□ Claude Shannon presented the principle of confusion and diffusion.
□ Diffusion(확산) principle
○ Diffusion complicates a ciphertext's statistical property.
* If statistical property of a ciphertext is found, the key can be found.
○ Diffusion principle can be implemented as Permutation(=Transposition)(전치) algorithm.
□ Confusion(혼돈) principle
○ Confusion complicates the relation between key and ciphertext(=The key drastically changes the ciphertext).
* Even if same key is used for different plaintexts, the each pattern of the ciphertext is completely different.
* Even if only one bit of the key is changed, the ciphertext is changed to a completely different pattern.
* Even If statistical property of a ciphertext is found, It is still difficult to find the key.
○ Confusion principle can be implemented as Substitution(치환) algorithm.