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Although ciphers can be confusion-only (substitution cipher, one-time pad) or diffusion-only (transposition cipher), any "reasonable" block cipher uses both confusion and diffusion. [2] These concepts are also important in the design of cryptographic hash functions , and pseudorandom number generators , where decorrelation of the generated ...
In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext, thus ensuring Shannon's property of confusion.
The propagating cipher block chaining [25] or plaintext cipher-block chaining [26] mode was designed to cause small changes in the ciphertext to propagate indefinitely when decrypting, as well as when encrypting. In PCBC mode, each block of plaintext is XORed with both the previous plaintext block and the previous ciphertext block before being ...
The reason for confusion is exactly the same as for diffusion: changing one bit of the key changes several of the round keys, and every change in every round key diffuses over all the bits, changing the ciphertext in a very complex manner.
For example, (a) your original text can be restored and modified to limit the hash functions of hash tables to a subset of these functions that (1) use a key and (2) provide some confusion with respect to the said key. Another alternative is to (b) put the word "sometimes" when describing the confusion and non-keyed hash functions.
An example of a 64-bit "expansion" P-box which spreads the input S-boxes to as many output S-boxes as possible. In block ciphers based on substitution-permutation network , the P-boxes, together with the "substitution" S-boxes are used to make the relation between the plaintext and the ciphertext difficult to understand (see Shannon's Confusion ...
The concept of product ciphers is due to Claude Shannon, who presented the idea in his foundational paper, Communication Theory of Secrecy Systems. A particular product cipher design where all the constituting transformation functions have the same structure is called an iterative cipher with the term "rounds" applied to the functions ...
The trifid cipher is a classical cipher invented by Félix Delastelle and described in 1902. [1] Extending the principles of Delastelle's earlier bifid cipher, it combines the techniques of fractionation and transposition to achieve a certain amount of confusion and diffusion: each letter of the ciphertext depends on three letters of the plaintext and up to three letters of the key.