cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

, New Data Seal (NDS) is a

block cipher In cryptography, a block cipher is a deterministic algorithm operating on fixed-length groups of bits, called ''blocks''. Block ciphers are specified cryptographic primitive, elementary components in the design of many cryptographic protocols and ...

that was designed at IBM in 1975, based on the

Lucifer Lucifer is one of various figures in folklore associated with the planet Venus. The entity's name was subsequently absorbed into Christianity as a name for the devil. Modern scholarship generally translates the term in the relevant Bible passage ...

algorithm that became

DES Des is a masculine given name, mostly a short form (hypocorism) of Desmond. People named Des include: People * Des Buckingham, English football manager * Des Corcoran, (1928–2004), Australian politician * Des Dillon (disambiguation), sever ...

. The cipher uses a block size of 128 bits, and a very large

key size In cryptography, key size, key length, or key space refer to the number of bits in a key used by a cryptographic algorithm (such as a cipher). Key length defines the upper-bound on an algorithm's security (i.e. a logarithmic measure of the fastest ...

of 2048 bits. Like DES it has a 16-round

Feistel network In cryptography, a Feistel cipher (also known as Luby–Rackoff block cipher) is a symmetric structure used in the construction of block ciphers, named after the German-born physicist and cryptographer Horst Feistel, who did pioneering research whi ...

structure. The round function uses two fixed 4×4-bit

S-boxes In cryptography, an S-box (substitution-box) is a basic component of symmetric key algorithms which performs substitution. In block ciphers, they are typically used to obscure the relationship between the key and the ciphertext, thus ensuring Shan ...

, chosen to be non-

affine Affine may describe any of various topics concerned with connections or affinities. It may refer to: * Affine, a relative by marriage in law and anthropology * Affine cipher, a special case of the more general substitution cipher * Affine comb ...

. The

key Key or The Key may refer to: Common meanings * Key (cryptography), a piece of information that controls the operation of a cryptography algorithm * Key (lock), device used to control access to places or facilities restricted by a lock * Key (map ...

is also treated as an 8×8-bit lookup table, using the first bit of each of the 8 bytes of the half-block as input. The nth bit of the output of this table determines whether or not the two

nibble In computing, a nibble (occasionally nybble, nyble, or nybl to match the spelling of byte) is a four-bit aggregation, or half an octet. It is also known as half-byte or tetrade. In a networking or telecommunication context, the nibble is oft ...

s of the nth byte are swapped after S-box substitution. All rounds use the same table. Each round function ends with a fixed

permutation In mathematics, a permutation of a set is, loosely speaking, an arrangement of its members into a sequence or linear order, or if the set is already ordered, a rearrangement of its elements. The word "permutation" also refers to the act or proc ...

of all 64 bits, preventing the cipher from being broken down and analyzed as a system of simpler independent subciphers. In 1977,

Edna Grossman Edna Grossman (born Edna Kalka) is an American mathematician. She was born in Germany, grew up in Brooklyn, New York, and graduated with a B.S. in mathematics from Brooklyn College. She earned her M.S. in mathematics from New York University's Cour ...

and

Bryant Tuckerman Louis Bryant Tuckerman, III (November 28, 1915 – May 19, 2002) was an American mathematician, born in Lincoln, Nebraska. He was a member of the team that developed the Data Encryption Standard (DES). He studied topology at Princeton, where he i ...

cryptanalyzed NDS using the first known

slide attack The slide attack is a form of cryptanalysis designed to deal with the prevailing idea that even weak ciphers can become very strong by increasing the number of rounds, which can ward off a differential attack. The slide attack works in such a way ...

. This method uses no more than 4096 chosen plaintexts; in their best trial they recovered the key with only 556 chosen plaintexts.

References

* * Broken block ciphers Feistel ciphers {{crypto-stub