HackThisSite - Basic Level 6 - Weak Encryption

In this challenge, Sam has encrypted his password using a well-known and publicly available encryption method. Your task is to figure out which encryption system Sam used.

To get started, enter any arbitrary text, such as the word world, and hit the encrypt button:

The output is:

As you can see, the word wptoh is the encrypted form (ciphertext) of the plaintext world:

  world       →     wptoh
plaintext        ciphertext

This encryption method is a classical substitution cipher in which each character is shifted forward by an increasing offset based on its position in the string. For example, the first character is shifted by 0, the second by 1, the third by 2, and so on. However, in this scenario, the shifts are applied using the ASCII values of the characters.

This can be illustrated as follows:

And that’s essentially how the plaintext world becomes wptoh.

You can apply the same principle in reverse to decrypt Sam’s encrypted password4746j8:=, that is, by subtracting the positional shift from each character’s ASCII value. This is what I mean:

After reversing the transformation, you recover Sam’s original plaintext password: 4623f346

Security Recommendations

Simple ciphers can be broken very easily once someone understands the pattern. Passwords should never be encrypted in a way that can be reversed, instead, they should be stored using strong password hashing methods like bcrypt, Argon2, or PBKDF2, which are built specifically to protect passwords. On top of that, adding randomness (a salt) to the encryption process makes each password unique and much harder for attackers to crack, even if two users choose the same password.

It’s also important to use trusted, well-known security libraries rather than writing your own encryption code.