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NewDES
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NewDES

In cryptography, NewDES is a symmetric key block cipher. It was created in 19841985 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 vulnerability; this version is sometimes referred to as NewDES-96.

Table of contents
1 The algorithm
2 Cryptanalysis of NewDES
3 External links
4 References

The algorithm

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 a round function, the result of which is then XORed with another sub-block of data. In total, 8 XORs are performed in each round. The round function is derived from the United States Declaration of Independence.

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

Robert 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.

NewDES has the same complementation property that DES has: if

then

where

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'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. NewDES therefore does not seem very secure: using Triple DES or AES instead would be more prudent.

External links

References


Block ciphers
Algorithms: 3-Way | AES | Blowfish | Camellia | CAST-128 | CAST-256 | CMEA | DEAL | DES | DES-X | FEAL | G-DES | GOST | IDEA | Iraqi | KASUMI | KHAZAD | Khufu and Khafre; | LOKI89/91 | LOKI97 | Lucifer | MacGuffin | Madryga | MAGENTA | MARS | MISTY1 | MMB | NewDES | RC2 | RC5 | RC6 | Red Pike; | S-1 | SAFER | Serpent | SHARK | Skipjack | Square | TEA | Triple DES; | Twofish | XTEA
Design: Feistel network; | Key schedule; | Product cipher; | S-box | SPN   Attacks: Brute force; | Linear / Differential cryptanalysis | Mod n; | XSL   Standardisation: AES process; | CRYPTREC | NESSIE   Misc: Avalanche effect | Block size; | IV | Key size; | Modes of operation; | Piling-up lemma; | Weak key;