Dirac equation: Difference between revisions
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{{more footnotes|date=September 2013}} | |||
{{primary sources|date=September 2013}} | |||
'''Blum Blum Shub''' ('''B.B.S.''') is a [[pseudorandom number generator]] proposed in 1986 by [[Lenore Blum]], [[Manuel Blum]] and [[Michael Shub]].<ref name=blum1986> | |||
{{cite journal | |||
|last=Blum | |||
|first=Lenore | |||
|coauthors=Blum, Manuel; Shub, Mike | |||
|title=A Simple Unpredictable Pseudo-Random Number Generator | |||
|journal=SIAM Journal on Computing | |||
|date=1 May 1986 | |||
|volume=15 | |||
|issue=2 | |||
|pages=364–383 | |||
|doi=10.1137/0215025 | |||
|url=http://epubs.siam.org/doi/abs/10.1137/0215025}} | |||
</ref> | |||
Blum Blum Shub takes the form: | |||
:<math>x_{n+1} = x_n^2 \bmod M</math> | |||
where ''M''=''pq'' is the product of two large [[prime number|primes]] ''p'' and ''q''. At each step of the algorithm, some output is derived from ''x''<sub>''n''+1</sub>; the output is commonly either the [[parity bit|bit parity]] of ''x''<sub>''n''+1</sub> or one or more of the least significant bits of ''x''<sub>''n''+1''</sub>. | |||
The [[random seed|seed]] ''x''<sub>0</sub> should be an integer that is co-prime to ''M'' (i.e. ''p'' and ''q'' are not factors of ''x''<sub>0</sub>) and not 1 or 0. | |||
The two primes, ''p'' and ''q'', should both be [[Congruence relation|congruent]] to 3 (mod 4) (this guarantees that each [[quadratic residue]] has one [[square root]] which is also a quadratic residue) and [[greatest common divisor|gcd]]([[Euler's totient function|''φ'']](''p''-1), ''φ''(''q''-1)) should be small (this makes the cycle length large). | |||
An interesting characteristic of the Blum Blum Shub generator is the possibility to calculate any ''x''<sub>''i''</sub> value directly (via [[Euler's Theorem]]): | |||
:<math>x_i = \left( x_0^{2^i \bmod \lambda(M)} \right) \bmod M</math> | |||
where <math>\lambda</math> is the [[Carmichael function]]. (Here we have <math>\lambda(M) = \lambda(p\cdot q) = \operatorname{lcm}(p-1, q-1)</math>). | |||
==Security== | |||
The generator is very slow. However, there is a proof reducing its security to the [[Computational complexity theory|computational difficulty]] of the computing modular square roots, a problem whose difficulty is equivalent to factoring. When the primes are chosen appropriately, and [[big O notation|O]]([[logarithm|log]] log ''M'') lower-order bits of each ''x<sub>n</sub>'' are output, then in the limit as ''M'' grows large, distinguishing the output bits from random should be at least as difficult as factoring ''M''. | |||
==Example== | |||
Let <math>p=11</math>, <math>q=19</math> and <math>s=3</math> (where <math>s</math> is the seed.) We can expect to get a large cycle length for those small numbers, because <math>{\rm gcd}(\varphi(p-1), \varphi(q-1))=2</math>. | |||
The generator starts to evaluate <math>x_0</math> by using <math>x_{-1}=s</math> and creates the sequence <math>x_0</math>, <math>x_1</math>, <math>x_2</math>, <math>\ldots</math> <math>x_5</math> = 9, 81, 82, 36, 42, 92. The following table shows the output (in bits) for the different bit selection methods used to determine the output. | |||
{| class="wikitable" | |||
|- | |||
! Even parity bit | |||
! Odd parity bit | |||
! [[Least significant bit]] | |||
|- | |||
| 0 1 1 0 1 0 | |||
| 1 0 0 1 0 1 | |||
| 1 1 0 0 0 0 | |||
|} | |||
==References== | |||
{{Reflist}} | |||
;General | |||
* {{cite journal|last=Blum|first=Lenore|coauthors=Blum, Manuel; Shub, Mike|title=Comparison of Two Pseudo-Random Number Generators|series=Advances in Cryptology: Proceedings of CRYPTO '82|pages=61--78|publisher=Plenum|year=1982|url=http://www.iacr.org/cryptodb/data/paper.php?pubkey=1751}} | |||
* {{cite journal|last=Geisler|first=Martin|coauthors=Krøigård, Mikkel; Danielsen, Andreas|title=About Random Bits|date=December 2004|url=http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.90.3779}} available as [http://www.daimi.au.dk/~mg/mamian/random-bits.pdf PDF] and [http://daimi.au.dk/~mg/mamian/random-bits.ps.gz Gzipped Postscript] | |||
* | |||
==External links== | |||
* [http://web.archive.org/web/20090524070627/http://firefly.is-a-geek.org/gmpbbs/ GMPBBS] (archived 2009-05-24 at the [[Wayback Machine]]), a [[GNU General Public License|GPL]]'ed [[GNU Multi-Precision Library|GMP]]-based implementation of Blum Blum Shub by Mark Rossmiller. Retrieved 2011-09-05. | |||
* [http://code.google.com/p/javarng/ An implementation in Java] | |||
* [http://www.ciphersbyritter.com/NEWS2/TESTSBBS.HTM Randomness tests] | |||
[[Category:Pseudorandom number generators]] | |||
[[Category:Cryptographically secure pseudorandom number generators]] |
Revision as of 04:53, 3 February 2014
Template:More footnotes Template:Primary sources Blum Blum Shub (B.B.S.) is a pseudorandom number generator proposed in 1986 by Lenore Blum, Manuel Blum and Michael Shub.[1]
Blum Blum Shub takes the form:
where M=pq is the product of two large primes p and q. At each step of the algorithm, some output is derived from xn+1; the output is commonly either the bit parity of xn+1 or one or more of the least significant bits of xn+1.
The seed x0 should be an integer that is co-prime to M (i.e. p and q are not factors of x0) and not 1 or 0.
The two primes, p and q, should both be congruent to 3 (mod 4) (this guarantees that each quadratic residue has one square root which is also a quadratic residue) and gcd(φ(p-1), φ(q-1)) should be small (this makes the cycle length large).
An interesting characteristic of the Blum Blum Shub generator is the possibility to calculate any xi value directly (via Euler's Theorem):
where is the Carmichael function. (Here we have ).
Security
The generator is very slow. However, there is a proof reducing its security to the computational difficulty of the computing modular square roots, a problem whose difficulty is equivalent to factoring. When the primes are chosen appropriately, and O(log log M) lower-order bits of each xn are output, then in the limit as M grows large, distinguishing the output bits from random should be at least as difficult as factoring M.
Example
Let , and (where is the seed.) We can expect to get a large cycle length for those small numbers, because . The generator starts to evaluate by using and creates the sequence , , , = 9, 81, 82, 36, 42, 92. The following table shows the output (in bits) for the different bit selection methods used to determine the output.
Even parity bit | Odd parity bit | Least significant bit |
---|---|---|
0 1 1 0 1 0 | 1 0 0 1 0 1 | 1 1 0 0 0 0 |
References
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Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
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The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang - One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang available as PDF and Gzipped Postscript
External links
- GMPBBS (archived 2009-05-24 at the Wayback Machine), a GPL'ed GMP-based implementation of Blum Blum Shub by Mark Rossmiller. Retrieved 2011-09-05.
- An implementation in Java
- Randomness tests
- ↑
One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang