Cipher

A stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream ( keystream ).

As with other attacks in cryptography, stream cipher attacks can be certificational, meaning they are not necessarily practical ways to break the cipher but indicate that the cipher might have other weaknesses.

During the Crimean War of the 1850s, Babbage broke Vigenère's autokey cipher as well as the much weaker cipher that is called Vigenère cipher today. citation His discovery was kept a military secret, and was not published.

If the cipher operates on single letters, it is termed a simple substitution cipher; a cipher that operates on larger groups of letters is termed polygraphic.

This container can optionally support digital rights management (DRM) using a combination of elliptic curve cryptography key exchange, DES block cipher, a custom block cipher, RC4 stream cipher and the SHA-1 hashing function.

The Union deployed a cipher system centered on a device called the signal or cipher disk.

An ROT13 cipher is a letter substitution cipher that replaces the 13th letter of text for encryption purposes.

Development of Japanese cipher machines Overview The Japanese Navy did not cooperate with the Army in pre-war cipher machine development, and that lack of cooperation continued into World War II.

However, this cipher is not a machine cipher and as such is not readily suitable for telecommunications. citation Baudot invented his original code in 1870 and patented it in 1874.

In a polyalphabetic cipher, multiple cipher alphabets are used.

Linear approximations for S-boxes then must be combined with the cipher's other actions, such as permutation and key mixing, to arrive at linear approximations for the entire cipher.

OFB-mode and CTR mode are block modes that turn a block cipher into a stream cipher.

Optimization of the cipher On systems with 32-bit or larger words, it is possible to speed up execution of this cipher by combining the SubBytes and ShiftRows steps with the MixColumns step by transforming them into a sequence of table lookups.

Securely using a secure synchronous stream cipher requires that one never reuse the same keystream twice; that generally means a different nonce or key must be supplied to each invocation of the cipher.

Side-channel attacks Side-channel attacks do not attack the underlying cipher, and thus are not related to cipher security in the usually discussed context, though they may be important in practice.

Similar poor indicator systems allowed the British to identify depths that led to the diagnosis of the Lorenz SZ40/42 cipher system, and the comprehensive breaking of its messages without the cryptanalysts seeing the cipher machine.

Since encryption of each digit is dependent on the current state of the cipher, it is also known as state cipher.

Standard model main Informally, a block cipher is secure in the standard model if an attacker cannot tell the difference between the block cipher (equipped with a random key) and a random permutation.

The concept of zero (which was also called "cipher"), which is now common knowledge, was alien to medieval Europe, so confusing and ambiguous to common Europeans that in arguments people would say "talk clearly and not so far fetched as a cipher".

The Vigenère cipher uses a Caesar cipher with a different shift at each position in the text; the value of the shift is defined using a repeating keyword.