we wanted to decode with the hexadecimal system. We’re going to pipe the output to the hex2raw program.

Doing this we see the flag, and acquired 20 points!

## PicoCTF 2017 – computeRSA

Another day, another challenge.

Today’s blog post will explore solving the “computeRSA” challenge in the PicoCTF challenge.

Let’s get started.

Clicking on the challenge we see the following:

OK we need do a calculation for the RSA algorithm. Since we have the encrypted number, then we need to do the decryption.

Let’s look at the hints.

We have the decrypted formula.

So the formula: (150815) ^ 1941 mod 435979

Let’s go to Google and use a python interpreter to find the decrypted number.

Going to the following link we’re presented with the interpreter.

Entering the formula in the interpreter we get the following:

Entering this number as the flag we’ve acquired 50 points!

## PicoCTF 2017 – looooong

Another day, another challenge…

Today’s blog post is to solve the looooong challenge from PicoCTF.

After login and opening the challenge we see the following:

We need to see how fast our typing speed.

Clicking on the hints we see the following:

Going to the command line and connecting to the server we get the following:

We see that we have thirty seconds to enter the following 533 r’s an a single 3.

The hint stated we should try using python.

I can’t say enough about Python. It’s a GREAT first language for beginners to learn. TheNewBoston on YouTube has a good tutorial on Python.

Anyway, back to the challenge – going to Google and typing “Python interpreter online” we’re presented with the following here.

Python has a great way of printing characters multiple times with the following:

print ‘a’ * 399

This will print a 399 times.

I have to admit I had to do this challenge a couple of times as I was slow.

I’m going to add the screenshots of the challenge I was able to solve.

Going to the link I provided I typed – print ‘v’ * 538 – I was presented with:

Copying the v’s and going back to our challenge, if we right click in the command line and select paste from browser we get the following:

Entering the v’s and adding the single 1 at the end and pressing OK I received the following:

We received the flag and acquired 20 points!

Word of advice – have AT LEAST two window open. 1 window with the challenge, the second window of the python interpreter.