NewDES
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| General | |
|---|---|
| Designers | Robert Scott |
| First published | 1985 |
| Cipher detail | |
| Key sizes | 120 bits |
| Block sizes | 64 bits |
| Rounds | 17 |
| Best public cryptanalysis | |
| 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 quite a 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 2004, Scott posted some comments on sci.crypt reflecting on the motivation behind NewDES's design and what he might have done differently so as to make the cipher more secure.[1]
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 (used as a nothing-up-my-sleeve number).
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.
