Hack This Site (HTS) Basic 6

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 publicly available and can be accessed with this form."

This mission is fairly simple but is completed using an ascii chart and notepad. By entering something like 00000 into the encrypt field we notice that the returned sting is 01234. This tells us that the encryption scheme is to add its place value in the string to itself. As in computing we start from 0 the first characters place value is 0 and the value is not changed. The second 0's place value is 1 and so 1 is added to 0 to make 1, and so fourth. This also applies to characters. The string aaaaa gets changed to abcde. This is because ascii characters are just the character representation of numerical values. So now we know what the encryption scheme is we now need to decrypt. This simply requires reversing the encryptino scheme; minus the place value instead of adding it.

The string I have been given to decrypt is 41die;79. By implementing the decryption scheme the string value i now get is: 40bfa612