en>Rjwilmsi: /* References */Journal cites, added 1 PMID, added 1 PMC using AWB (10482)

2014-11-02T10:33:03Z

References: Journal cites, added 1 PMID, added 1 PMC using AWB (10482)

← Older revision		Revision as of 12:33, 2 November 2014
Line 1:		Line 1:
	~~In [[cryptography]], a '''preimage attack'''~~ on ~~[[cryptographic hash function]]s tries to find~~ a ~~[[message]] that has a specific hash value~~. ~~A cryptographic hash function should resist attacks on its [[Preimage#Inverse image\|preimage]]~~.		Statistics from the Urban Redevelopment Authority (URA) on Friday showed a 1.3 per cent decline in prices within the first quarter of this year. It's the largest drop since the second quarter of 2009, when prices fell by four.7 per cent.<br><br>What's non restricted residential property underneath the Residential Property Act SINGAPORE - As property costs in Singapore continue to tumble, one of many country's greatest developers posted disappointing earnings whereas one other said it would raise capital to guard itself in opposition to the downturn. The builders are pushed by the promise of higher yield, he stated. OCBC's mortgage guide in London has fattened about 5 times since 2010, given the curiosity in residential and commercial properties from Singapore builders. Listed property developers in Singapore have introduced plans to develop into these two markets, given pressures on dwelling ground. www.Bedok-Condos.com (latest new launch at BedokCentral City Centre and Bedok Reservoir) Residential or non-residential property<br><br>Ho Bee is another candidate on the high of our record, given its engaging valuation, majority shareholder and strong stability sheet with limited want for fairness fundraising. On top of that, we observed that Ho Bee Holdings (owned by Mr Chua Thian Poh, Mdm Ng Noi Hinoy and Mr Chua Kong Chian) has been increasing its stake since 70.eight% in Apr 2013 to 72.6%. Bukit Sembawang matches the factors of low cost valuation, low liquidity and restricted want for fairness fundraising. Nevertheless, privatisation will not be a near-term theme for the stock as the most important shareholder owns only forty one 41% of the corporate and doesn't face a push issue such because the extension cost. Industrial Gear Diploma in Estate Administration or equivalent Senior/Advertising & Promotion Govt<br><br>Fixtures are important. These embrace the in-built wardrobe and cabinets. We will inspect these fixtures in the show flat to evaluate the overall workmanship. The brands and firms that make the fixtures are vital as properly. Increasingly, numerous developers are using cheaper local/Asian companies, as typically homebuyers do not seem to thoughts since the brand names are normally not indicated, and sometimes the workmanship could be missing. The forms of supplies, furnishing, fitting, appliances, and so forth. for use or offered are offered on this list in the S&P agreement. Anything more that you simply managed to discount from the developer (good job) needs to be within the form of a written affirmation. Discounts Bukit Sembawang Estates Limited Shenton Method , Singapore<br><br>The Company is committed to develop its industrial portfolio in key Asian cities. Its portfolio of abroad business properties includes Seasons Metropolis in the Sino-Singapore Tianjin Eco-City, a Grade A office development in Beijing and a retail mall Life Hub @ Jinqiao in Shanghai, China, Saigon Centre in Ho Chi Minh Metropolis, Vietnam, as well as Worldwide Monetary Centre Jakarta in Indonesia. The Company also plans to develop Park Avenue Central in Shanghai right into a retail-cum-office complex.<br><br>We use cookies to make sure that we provde the best experience on our web site. Should you proceed without changing your browser settings, we'll assume that you are completely satisfied to receive all cookies on the Knight Frank web site. Discover out extra about how Knight Frank makes use of cookies Accomplished in April 2009, The Coast boasts 249 units of three- and four-bedroom apartments as well as luxury penthouses, 41 personal berthing facilities and views of the South China Sea. It's considered one of Ho Bee's five developments on the exclusive enclave of Sentosa Cove.<br><br>Subsequent 12 months there will be fairly a no. of recent mission launches that can sooth the market. Whether or not to purchase now or later will also relies on which mission / district you are taking a look at and the transactions happening for that area. I think the subprime crisis within the U.S., the ensuing credit score crunch and a u.s. recession will dent the property market in Singapore for a solid two-three years. After that, it would resume its upward trend and hit levels close to what we see in Hong Kong, New York and London. I'd wait. Properties that do not fall throughout the definition of residential properties said above are non-residential properties JOOL SUITES PRIVATE CONDOMINIUM [http://www.we-r1-one.com/activity/p/209079/ house in singapore] SING JOO WALK, FARRER PARK (DISTRICT 08) IP Real Property Investments Pte Ltd CapitaLand Limited<br><br>The way it works is assuming the gross plot ratio is 1.4, and the developer bought a land of size a hundred,000 sq. feet. They will thus construct as much as a most of 1.4 a hundred,000 = 140,000 sq. feet worth of apartments to promote. (That total figure of a hundred and forty,000 sq. ft known as the gross flooring area, GFA) The one authorized representations are those info included within the brochure/reality sheet/Sales &Purchase settlement. Even then some specs should not included in it, like how thick the partitions are. Check with the brokers and get them to put in writing it down if possible. It is to developer's interest to maintain unit prices excessive on paper. Sometimes to take action they provide furniture vouchers. Completion of car park, roads and drains serving the housing undertaking Frasers Centrepoint Limited

	In the ~~context~~ of ~~attack~~, ~~there are two types of preimage resistance:~~

	* '~~'preimage resistance'': for essentially all pre~~-~~specified outputs~~, it ~~is computationally infeasible~~ to ~~find any input which hashes~~ to ~~that output~~, i.e., ~~to find any preimage ''x''′ such that ''h''(''x''′) = ''y'' when~~ given ~~any ''y'' for which a corresponding input is not known~~.~~<ref name="crypto~~-~~hash~~-~~def"~~>
	~~{{cite paper \|last1= Rogaway \|first1= P. \|last2= Shrimpton \|first2= T. \|title= Cryptographic Hash-Function Basics: Definitions~~, ~~Implications~~, and ~~Separations~~ for ~~Preimage Resistance~~, ~~Second-Preimage Resistance~~, and ~~Collision Resistance\|journal= Fast Software Encryption (2004~~) ~~\|publisher= Springer-Verlag\|url= http://www~~.cs.~~ucdavis~~.~~edu/~rogaway/papers/relates~~.~~pdf\|accessdate=17 November 2012}}~~
	~~</ref>~~
	* ''second-~~preimage resistance'': it is computationally infeasible to find any second input which has~~ the ~~same output~~ as ~~any specified input, i.e., given ''x'~~'~~, to find~~ a ~~second preimage ''x''' ≠ ''x''~~ such ~~that ''h''(''x'') = ''h''(''x''′)~~.<~~ref name="crypto-hash-def" /~~>

	These ~~can be compared with a [[collision resistance]],~~ in ~~which it is computationally infeasible~~ to ~~find any two distinct inputs ''x''~~, ~~''x''′ which hash~~ to the ~~same output~~, i.e.~~, such~~ that ~~''h''~~(~~''x'') = ''h''(''x''′~~).<~~ref name="crypto~~-~~hash~~-~~def" />~~

	~~Collision resistance implies second-preimage resistance~~,~~<ref name="crypto~~-~~hash~~-~~def" /~~> ~~but does not guarantee preimage resistance~~.~~<ref name="crypto~~-~~hash~~-~~def" />~~

	~~== Applied preimage attacks ==~~
	~~By definition~~, ~~an ideal hash function is such that~~ the ~~fastest way to compute a first or second preimage is through a [[brute force attack]]~~. ~~For an~~ ''~~n''-bit hash, this attack has a [[time complexity]]~~ <~~math~~>~~2^n~~<~~/math~~>~~, which is considered too high for~~ a ~~typical output size~~ of ~~''n'' = 64 bits~~. ~~If such complexity is~~ the ~~best~~ that ~~can be achieved by an adversary~~, ~~then~~ the ~~hash function is considered preimage~~-~~resistant~~.

	~~Faster preimage attacks can be found by [[cryptanalysis\|cryptanalysing]] certain hash functions~~, and ~~are specific~~ to that ~~function~~. ~~Some significant preimage attacks have already been discovered~~, ~~but they are not yet practical~~. If a ~~practical preimage attack is discovered~~, ~~it would drastically affect many Internet protocols~~. ~~In this case, "practical" means that it could be executed by an attacker with~~ a ~~reasonable amount~~ of ~~resources~~. ~~For example~~, ~~a preimaging attack that costs trillions~~ of ~~dollars and takes decades~~ to ~~preimage one desired hash value or one message is not practical; one that costs~~ a ~~few thousand dollars~~ and ~~takes a few weeks might be very practical~~.

	~~All currently~~ known ~~practical or almost-practical attacks on [[MD5]] and [[SHA-1]]~~ are ~~[[collision attack]]s~~.~~{{Citation needed\|reason=It appears MD5 is suffering 2nd-preimage attacks~~. ~~See Talk page~~ and ~~''This article needs help''\|date=November 2012}} In general, a collision attack is easier~~ to ~~mount than a preimage attack, as~~ it is ~~not restricted by any set value (any two values can be used~~ to ~~collide)~~. ~~The time complexity~~ of the ~~collision attack, in contrast, is <math>2^{\frac{n}{2}}.</math>~~

	~~== See also ==~~
	* [[Birthday attack]]
	* [[Cryptographic hash function]]
	* [[Rainbow table]]
	* [[Random oracle]]

	~~== References ==~~
	* IETF RFC 4270: Attacks on Cryptographic Hashes in Internet Protocols
	~~<references />~~

	~~{{cryptography navbox \| hash}}~~

	~~{{DEFAULTSORT:Preimage Attack}}~~
	~~[[Category:Cryptographic attacks]]~~

	~~{{crypto-stub}}~~

en>Denniss: (Script) File renamed: File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv.ogg → File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv

2014-01-19T17:20:07Z

(Script) File renamed: File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv.ogg → File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv

New page

In [[cryptography]], a '''preimage attack''' on [[cryptographic hash function]]s tries to find a [[message]] that has a specific hash value. A cryptographic hash function should resist attacks on its [[Preimage#Inverse image|preimage]].

In the context of attack, there are two types of preimage resistance:

* ''preimage resistance'': for essentially all pre-specified outputs, it is computationally infeasible to find any input which hashes to that output, i.e., to find any preimage ''x''′ such that ''h''(''x''′) = ''y'' when given any ''y'' for which a corresponding input is not known.<ref name="crypto-hash-def">
{{cite paper |last1= Rogaway |first1= P. |last2= Shrimpton |first2= T. |title= Cryptographic Hash-Function Basics: Definitions, Implications, and Separations for Preimage Resistance, Second-Preimage Resistance, and Collision Resistance|journal= Fast Software Encryption (2004) |publisher= Springer-Verlag|url= http://www.cs.ucdavis.edu/~rogaway/papers/relates.pdf|accessdate=17 November 2012}}
</ref>
* ''second-preimage resistance'': it is computationally infeasible to find any second input which has the same output as any specified input, i.e., given ''x'', to find a second preimage ''x''' ≠ ''x'' such that ''h''(''x'') = ''h''(''x''′).<ref name="crypto-hash-def" />

These can be compared with a [[collision resistance]], in which it is computationally infeasible to find any two distinct inputs ''x'', ''x''′ which hash to the same output, i.e., such that ''h''(''x'') = ''h''(''x''′).<ref name="crypto-hash-def" />

Collision resistance implies second-preimage resistance,<ref name="crypto-hash-def" /> but does not guarantee preimage resistance.<ref name="crypto-hash-def" />

== Applied preimage attacks ==
By definition, an ideal hash function is such that the fastest way to compute a first or second preimage is through a [[brute force attack]]. For an ''n''-bit hash, this attack has a [[time complexity]] <math>2^n</math>, which is considered too high for a typical output size of ''n'' = 64 bits. If such complexity is the best that can be achieved by an adversary, then the hash function is considered preimage-resistant.

Faster preimage attacks can be found by [[cryptanalysis|cryptanalysing]] certain hash functions, and are specific to that function. Some significant preimage attacks have already been discovered, but they are not yet practical. If a practical preimage attack is discovered, it would drastically affect many Internet protocols. In this case, "practical" means that it could be executed by an attacker with a reasonable amount of resources. For example, a preimaging attack that costs trillions of dollars and takes decades to preimage one desired hash value or one message is not practical; one that costs a few thousand dollars and takes a few weeks might be very practical.

All currently known practical or almost-practical attacks on [[MD5]] and [[SHA-1]] are [[collision attack]]s.{{Citation needed|reason=It appears MD5 is suffering 2nd-preimage attacks. See Talk page and ''This article needs help''|date=November 2012}} In general, a collision attack is easier to mount than a preimage attack, as it is not restricted by any set value (any two values can be used to collide). The time complexity of the collision attack, in contrast, is <math>2^{\frac{n}{2}}.</math>

== See also ==
* [[Birthday attack]]
* [[Cryptographic hash function]]
* [[Rainbow table]]
* [[Random oracle]]

== References ==
* IETF RFC 4270: Attacks on Cryptographic Hashes in Internet Protocols
<references />

{{cryptography navbox | hash}}

{{DEFAULTSORT:Preimage Attack}}
[[Category:Cryptographic attacks]]

{{crypto-stub}}

Writhe - Revision history

en>Rjwilmsi: /* References */Journal cites, added 1 PMID, added 1 PMC using AWB (10482)

en>Denniss: (Script) File renamed: File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv.ogg → File:Simulation of an elastic rod relieving torsional stress by forming coils.ogv