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Topic: Skipjack (cipher)

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Blowfish (cipher)

Twofish

Feistel cipher

Block cipher

GOST

Data Encryption Standard

Key size

Triple DES

Type 1 product

Type 1 encryption

RC4 (cipher)

Advanced Encryption Standard

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	Skipjack (cipher) Information
		Skipjack was proposed as the encryption algorithm in a US government-sponsored scheme of key escrow, and the cipher was provided for use in the Clipper chip, implemented in tamperproof hardware.
		[Skipjack] is representative of a family of encryption algorithms developed in 1980 as part of the NSA suite of "Type I" algorithms...
		SKIPJACK's more immediate heritage dates to around 1980, and its initial design to 1987...The specific structures included in SKIPJACK have a long evaluation history, and the cryptographic properties of those structures had many prior years of intense study before the formal process began in 1987.
	www.bookrags.com /Skipjack_encryption_algorithm (424 words)

	Glossary for Internet Cryptography
		Block cipher mode that feeds previously encrypted ciphertext through the block cipher to generate the key that encrypts the next block of ciphertext.
		A cipher that uses a pair of keys, a public key and private key, for encryption and decryption.
		Cipher developed for encrypting teletype traffic by computing the exclusive or of the data bits and the key bits.
	www.smat.us /crypto/inet-crypto/glossary.html (4125 words)

	Strong Encryption Package, Skipjack
		Skipjack is a recent algorithm that was developed in 1987 and put into service in 1993.
		Skipjack is a representative of a family of encryption algorithms developed in 1980 as part of the NSA suite of "Type I" algorithms, which are suitable for protecting all levels of classified data.
		In 1993 an Interim Report was released that gave a thorough analysis of Skipjack and discussed issues relating to Skipjack's integration in the Clipper and Fortezza hardware.
	www.tropsoft.com /strongenc/skipjack.htm (1369 words)

	RFC 2876 - Use of the KEA and SKIPJACK Algorithms in CMS
		SKIPJACK CEK Wrap Process The SKIPJACK CEK is uniquely wrapped for each recipient of the EnvelopedData using a pairwise KEK generated using the KEA material of the originator and the recipient along with the originator's User Keying Material (UKM) (i.e.
		SKIPJACK CEK Wrap Process Using A Shared Originator UKM Value This section describes how a shared originator UKM value is used as an input to KEA to generate each pairwise KEK used to wrap the SKIPJACK CEK for each recipient.
		SKIPJACK CEK Wrap Process Using Unique Originator UKM Values This section describes how a unique originator UKM value is generated for each recipient to be used as an input to KEA to generate that recipient's pairwise KEK.
	www.packetizer.com /rfc/rfc2876 (3171 words)

	Cryptanalysis of SkipJack-4XOR
		SkipJack is the secret key encryption algorithm used by the US government in the Clipper chip and Fortezza PC card.
		This phenomena is the combination of the XOR structure of the last Rule A round and the first Rule B round, that actually exchanges the two leftmost words, together with the change of the direction of the XOR mixing arrows from right-to-left to left-to-right.
		In this note we consider variants of SkipJack which are identical to the original version except for the removal of a few XOR operations.
	www.cs.technion.ac.il /~biham/Reports/SkipJack/note2.html (2079 words)

	Initial Observations on the SkipJack Encryption Algorithm
		The published description of SkipJack characterizes the rounds as either Rule A or Rule B. Each round is described in the form of a linear feedback shift register with additional non linear keyed G permutation.
		SkipJack applies eight rounds of Rule A, followed by eight rounds of Rule B, followed by another eight rounds of Rule A, followed by another eight rounds of Rule B. The Software implementation becomes simpler and more efficient if we unroll the rounds, and keep the four elements in the shift register stationary.
		We found for this cipher a 16-round characteristic with considerably higher probability of about 2^{-52.1} rather than about 2^{-72.9} in the case of SkipJack (this characteristic's plaintext difference is (0,0, a,0, a,b, 0,0)).
	www.cs.technion.ac.il /~biham/Reports/SkipJack/note1.html (1543 words)

	Using TLS, SLL, PCT in secure communications (Site not responding. Last check: 2007-10-20)
		For stream ciphers that do not use a synchronization vector (such as RC4), the stream cipher state from the end of one record is simply used on the subsequent packet.
		For block ciphers (such as RC2 or DES) padding is added to force the length of the plaintext to be a multiple of the block cipher's block length.
		SSL's client authentication is independent of the cipher strength used in the session and is also independent of whether the authentication is being performed for a reconnection of an old session or for a new one.
	cactus.eas.asu.edu /partha/Teaching/Archive/Crypto.1999S/slavinsky.html (2534 words)

	Quadibloc III
		The cipher SKIPJACK may be protected by patents, preventing this cipher from being generally available for use in its present form.
		The concept of a cipher called Mishmash is noted in the conclusions section of this chapter, to which reference may be required.
		The four Skipjack rounds are type A in the first two Mishmash rounds in the cipher, and type B in the last two.
	www.quadibloc.com /crypto/co040706.htm (5881 words)

	More Realistic Examples
		Also, the SKIPJACK block cipher design was described in the document revealing its design as a kind of shift register, suggesting how a shift register could be used for a simplified form of block encipherment.
		It may be noted that this arrangement, although it is greatly simplified, is essentially a scaled down version of operating a block cipher in Cipher Feed-Back mode, with the addition that the "block cipher" output is further condensed by a nonlinear function of several of its bits.
		As the second one is based on various public comments concerning the electronic cipher machines of the U.S. during that period, although it is scaled down, it may illustrate a principle that had actually been used, or, of course, one that we are intended to think was used.
	www.quadibloc.com /crypto/co4813.htm (1763 words)

	Eric's Crypto Software
		SKIPJACK is a relatively recent algorithm, and has not yet been subject to nearly as much public scrutiny.
		SKIPJACK uses 32 rounds, twice as many as DES, but because it is constructed of simpler operations it actually runs about twice as fast, and does not require any key setup time.
		The SKIPJACK source code is available under the terms of the Free Software Foundation's General Public License, Version 2.
	www.brouhaha.com /~eric/crypto (843 words)

	Crypto-Gram: July 15, 1998
		Skipjack is a 64-bit symmetric block cipher with an 80-bit key.
		Skipjack is a good target; it is an algorithm designed using secret methodologies by an organization we respect.
		Skipjack is an unbalanced Feistel network (specifically, an incomplete construction), but it is obviously a product of military cryptography.
	www.schneier.com /crypto-gram-9807.html (2428 words)

	Strong Encryption Package, Product Information
		Rijndael is a block cipher designed by Joan Daemen and Vincent Rijmen as a candidate algorithm for the Advanced Encryption Standard (AES).
		MARS is a block cipher designed by IBM as a candidate algorithm for the Advanced Encryption Standard (AES).
		Skipjack is a formerly secret NSA encryption algorithm that was declassified in 1998.
	www.tropsoft.com /strongenc/prodinfo.htm (713 words)

	ISC CDK 7: EES Class Reference
		EES is an 8-byte block cipher with a key size of 80 bits.
		Sample code illustrating the use of this class appears in the Cookbook section Using the Symmetric Ciphers.
		EES is specified in FIPS 185 and SKIPJACK and KEA Algorithm Specifications.
	www.infoseccorp.com /products/cdk/html/classcdk_1_1_e_e_s.html (304 words)

	Cryptosystems and Keys (Site not responding. Last check: 2007-10-20)
		Any monoalphabetic substitution cipher can be broken by comparing the relative frequencies of occurrence of the letters in intercepted ciphertext samples with the corresponding statistics for letters in plaintext examples of related writings.
		Over two decades of unsuccessful cryptanalysis have shown the DES cipher's cryptographic strength to be, in practical terms, equivalent to the size of its key.
		This mandates use of the now-declassified Skipjack cipher with an 80-bit key (16 million times the size of the 56-bit DES keyspace), and a Law Enforcement Access Field (LEAF) permitting key recovery without the user's cooperation.
	www.cerberussystems.com /INFOSEC/tutorial/keys.htm (2222 words)

	Introduction to SSL - MDC
		Clients and servers may support different cipher suites, or sets of ciphers, depending on factors such as the version of SSL they support, company policies regarding acceptable encryption strength, and government restrictions on export of SSL-enabled software.
		Decisions about which cipher suites a particular organization decides to enable depend on trade-offs among the sensitivity of the data involved, the speed of the cipher, and the applicability of export rules.
		However, since 40-bit ciphers can be broken relatively quickly, administrators whose user communities can use stronger ciphers without violating export restrictions should disable the 40-bit ciphers if they are concerned about access to data by eavesdroppers.
	developer.mozilla.org /en/docs/Introduction_to_SSL (4580 words)

	Skipjack (cipher) - Wikipedia, the free encyclopedia
		Eli Biham and Adi Shamir discovered an attack against 16 of the 32 rounds within one day of declassification, and (with Alex Biryukov) extended this to 31 of the 32 rounds within months using impossible differential cryptanalysis.
		In 2002, R. Chung-Wei Phan published a complementation slide attack against the full Skipjack cipher (all 32 rounds).
		It was found, however, that the attack is flawed; Biham, Shamir and Biryukov's attack continues to be the best cryptanalysis of Skipjack known to the public.
	en.wikipedia.org /wiki/Skipjack_(cipher) (528 words)

	RFC 2951 - TELNET Authentication Using KEA and SKIPJACK
		Mutual authentication is provided by verification of the certificates used to establish the SKIPJACK encryption key and successful use of the derived SKIPJACK session key.
		SKIPJACK Modes There are two distinct modes for encrypting TELNET streams; one provides integrity and the other does not.
		The cryptographic mode for SKIPJACK with stream integrity is Cipher Feedback on 32 bits of data (CFB-32) and the mode of SKIPJACK is Cipher Feedback on 8 bits of data (CFB-8).
	members.tripod.com /rfc_archive/rfc_2951.html (1785 words)

	Carlton O'Riley
		I propose to implement the Skipjack algorithm and Key Exchange Algorithms in C/C++ using some assembly code routines to optimize the encryption and decryption speeds.
		The Skipjack algorithm has four modes of operation, Output Feedback (OFB), Cipher Feedback (CFB), Codebook (CBE), and Cipher-Block Chaining (CBC), which are subsets of the FIPS-81 description of modes of operation for DES.
		To perform the performance comparisons between DES and this implementation of Skipjack the randomly generated files of varying sizes will be encrypted and decrypted.
	mason.gmu.edu /~kgaj/ECE590/spec/carlton.html (877 words)

	RFC 2876
		This document describes the conventions for using the Key Exchange Algorithm (KEA) and SKIPJACK encryption algorithm in conjunction with the Cryptographic Message Syntax [CMS] enveloped-data and encrypted- data content types.
		The SKIPJACK CEK is uniquely wrapped for each recipient of the EnvelopedData using a pairwise KEK generated using the KEA material of the originator and the recipient along with the originator's User Keying Material (UKM) (i.e.
		This section describes the recipient processing using KEA to generate the SKIPJACK KEK and the subsequent decryption of the SKIPJACK CEK.
	library.n0i.net /rfc/html/rfc2876.html (3067 words)

	Introduction to SSL (Site not responding. Last check: 2007-10-20)
		However, since 40-bit ciphers can be broken relatively quickly, administrators who are concerned about eavesdropping and whose user communities can legally use stronger ciphers should disable the 40-bit ciphers.
		Cipher suites are listed from strongest to weakest; for more information about the way encryption strength is measured, see Key Length and Encryption Strength.
		Because the RC4 and RC2 ciphers have 128-bit encryption, they are the second strongest next to Triple DES (Data Encryption Standard), with 168-bit encryption.
	docs.sun.com /source/816-6156-10/contents.htm (5090 words)

	Encryption algorithms
		The results of the previously chained block is used in the encryption of the next chained block.
		A sequence of values that are used with a cipher algorithm to encrypt a message.
		The choice of random (or cryptographically pseudorandom) keys, a secure key exchange mechanism, frequent key refreshments, and good secrecy protection of keys are all essential ingredients for the security of the integrity verification mechanism.
	www.networksorcery.com /enp/data/encryption.htm (692 words)

	Algorithms and Attacks
		Breaking a cipher doesn't necessarily mean finding a practical way for an eavesdropper to recover the plaintext from just the ciphertext.
		Breaking a cipher simply means finding a weakness in the cipher that can be exploited with a complexity less than brute-force.
		SKIPJACK and KEA specifications - Pages 1-17 [PDF, 819KB] from NIST.
	users.castel.nl /~groor01/algoritak.htm (277 words)

	Skipjack - Wikipedia, the free encyclopedia
		the Skipjack tuna, a fish of the Scombridae (tuna) family.
		the skipjack, a type of fishing boat used on the Chesapeake Bay, USA.
		Skipjack the block cipher designed by the NSA.
	en.wikipedia.org /wiki/Skipjack (150 words)

	[No title]
		A cypherpunk reposted the almost 5 year old Skipjack review which claimed that while the algorithm was strong, its release would "jeopardize law enforcement and national security objectives." I'd love for someone to comment on why it no longer does, but I suppose that would still be protected.
		Text of the current bills (S 2037 and HR 2281) along with their status and references to them in the Congressional Record may be found at http://thomas.loc.gov/ Also found their is the alternative (HR 3048).
		Reviewed by Robert Bruen, Cipher Book Review Editor ____________________________________________________________________ When SATAN was first released about four years ago, it caused quite a stir in the press and and in the field.
	www.ieee-security.org /Cipher/PastIssues/1998/issue9807/issue9807.txt (19168 words)

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