
	Where results make sense

Topic: Linear feedback shift register

Related Topics

Primitive polynomial

Stream cipher

Shift register

NSA encryption systems

Rotor machine

Gray code

SIGSALY

SIGABA

Evariste Galois

Donut

EEPROM

ECHELON

National Security Agency

In the News (Thu 10 Dec 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Shift-Register Stream Ciphers
		2^7-1 is 127, and is the maximum period of a shift register built from a polynomial of degree 7.
		If only four shift registers are used, so that we XOR the output of one shift register with the output of a Geffe generator, then we still have the same weakness that the Geffe generator alone had.
		That is because the XOR of two LFSRs, by itself, is a linear construct, and thus is as vulnerable to attack as an LFSR of the length of the two combined.
	www.quadibloc.com /crypto/co040801.htm (2247 words)

	Linear feedback shift register
		A linear feedback shift register is a shift register whose input is the exclusive-or of some of its outputs.
		LFSR's can be implemented in hardware, and this makes them useful in applications that require very fast generation of a pseudo-random sequence, such as direct-sequence spread spectrum radio.
		LFSRs have long been used as a pseudo-random number generator for use in stream ciphers (especially in military cryptography), due to the ease of construction from simple electromechanical or electronic circuits, long periodss, and very uniformly distributed outputs.
	www.guajara.com /wiki/en/wikipedia/l/li/linear_feedback_shift_register.html (302 words)

	Parallel architecture for generating pseudo-random sequences (Technology/Intellectual Property Profile)
		The output sequence generated by such a shift register is typically taken from the feedback connection (the output of the logic tree), and is dependent upon the initial states of the N shift register cells, as well as the polynomial implemented in the logic tree.
		For an N-cell register, the contents of all N-cells are moved during each cycle, and taps are connected to certain shift register cells in the shift register to connect selected shift register cells to the combinatorial logic.
		Instead of shifting the bits past the taps, as in a conventional shift register implementation, in the present invention the taps are connected to the appropriate memory cells by a set of switches that selectively connect the taps to the proper memory cells in each cycle.
	www.uta.edu /ra/real/editprofile.php?pid=989&onlyview=1 (7688 words)

	Noise/Chaos/Random Numbers/Linear Feedback Shift Register
		Whether it shifts right or left does not really matter and is usually determined by the requirements of the circuit that the LFSR is driving or the method that it is being constructed by.
		If XORs are used to generate the feedback input to the shift register, then the state of all zeros is not allowed as the system would never leave the all zero state.
		LFSR are not truly random devices because after a certain number of cycles, the cycle out of the LFSR will repeat, hence they are termed "pseudo-random devices." The maximum number of cycles before the cycle repeats can be determined by the formula: (2^n)andndash;1.
	archive.chipcenter.com /circuitcellar/august99/c89r4.htm (3744 words)

	RSA Laboratories - 2.1.5.1 What is a Linear Feedback Shift Register?
		The behavior of the register is regulated by a counter (in hardware this counter is often referred to as a ``clock'').
		A shift register cascade is a set of LFSRs connected together in such a way that the behavior of one particular LFSR depends on the behavior of the previous LFSRs in the cascade.
		A variant of the shrinking generator is the self-shrinking generator [MS95b], where instead of using one output from one LFSR to "shrink" the output of another (as in the shrinking generator), the output of a single LFSR is used to extract bits from the same output.
	www.rsa.com /rsalabs/node.asp?id=2175 (484 words)

	Method and apparatus for replacing lost PSTN data in a packet network - Patent # 6208618 - PatentGenius
		In one preferred embodiment, a linear feedback shift register (LFSR) is used in conjunction with a feedback network corresponding to a polynomial generating function.
		At the receiver, a binary shift register produces a binary sequence that ismodulated with the noise metric to produce noise at the amplitude of the original background noise.
		Because the LFSR 100 output will be used to fill cells of missing data which may represent telephone conversation samples, the length 2.sup.n -1 is preferably long enough to prevent the sequence from repeating at a rate that creates an audible frequencycomponent in the telephone conversation.
	www.patentgenius.com /patent/6208618.html (5850 words)

	Linear Feedback Shift Registers
		A shift register is a device whose identifying function is to shift its contents into adjacent positions within the register or, in the case of the position on the end, out of the register.
		Clocking) One of the inputs to a shift register is the clock; a shift occurs in the register when this clock input changes state from one to zero (or from zero to one, depending on the implementation).
		By definition, the selected bit values are collected before the register is clocked and the result of the feedback function is inserted into the shift register during the shift, filling the position that is emptied as a result of the shift.
	homepage.mac.com /afj/lfsr.html (1687 words)

	Linear feedback shift register Information - linear feedback shift register for security
		A linear feedback shift register (sometimes called PN Sequences register) is a shift register whose input is the exclusive-or (xor) of some of its outputs.
		Linear Feedback Shift Register (LFSR) A shift register where the input bit is driven by a linear function of the overall shift register value.
		LFSR's linear feedback shift register algorithm can be implemented in hardware, and this makes them useful in applications that require very fast generation of a pseudo-random sequence, such as direct-sequence spread spectrum radio.
	www.inanot.com /Ina-Electronics_Topics_L_-_Ma-/Linear_feedback_shift_register.html (653 words)

	Q89: What is a Linear Feedback Shift Register?
		A Linear Feedback Shift Register (LFSR) is a mechanism for generating a sequence of binary bits.
		The register (see Figure 7) consists of a series of cells that are set by an initialization vector that is, most often, the secret key.
		The behavior of the register is regulated by a clock and at each clocking instant, the contents of the cells of the register are shifted right by one position, and the exclusive-or of a subset of the cell contents is placed in the leftmost cell.
	www.x5.net /faqs/crypto/q89.html (174 words)

	Tutorial: Linear Feedback Shift Registers (LFSRs) - Part 1
		The equivalent to the Ouroboros in the world of electronics would be the Linear Feedback Shift Register (LFSR), in which the output from a standard shift register is cunningly manipulated and fed back into its input in such a way as to cause the function to endlessly cycle through a sequence of patterns.
		All of the register elements share a common clock input, which is omitted from the symbol for reasons of clarity.
		The data input to the LFSR is generated by XOR-ing or XNOR-ing the tap bits; the remaining bits function as a standard shift register.
	www.embedded.com /shared/printableArticle.jhtml?articleID=196701707 (929 words)

	[No title]
		The shift register 69 is associated with feedback 70 in the same fashion as the LFSRs 53, 54, with the exception that the shift register 69 is loaded with new numbers before each cycle of shifting feedback iterations.
		Then a bitwise linear feedback shift register iteration subroutine 182 is performed in which each bit is shifted to the next higher order position, with or without inversion, dependent upon the secret mask and/or whether the low order bit position has a 1, as described hereinbefore.
		Then, a bitwise reverse LFSR iteration subroutine 235 is performed which looks at the low order bit to determine whether the bits corresponding to the mask should be flipped before they are shifted to the next lower order position in the shift register to reconstitute the original word prior to encryption.
	www.ece.cmu.edu /~koopman/patents/5377270/5377270.html (11792 words)

	RSA Laboratories - 2.1.5.1 What is a Linear Feedback Shift Register?
		The behavior of the register is regulated by a counter (in hardware this counter is often referred to as a ``clock'').
		A shift register cascade is a set of LFSRs connected together in such a way that the behavior of one particular LFSR depends on the behavior of the previous LFSRs in the cascade.
		A variant of the shrinking generator is the self-shrinking generator [MS95b], where instead of using one output from one LFSR to "shrink" the output of another (as in the shrinking generator), the output of a single LFSR is used to extract bits from the same output.
	www.rsasecurity.com /rsalabs/node.asp?id=2175 (484 words)

	Burst mode error detection and definition - Patent 4979173
		Register 72.sub.H functions alternately as a shift register or as a counter and is an important feature of the invention.
		Register 71.sub.H is an array of eight DFR cells, all driven by the signal write71, which signal functions similarly to the command write72 used in register 72.sub.H. Similarly, signal read71 and the DFR drivers DFRD in FIGS.
		Register 71.sub.H provides output signals indicating: (1) that the system is currently in the correction mode, and if so whether register 72.sub.H currently operates as a counter; (2) whether LFSR feedback is currently disabled (correction mode); and (3) which division polynomial P or P.sub.r, if either, should be currently used in the LFSR.
	www.freepatentsonline.com /4979173.html (9714 words)

	LFSRs
		Shift it to the right, and if the bit that falls off the end is 1 then XOR the register with a mask value, otherwise leave it alone.
		LFSRs that are maximal period cycle through 2^n-1 values before repeating, where n is the width of the register.
		To obtain a maximal period LFSR, the choice of the bits used for the XOR mask is critical.
	www.cryogenius.com /software/lfsr (484 words)

	LFSR Reference -- M-Sequence, Linear Feedback Shift Register, Feedback Taps for Maximal Length Sequences
		A linear feedback shift register (LFSR) is the heart of any digital system that relies on pseudorandom bit sequences (PRBS), with applications ranging from cryptography and bit-error-rate measurements, to wireless communication systems employing spread spectrum or CDMA techniques.
		The Fibonacci implementation consists of a simple shift register in which a binary-weighted modulo-2 sum of the taps is fed back to the input.
		When the feedback taps of an LFSR are non-maximal, the length of the generated sequence depends upon the initial state of the LFSR.
	www.ncu.edu.tw /~ncume_ee/digilogi/prbs.htm (2305 words)

	Linear Feedback Shift Registers
		Feedback Shift Registers are a commonly used method of producing pseudo-random sequences.
		Thus, linear feedback shift registers should not be used in cryptographic work (despite this, LFSR's are still the most commonly used technique).
		Def: The linear equivalence of a periodic sequence S(x) is the length n of the smallest LFSR that can generate S(x).
	www-math.cudenver.edu /~wcherowi/courses/m5410/m5410fsr.html (1615 words)

	Linear Feedback Shift Register
		feedback logic in which the initial value of the shift register, shift register taps, and feedback logic determines the output sequence.
		This scheme allows the user to load the shift register with an initialization sequence.
		is asserted, the megafunction configures itself to a normal shift register size of 32.
	www.altera.com /products/ip/dsp/signal_generation/m-nov-linear.html (249 words)

	EDACafe: ASICs .. the Book
		We assume the register is initialized to the all-ones state, but any initial state will work and produce the same PRBS, as long as the initial state is not all zeros (in which case the LFSR will stay stuck at all zeros).
		Figure 14.24 shows the LFSR of Figure 14.23 with an additional XOR gate used in the first stage of the shift register.
		The operation of LFSRs is related to the mathematics of polynomials and Galois-field theory.
	www.edacafe.com /books/ASIC/Book/CH14/CH14.7.php (2968 words)

	Linear Feedback Shift Register Sequence Generator for Specified Sequences
		The sequence source generator is a r-stage linear feedback shift register, as shown in the dotted line portion.
		The linear feedback shift register is characterized by a primitive polynomial.
		The property of a primitive polynomial is that the corresponding shift register generates all 2/r/-1 patterns of r digits (except the all-zero pattern).
	www.priorartdatabase.com /IPCOM/000078451 (328 words)

	United States Patent: 4,195,293
		Presetting the shift register to the same non-zero state causes it to generate the same pseudorandom sequence.
		By thus presetting the shift register during each field of a raster scan display at the same position of the raster, a stationary random pattern will be generated.
		Therefore by presetting the LFSR to the same non-zero state during each field at the same position of the raster, a stationary random pattern is generated on the display screen.
	www.jmargolin.com /patents/4195293.htm (2947 words)

	Linear Feedback Shift Registers in Mathematica
		With this package, you can generate bit sequeneces from LFSRs, and from bit sequences determine the minimal generating LFSR along with the linear complexity profile using the Berlekamp-Massey Algorithm.
		Linear Feedback Shift Registers (LFSR) are primarly used in cryptography and random number testing.
		Feedback welcome (pun intended) on which implementation is better.
	modp.com /release/mma_lfsr (333 words)

	CDG : Technology : Welcome to the World of CDMA
		The maximal-length binary sequences produced by linear feedback shift registers are widely used for direct sequence spectrum spreading.
		The so-called Fibonacci implementation consists of a simple shift register in which a binary weighted modulo 2 sum of the taps is fed back to the input.
		The linearity of the m-sequence generators and their properties as a representation of a finite field make it rather simple to offset a state by some prescribed number of states, or to create a transformation matrix that will produce a delayed version of the sequence from an undelayed state register.
	www.cdg.org /technology/cdma_technology/a_ross/LFSR.asp (1044 words)

	Kryptographie FAQ: Frage 89: What is a Linear Feedback Shift Register?
		The register (see Figure 7) consists of a series of cells that are set by an initialization vector that is, most often, the secret key.
		The behavior of the register is regulated by a clock and at each clocking instant, the contents of the cells of the register are shifted right by one position, and the exclusive-or of a subset of the cell contents is placed in the leftmost cell.
		However, the sequences generated by single LFSRs are not secure because a powerful mathematical framework has been developed over the years which allows for their straightforward analysis.
	www.iks-jena.de /mitarb/lutz/security/cryptfaq/q89.html (184 words)

	Two Dimensional Complementary Clock Linear Feedback Shift Register
		The location of feedback lines and input inverters and selecting clocks for flip-flops in the 2-D CCLFSR can also be designed by modifying the parameters, lead to 20% reduction in hardware overhead.
		One of the new structures is using two dimensional Linear Feedback Shift Register(2-D LFSR) or configurable 2-D LFSR [1,2] as the pattern generator for generating deterministic patterns and then pseudorandom patterns with low hardware overhead.
		In this paper a kind of 2-D LFSR called 2-D Complementary Clock LFSR (2-D CCLFSR) is introduced that uses a two-phase clock and adds additional choices for constructing a 2-D LFSR to generate the required deterministic patterns and gives additional options to the optimization software resulting in a less hardware overhead than before.
	www.ee.ryerson.ca /opr/research_projects/synthesis_2d_cclfsr.html (456 words)

Try your search on: Qwika (all wikis)