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Encyclopedia > NewDES
Designer(s): NewDES Robert Scott 1985 120 bits 64 bits 17 A related-key attack succeeds with 232 known plaintexts

In cryptography, NewDES is a symmetric key block cipher. It was created in 1984–1985 by Robert Scott as a potential DES replacement. Despite its name, it is not derived from DES and has a quite different structure. Its intended niche as a DES replacement has now mostly been filled by AES. The algorithm was revised with a modified key schedule in 1996 to counter a related-key attack; this version is sometimes referred to as NewDES-96. In cryptography, the key size (alternatively key length) is a measure of the number of possible keys which can be used in a cipher. ... In modern cryptography, symmetric key ciphers are generally divided into stream ciphers and block ciphers. ... Cryptanalysis (from the Greek kryptÃ³s, hidden, and analÃ½ein, to loosen or to untie) is the study of methods for obtaining the meaning of encrypted information, without access to the secret information which is normally required to do so. ... In cryptography, a related-key attack is any form of cryptanalysis where the attacker can observe the operation of a cipher under several different keys whose values are initially unknown, but where some mathematical relationship connecting the keys is known to the attacker. ... The German Lorenz cipher machine, used in World War II for encryption of very high-level general staff messages Cryptography (or cryptology; derived from Greek ÎºÏÏ…Ï€Ï„ÏŒÏ‚ kryptÃ³s hidden, and the verb Î³ÏÎ¬Ï†Ï‰ grÃ¡fo write) is the study of message secrecy. ... A symmetric-key algorithm is an algorithm for cryptography that uses the same cryptographic key to encrypt and decrypt the message. ... Encryption Decryption In cryptography, a block cipher is a symmetric key cipher which operates on fixed-length groups of bits, termed blocks, with an unvarying transformation. ... The Data Encryption Standard (DES) is a cipher (a method for encrypting information) selected as an official Federal Information Processing Standard (FIPS) for the United States in 1976, and which has subsequently enjoyed widespread use internationally. ... In cryptography, the Advanced Encryption Standard (AES), also known as Rijndael, is a block cipher adopted as an encryption standard by the U.S. government. ... The key-schedule of DES (<<< denotes a left rotation) In cryptography, the so-called product ciphers are a certain kind of ciphers, where the (de-)ciphering of data is done in rounds. The general setup of each round is the same, except for some hard-coded parameters and a part... 1996 (MCMXCVI) was a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... In cryptography, a related-key attack is any form of cryptanalysis where the attacker can observe the operation of a cipher under several different keys whose values are initially unknown, but where some mathematical relationship connecting the keys is known to the attacker. ...

In 2004, Scott posted some comments on sci.crypt reflecting on the motivation behind NewDES's design and what he might have done differently to make the cipher more secure [1]. 2004 (MMIV) was a leap year starting on Thursday of the Gregorian calendar. ... There are several newsgroups relevant for discussions about cryptography and related issues. ...

## Contents

NewDES, unlike DES, has no bit-level permutations, making it easy to implement in software. All operations are performed on whole bytes. It is a product cipher, consisting of 17 rounds performed on a 64-bit data block and makes use of a 120-bit key. In each round, subkey material is XORed with the 1-byte sub-blocks of data, then fed through an S-box, the output of which is then XORed with another sub-block of data. In total, 8 XORs are performed in each round. The S-box is derived from the United States Declaration of Independence (to show that Scott had nothing up his sleeve). In cryptography, a product cipher is a popular type of block cipher that works by executing in sequence a number of simple transformations such as substitution, permutation, and modular arithmetic. ... A key is a piece of information that controls the operation of a cryptography algorithm. ... Exclusive disjunction (usual symbol xor) is a logical operator that results in true if one of the operands (not both) is true. ... In cryptography, a substitution box (or S-box) is a basic component of symmetric key algorithms. ... U.S. Declaration of Independence The Declaration of Independence is the document in which the Thirteen Colonies declared themselves independent of the Kingdom of Great Britain and explained their justifications for doing so. ... Nothing up my sleeve numbers are the the opposite extreme of Chaitin-Kolmogorov randomness in that they appear to be random by statistical tests but are created with minimum entropy. ...

Each set of two rounds uses seven 1-byte subkeys, which are derived by splitting 56 bits of the key into bytes. The key is then rotated 56 bits for use in the next two rounds.

## Cryptanalysis of NewDES

NewDES has the same complementation property that DES has: namely, that if

EK(P) = C,

then

$E_{overline{K}}(overline{P})=overline{C},$

where

$overline{x}$

is the bitwise complement of x. This means that the work factor for a brute force attack is reduced by a factor of 2. Eli Biham also noticed that changing a full byte in all the key and data bytes leads to another complementation property. This reduces the work factor by 28. The EFFs US\$250,000 DES cracking machine contained over 1,800 custom chips and could brute force a DES key in a matter of days â€” the photograph shows a DES Cracker circuit board fitted with several Deep Crack chips. ... Eli Biham is an Israeli cryptographer and cryptanalyst, currently a professor at the Technion Israeli Institute of Technology Computer Science department. ...

Biham's related-key attack can break NewDES with 233 chosen-key chosen plaintexts, meaning that NewDES is not as secure as DES.

John Kelsey, Bruce Schneier, and David Wagner used related-key cryptanalysis to develop another attack on NewDES; it requires 232 known plaintexts and one related key. John Kelsey is a cryptographer currently working at NIST. His research interests include cryptanalysis and design of symmetric cryptography primitives (block ciphers, stream ciphers, cryptographic hash functions, MACs), analysis and design of cryptographic protocols, cryptographic random number generation, electronic voting, side-channel attacks on cryptography implementations, and anonymizing communications systems. ... Bruce Schneier Bruce Schneier (born January 15, 1963) is an American cryptographer, computer security specialist, and writer. ... David Wagner David A. Wagner (1974) is an Assistant Professor of Computer Science at the University of California, Berkeley and a well-known researcher in cryptography. ...

Results from FactBites:

 BIGpedia - NewDES - Encyclopedia and Dictionary Online (408 words) Scott, the designer of NewDES, showed that NewDES exhibits the full avalanche effect after seven rounds: every ciphertext bit depends on every plaintext bit and key bit. This means that the work factor for a brute force attack is reduced by a factor of 2. NewDES therefore does not seem very secure: using Triple DES or AES instead would be more prudent.
 NewDES - Wikipedia, the free encyclopedia (425 words) NewDES, unlike DES, has no bit-level permutations, making it easy to implement in software. It is a product cipher, consisting of 17 rounds performed on a 64-bit data block and makes use of a 120-bit key. NewDES has the same complementation property that DES has: namely, that if
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