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In cryptography, the Tiny Encryption Algorithm (TEA) is a block cipher notable for its simplicity of description and implementation, typically a few lines of code.It was designed by David Wheeler and Roger Needham of the Cambridge Computer Laboratory; it was first presented at the Fast Software Encryption workshop in Leuven in 1994, and first published in the proceedings of that workshop.
Decoding a general linear code, however, is known to be NP-hard, [3] however, and all of the above-mentioned methods have exponential running time. In 2008, Bernstein, Lange, and Peters [ 5 ] described a practical attack on the original McEliece cryptosystem, using the information set decoding method by Stern. [ 11 ]
The XOR cipher is often used in computer malware to make reverse engineering more difficult. If the key is random and is at least as long as the message, the XOR cipher is much more secure than when there is key repetition within a message. [4] When the keystream is generated by a pseudo-random number generator, the result is a stream cipher.
In some cases the terms codes and ciphers are used synonymously with substitution and transposition, respectively. Historically, cryptography was split into a dichotomy of codes and ciphers, while coding had its own terminology analogous to that of ciphers: "encoding, codetext, decoding" and so on.
In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code, or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet .
The most obvious and, in principle at least, simplest way of cracking a code is to steal the codebook through bribery, burglary, or raiding parties — procedures sometimes glorified by the phrase "practical cryptography" — and this is a weakness for both codes and ciphers, though codebooks are generally larger and used longer than cipher ...
Stream ciphers, in contrast to the 'block' type, create an arbitrarily long stream of key material, which is combined with the plaintext bit-by-bit or character-by-character, somewhat like the one-time pad. In a stream cipher, the output stream is created based on a hidden internal state that changes as the cipher operates.
The Rail Fence cipher is a form of transposition cipher that gets its name from the way in which it is encoded. In the rail fence cipher, the plaintext is written downward and diagonally on successive "rails" of an imaginary fence, then moves up when it gets to the bottom. The message is then read off in rows.