Cryptography/Basic Design Principles

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Good ciphers often attempt to have the following traits.

Kerckhoffs's principle[edit | edit source]

Kerckhoffs's principle, also called Kerckhoffs's law:

A cryptosystem should be secure even if everything about the system, except the key, is public knowledge.

In the words of Claude Shannon, "The enemy knows the system." (Shannon's maxim).


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To do:
Say something about "security through obscurity" here. Perhaps also something about Kerckhoff's other 5 principles.


Diffusion[edit | edit source]

Having good diffusion means that making a small change in the plain text should ideally cause as much as possible of cipher text to have a fifty percent possibility of change.

For example a Caesar cipher has almost no diffusion while a block cypher may contain lots of it.

Confusion[edit | edit source]

For good confusion the relationship between the cypher text and the plain text should be as complex as possible.

Further reading[edit | edit source]