Cryptography diffusion and obfuscation memo

Diffusion and confusion are C. e. the two basic methods proposed by Shannon to design the password system are aimed at resisting the competitor's statistical analysis on the password system. in the design of the group password, the full use of diffusion and confusion can effectively resist the opponent from the ciphertext statistical characteristics to speculate on the plaintext or key. diffusion and confusion are the basis of the design of modern group passwords.

So-called ExpansionHash means that each bit in the plain text affects many bits in the ciphertext, or that each bit in the ciphertext is affected by many bits in the plain text.. In this way, the statistical characteristics of plaintext can be concealed. of course, the ideal situation is to make every bit in the plain text affect all bits in the ciphertext, or make every bit in the ciphertext affected by all bits in the plain text.

The so-calledObfuscation is to make the statistical relationship between the ciphertext and the key as complex as possible.So that the opponent cannot speculate on the key even if he obtains some statistical features about the ciphertext. the obfuscation effect can be achieved through complex nonlinear substitution transformation, while the obfuscation effect obtained by simple linear substitution transformation is not ideal. you can use the "kneading dough" to vividly represent diffusion and confusion. of course, this "kneading dough" process should be reversible.Product and iteration help achieve diffusion and confusion. Some simple key-controlled password transformations can be selected to achieve better diffusion and obfuscation effects through product and iteration.