Demonstration of how security through obscurity fails to work. Example transformation
I need to demonstrate that security through obscurity fails twice in the following scenario.



I've a secret KEY.  

<p><i>User A</i> gets   <b>MessageX</b> = SecretTransformation(KEY, SecretValue1);</p>
<p><i>User B</i> gets   <b>MessageY</b> = SecretTransformation(KEY, SecretValue2);</p>

Now, Security through obscurity is in contrast with principle of open design and shannon's maxim. We also know that this security will fail as soon as an attacker manages to retrieve one of the "secrets"

what in addition it think can be demonstrated, is that:

if an attacker manages to retrieve, **MessageX** and **MessageY** without knowing any secret he can perform some cryptanalysis attack and retrieve the **KEY** or understand the **SecretTransformation** functioning.


I hope I've explained myself i need to be pointed out to some example like the one time pad, where if you XOR with the key more then one message you can XOR back and retrieve the secret.

Thank you!
Demonstration of how security through obscurity fails to work. Example transformation
===

I need to demonstrate that security through obscurity fails twice in the following scenario.



I've a secret KEY.  

<p><i>User A</i> gets   <b>MessageX</b> = SecretTransformation(KEY, SecretValue1);</p>
<p><i>User B</i> gets   <b>MessageY</b> = SecretTransformation(KEY, SecretValue2);</p>

Now, Security through obscurity is in contrast with principle of open design and shannon's maxim. We also know that this security will fail as soon as an attacker manages to retrieve one of the "secrets"

what in addition it think can be demonstrated, is that:

if an attacker manages to retrieve, **MessageX** and **MessageY** without knowing any secret he can perform some cryptanalysis attack and retrieve the **KEY** or understand the **SecretTransformation** functioning.


I hope I've explained myself i need to be pointed out to some example like the one time pad, where if you XOR with the key more then one message you can XOR back and retrieve the secret.

Thank you!