I need to demonstrate that security through obscurity fails twice in the following scenario.
I've a secret KEY.
User A gets MessageX = SecretTransformation(KEY, SecretValue1);
User B gets MessageY = SecretTransformation(KEY, SecretValue2);
SecretTransformation() is not a standard cryptographic function.
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.
This is supposed to be true and get stronger with the number of messages the attacker is able to collect. messageX messageY ... messageN 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.
here there is an image for the schema suggested http://s17.postimage.org/mdgij13un/bad_Transformation.png