- Level: Basic::6
- URL: http://www.hackthissite.org/missions/basic/6/
- Exercise: An encryption system has been set up, which uses an unknown algorithm to change the text given. Requirements: Persistence, some general cryptography knowledge. Network Security Sam has encrypted his password. The encryption system is publically available and can be accessed with this form. Please enter a string to have it encrypted. You have recovered his encrypted password. It is:a7e34:l=. Decrypt the password and enter it below to advance to the next level.
We have to understand how the encryption works. Enter some letters: a, b, c, ... and some numbers: 1, 2, 3. You will notice that the increment seems to be the same. By using an ASCII conversion table (http://www.asciitable.com/), you will notice that we have following scheme:
- Each position is converted in ASCII number.
- Each position is then transformed with: +0 for the first position, +1 for the second one, +2 for the third one, etc.
- New ASCII after transform are then converted into characters.
To get the solution, we apply the reverse scheme. Here is the scheme:
|Result after transform||97||54||99||48||48||53||102||54|
|ASCII (after transform)||a||6||c||0||0||5||f||6|