# Crypto Challenge

• June 29th, 2002, 03:35 AM
Simon Templer
Crypto Challenge
Ok... I figured I'd go ahead and post a challenge (Hell everyone else is doing it! ;) )

Here we go:

This is a simple encrpytion that uses an encryption key:

Text: t (Lower Case)
Key: D (Upper Case)
--------------------------------
Creates: 0 (That is Zero)

In this case the text and the key was a single character. Ok, now let me show you a key with 2 characters.

Text: t (Lower Case)
Key: D (Upper Case)
Key: @ (The AT Sign)
--------------------------------
Creates: p (Lower case)

Ok here are some hints:

1. Get out an ASCII Table
2. Think Binary

If you do those two things, you will see the pattern!

Have Fun, I will post more clues, or the answer tommorow. :)

Simon Templer
• June 29th, 2002, 05:40 AM
ammo
A simple XOR and double XOR (XORed with the first key then with the second)...

At last I got one ;)

Ammo
• June 29th, 2002, 04:17 PM
Simon Templer
Congrats
Congrats Ammo,

You figured it out!!! :)

I guess that was too easy eh? :confused:

- Simon Templer
• June 29th, 2002, 06:30 PM
rmchokku
Cryptography
Integrity:

Could anyone please tell me the logic behind file integrity checkers(for example md5.exe).What type of logic can be applied while designing tools like that.Do think that i'm asking the code of md5.exe.Hope you won't mistake my words.

Chokks.
• June 30th, 2002, 09:37 AM
darkes
Re: Cryptography
Quote:

Originally posted here by rmchokku
Integrity:

Could anyone please tell me the logic behind file integrity checkers(for example md5.exe).What type of logic can be applied while designing tools like that.Do think that i'm asking the code of md5.exe.Hope you won't mistake my words.

Chokks.

The code for MD5 is freely available (it's in the public domain) - try fourmilab for example, which also gives a brief explanation on what it does. It's basically a hash algorithm that can be used to authenticate a message/file etc. that you have downloaded/transferred.
Not entirely sure what your question was asking, but the point behind this is that it doesn't require any keys or encryption software to be installed on the system that is receiving the data.
The data (message/file etc.) is assumed to be non confidential - so you don't mind if any one else reads it. What it does do is to verify that the copy of the data you have received is the same as the original, so that you know that no one has tampered with the contents of the original data.