Data Encryption Standard
Data Encryption Standard
Looking For data encryption standard? Find Data Encryption Here Today.
DataEncryption.TechSerious.com
Data Encryption Standard
Looking for Data Encryption Standard? Find It Locally.
purelocal.com/data-encryption
Xceed Encryption Library Version 1.0
Add strong encryption to your Windows apps, quickly and easily. This ActiveX component offers the new industry standard (AES) Rijndael algorythm, Twofish and RSA public-key. Download it now.
www.xceedsoft.com
Make DES Encryption Easy
One single API for all languages. .Net, Java, VB, C++, C and more.
www.cryptotools.com/des
Data Encryption Standard at Amazon
Buy books at Amazon.com and save. Qualified orders over $25 ship free.
Amazon.com/books
Encryption
Looking for advanced encryption standard? Visit our exclusive guide.
www.encryptionz.info
Data Encryption Standard
Data encryption standard and More! from Top Brands at Low Prices.
www.pricerunner.com
Encryption
Search great sites about encryption algorithm here.
www.encryptionz.org
Des Encryption
Save on all your networking needs from Exava. Shop Smart and Save.
www.exava.com
Data Encryption Software
Buy Affordable Computers at SHOP.COM. Toll-free shopping assistance.
www.SHOP.com
Warning: mkdir() [function.mkdir]: Permission denied in /home/webs/affiliatelib2/CacheManager.php on line 12
Warning: mkdir() [function.mkdir]: No such file or directory in /home/webs/affiliatelib2/CacheManager.php on line 12
Warning: fopen(/home/templatecore2cache//*cluesnet.com/d1/d12879108314e5c489f01c1766cd4289d61af538.tc2cache) [function.fopen]: failed to open stream: No such file or directory in /home/webs/affiliatelib2/CacheManager.php on line 130
Warning: fwrite(): supplied argument is not a valid stream resource in /home/webs/affiliatelib2/CacheManager.php on line 131
Warning: fclose(): supplied argument is not a valid stream resource in /home/webs/affiliatelib2/CacheManager.php on line 132
{{Infobox block cipher| name = Data Encryption Standard| image = | caption = The Feistel function (F function) of DES| designers = IBM| derived to = [Triple DES, G-DES, DES-X, LOKI89, ICE (cipher)| key size = 56 bits| block size = 64 bits| structure = Feistel network is possible (see [EFF DES cracker). As of 2004, the best analytical attack is linear cryptanalysis, which requires 243 known plaintexts and has a time complexity of 239–43 (Junod, 2001); under a chosen-plaintext assumption, the data complexity can be reduced by a factor of four (Knudsen and Mathiassen, 2000).-->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. The algorithm was initially controversial, with classified information design elements, a relatively short key length, and suspicions about a National Security Agency (NSA) Backdoor (computing). DES consequently came under intense academic scrutiny, and motivated the modern understanding of block ciphers and their cryptanalysis.
DES is now considered to be insecure for many applications. This is chiefly due to the 56-bit key size being too small; DES keys have been broken in less than 24 hours. There are also some analytical results which demonstrate theoretical weaknesses in the cipher, although they are infeasible to mount in practice. The algorithm is believed to be practically secure in the form of Triple DES, although there are theoretical attacks. In recent years, the cipher has been superseded by the Advanced Encryption Standard (AES).
In some documentation, a distinction is made between DES as a standard, and the algorithm, which is referred to as the DEA (the Data Encryption Algorithm). When spoken, "DES" is either spelled out (dee-ee-ess) or pronounced as a single syllable (dez or dess).
History of DES The origins of DES go back to the early 1970s. In 1972, after concluding a study on the US government's computer security needs, the US standards body NBS (National Bureau of Standards) — now named NIST (National Institute of Standards and Technology) — identified a need for a government-wide standard for encrypting unclassified, sensitive information. Accordingly, on 15 May 1973, after consulting with the NSA, NBS solicited proposals for a cipher that would meet rigorous design criteria. None of the submissions, however, turned out to be suitable. A second request was issued on 27 August 1974. This time, International Business Machines submitted a candidate which was deemed acceptable, a cipher developed during the period 1973–1974 based on an earlier algorithm, Horst Feistel's Lucifer (cipher) cipher. The team at IBM involved in cipher design and analysis included Feistel, Walter Tuchman, Don Coppersmith, Alan Konheim, Carl Meyer, Mike Matyas, Roy Adler, Edna Grossman, Bill Notz, Lynn Smith, and Bryant Tuckerman.
NSA's involvement in the design On March 17, 1975, the proposed DES was published in the Federal Register. Public comments were requested, and in the following year two open workshops were held to discuss the proposed standard. There was some criticism from various parties, including from public-key cryptography pioneers Martin Hellman and Whitfield Diffie, citing a shortened key length and the mysterious "Substitution boxes" as evidence of improper interference from the NSA. The suspicion was that the algorithm had been covertly weakened by the intelligence agency so that they — but no-one else — could easily read encrypted messages. Alan Konheim (one of the designers of DES) commented, "We sent the S-boxes off to Washington. They came back and were all different." The United States Senate Select Committee on Intelligence reviewed the NSA's actions to determine whether there had been any improper involvement. In the unclassified summary of their findings, published in 1978, the Committee wrote: "In the development of DES, NSA convinced IBM that a reduced key size was sufficient; indirectly assisted in the development of the S-box structures; and certified that the final DES algorithm was, to the best of their knowledge, free from any statistical or mathematical weakness." However, it also found that "NSA did not tamper with the design of the algorithm in any way. IBM invented and designed the algorithm, made all pertinent decisions regarding it, and concurred that the agreed upon key size was more than adequate for all commercial applications for which the DES was intended." Another member of the DES team, Walter Tuchman, is quoted as saying, "We developed the DES algorithm entirely within IBM using IBMers. The NSA did not dictate a single wire!"
Some of the suspicions about hidden weaknesses in the S-boxes were allayed in 1990, with the independent discovery and open publication by Eli Biham and Adi Shamir of differential cryptanalysis, a general method for breaking block ciphers. The S-boxes of DES were much more resistant to the attack than if they had been chosen at random, strongly suggesting that IBM knew about the technique back in the 1970s. This was indeed the case — in 1994, Don Coppersmith published the original design criteria for the S-boxes. According to Steven Levy, IBM Watson researchers discovered differential cryptanalytic attacks in 1974 and were asked by the NSA to keep the technique secret.Levy, Crypto, p. 55 Coppersmith explains IBM's secrecy decision by saying, "that was because cryptanalysis can be a very powerful tool, used against many schemes, and there was concern that such information in the public domain could adversely affect national security." Levy quotes Walter Tuchman: "hey asked us to stamp all our documents confidential... We actually put a number on each one and locked them up in safes, because they were considered U.S. government classified. They said do it. So I did it".Levy, p. 55 Shamir himself commented, "I would say that, contrary to what some people believe, there is no evidence of tampering with the DES so that the basic design was weakened."
The other criticism — that the key length was too short — was supported by the fact that the reason given by the NSA for reducing the key length from 64 bits to 56 was that the other 8 bits could serve as parity bits, which seemed somewhat specious. It was widely believed that NSA's decision was motivated by the possibility that they would be able to brute force attack a 56 bit key several years before the rest of the world would.
The algorithm as a standard Despite the criticisms, DES was approved as a federal standard in November 1976, and published on 15 January 1977 as FIPS PUB 46, authorized for use on all unclassified data. It was subsequently reaffirmed as the standard in 1983, 1988 (revised as FIPS-46-1), 1993 (FIPS-46-2), and again in 1998 (FIPS-46-3), the latter prescribing "Triple DES" (see below). On 26 May 2002, DES was finally superseded by Advanced Encryption Standard, the Advanced Encryption Standard, following a public competition (see AES process). Even as of 2004, however, DES remains in widespread use. On 19 May 2005, FIPS 46-3 was officially withdrawn, but NIST has approved Triple DES through the year 2030 for sensitive government information.
Another theoretical attack, linear cryptanalysis, was published in 1994, but it was a brute force attack in 1998 that demonstrated that DES could be attacked very practically, and highlighted the need for a replacement algorithm. These and other methods of cryptanalysis are discussed in more detail later in the article.
The introduction of DES is considered to have been a catalyst for the academic study of cryptography, particularly of methods to crack block ciphers. According to a NIST retrospective about DES, The DES can be said to have "jump started" the nonmilitary study and development of encryption algorithms. In the 1970s there were very few cryptographers, except for those in military or intelligence organizations, and little academic study of cryptography. There are now many active academic cryptologists, mathematics departments with strong programs in cryptography, and commercial information security companies and consultants. A generation of cryptanalysts has cut its teeth analyzing (that is trying to "crack") the DES algorithm. In the words of cryptographer Bruce Schneier ,Bruce Schneier, Applied Cryptography, Protocols, Algorithms, and Source Code in C, Second edition, John Wiley and Sons, New York (1996) p. 267 "DES did more to galvanize the field of cryptanalysis than anything else. Now there was an algorithm to study." An astonishing share of the open literature in cryptography in the 1970s and 1980s dealt with the DES, and the DES is the standard against which every symmetric key algorithm since has been compared.William E. Burr, "Data Encryption Standard", in NIST's anthology "A Century of Excellence in Measurements, Standards, and Technology: A Chronicle of Selected NBS/NIST Publications, 1901–2000. HTML PDF
Chronology {| class="wikitable" style="font-size:85%"! Date! Year! Event|-| 15 May| 1974| NBS publishes a second request for encryption algorithms|-| [17 March| 1977| DES is published as a FIPS standard FIPS PUB 46|-|| 1983| DES is reaffirmed for the first time|-|| 1986| [Videocipher II, a TV satellite scrambling system based upon DES begins use by HBO]| 1988| DES is reaffirmed for the second time as FIPS 46-1, superseding FIPS PUB 46|-| July| 1990| Biham and Shamir rediscover differential cryptanalysis, and apply it to a 15-round DES-like cryptosystem.]. However, it requires an unrealistic 247 chosen plaintexts.]| 1993| DES is reaffirmed for the third time as FIPS 46-2|-|| 1994| The first experimental cryptanalysis of DES is performed using linear cryptanalysis (Matsui, 1994).] breaks a message encrypted with DES for the first time in public.|-| July| 1998| The Electronic Frontier Foundation's EFF DES cracker (Deep Crack) breaks a DES key in 56 hours.|-| January| 1999| Together, Deep Crack and distributed.net break a DES key in 22 hours and 15 minutes.]| 1999| DES is reaffirmed for the fourth time as FIPS 46-3, which specifies the preferred use of Triple DES, with single DES permitted only in legacy systems.]| 2001| The Advanced Encryption Standard is published in FIPS 197]| 2002| The AES standard becomes effective|-| [26 July| 2005| NIST withdraws FIPS 46-3|-| [15 March of the University of Bochum and Kiel, Germany, breaks DES in 6.4 days at $10,000 hardware cost|}
Replacement algorithms Concerns about security and the relatively slow operation of DES in software motivated researchers to propose a variety of alternative block cipher designs, which started to appear in the late 1980s and early 1990s: for example RC5, Blowfish (cipher), International Data Encryption Algorithm, NewDES, SAFER, CAST5 and FEAL. Most of these designs kept the 64-bit block size of DES, and could act as a "drop-in" replacement, although they typically used a 64-bit or 128-bit key. In the USSR the GOST 28147-89 algorithm was introduced, with a 64-bit block size and a 256-bit key, which was also used in Russia later.
DES itself can be adapted and reused in a more secure scheme. Many former DES users now use Triple DES (TDES) which was described and analysed by one of DES's patentees (see Federal Information Processing Standard Pub 46-3); it involves applying DES three times with two (2TDES) or three (3TDES) different keys. TDES is regarded as adequately secure, although it is quite slow. A less computationally expensive alternative is DES-X, which increases the key size by XORing extra key material before and after DES. GDES was a DES variant proposed as a way to speed up encryption, but it was shown to be susceptible to differential cryptanalysis.
In 2001, after an international competition, NIST selected a new cipher, the Advanced Encryption Standard (AES), as a replacement. The algorithm which was selected as the AES was submitted by its designers under the name Rijndael. Other finalists in the NIST AES competition included RC6, Serpent (cipher), MARS, and Twofish.
Description For brevity, the following description omits the exact transformations and permutations which specify the algorithm; for reference, the details can be found in DES supplementary material. DES is the archetypal block cipher — an algorithm that takes a fixed-length string of plaintext bits and transforms it through a series of complicated operations into another ciphertext bitstring of the same length. In the case of DES, the block size (cryptography) is 64 bits. DES also uses a key (cryptography) to customize the transformation, so that decryption can only be performed by those who know the particular key used to encrypt. The key ostensibly consists of 64 bits; however, only 56 of these are actually used by the algorithm. Eight bits are used solely for checking parity, and are thereafter discarded. Hence the effective key length is 56 bits, and it is usually quoted as such.
Like other block ciphers, DES by itself is not a secure means of encryption but must instead be used in a block cipher mode of operation. FIPS-81 specifies several modes for use with DES . Further comments on the usage of DES are contained in FIPS-74 .
Overall structure The algorithm's overall structure is shown in Figure 1: there are 16 identical stages of processing, termed rounds. There is also an initial and final permutation, termed IP and FP, which are inverse (function)s (IP "undoes" the action of FP, and vice versa). IP and FP have almost no cryptographic significance, but were apparently included in order to facilitate loading blocks in and out of mid-1970s hardware, as well as to make DES run slower in software.
Before the main rounds, the block is divided into two 32-bit halves and processed alternately; this criss-crossing is known as the Feistel scheme. The Feistel structure ensures that decryption and encryption are very similar processes — the only difference is that the subkeys are applied in the reverse order when decrypting. The rest of the algorithm is identical. This greatly simplifies implementation, particularly in hardware, as there is no need for separate encryption and decryption algorithms.
The red ⊕ symbol denotes the XOR (XOR) operation. The F-function scrambles half a block together with some of the key. The output from the F-function is then combined with the other half of the block, and the halves are swapped before the next round. After the final round, the halves are not swapped; this is a feature of the Feistel structure which makes encryption and decryption similar processes.
The Feistel (F) function The F-function, depicted in Figure 2, operates on half a block (32 bits) at a time and consists of four stages:
The alternation of substitution from the S-boxes, and permutation of bits from the P-box and E-expansion provides so-called "confusion and diffusion" respectively, a concept identified by Claude Shannon in the 1940s as a necessary condition for a secure yet practical cipher.
Key schedule Figure 3 illustrates the key schedule for encryption — the algorithm which generates the subkeys. Initially, 56 bits of the key are selected from the initial 64 by Permuted Choice 1 (PC-1) — the remaining eight bits are either discarded or used as parity check bits. The 56 bits are then divided into two 28-bit halves; each half is thereafter treated separately. In successive rounds, both halves are rotated left by one or two bits (specified for each round), and then 48 subkey bits are selected by Permuted Choice 2 (PC-2) — 24 bits from the left half, and 24 from the right. The rotations (denoted by "
Data Encryption Standard from FOLDOC
Data Encryption Standard (DES) The NBS 's popular, standard encryption algorithm. It is a product cipher that operates on 64-bit blocks of data, using a 56-bit key.
Data Encryption Standard
The Free Online Dictionary of Computing (http://foldoc.doc.ic.ac.uk/) is edited by Denis Howe < dbh@doc.ic.ac.uk >. Previous: Data Encryption Key Next: data flow
Data Encryption Standard - Wikipedia, the free encyclopedia
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 ...
FIPS 46-2 - (DES), Data Encryption Standard
FIPS PUB 46-2 Supersedes FIPS PUB 46-1 1988 January 22. Federal Information Processing Standards Publication 46-2 1993 December 30 Announcing the Standard for
Dictionary of Computers - Data Encryption Standard
Skip to page content | Tiscali Quicklinks. Please visit our Accessibility Page for a list of the Access Keys you can use to find your way around the site, skip directly to the main ...
Amazon.co.uk: Brute Force: Cracking the Data Encryption Standard: Matt ...
Amazon.co.uk: Brute Force: Cracking the Data Encryption Standard: Matt Curtin: Books ... Hardcover: 291 pages; Publisher: Springer-Verlag New York Inc. (17 Mar 2005) Language ...
Data Encryption Algorithm from FOLDOC
Data Encryption Algorithm (DEA) An ANSI standard defined in ANSI X3.92-1981. It is identical to the Data Encryption Standard (DES). (1994-12-06) Try this search on Wikipedia ...
Data encryption standard for credit reporting | OUT-LAW.COM
The three major US credit reporting agencies, Equifax, Experian and TransUnion, yesterday announced that they would protect sensitive consumer data by using a single encryption ...
Triple DES - Wikipedia, the free encyclopedia
In cryptography, Triple DES is a block cipher formed from the Data Encryption Standard (DES) cipher by using it three times.
Data Encryption Standard
To view the documents indexed under a topic, click on the term. For more specific and related terms, click on Related Topics.