The North China Plain is a large-scale downfaulted rift basin formed in late Paleogene and Neogene and modified by the deposits of the Yellow River and is the largest alluvial plain of China. The plain is bordered to the north by the Yanshan Mountains, to the west by the Taihang Mountains, to the south by the Dabie and Tianmu Mountains, to the east by the Yellow Sea; the Yellow River flows through the middle of the plain into the Bohai Sea. Below the Sanmenxia Dam is the multipurpose Xiaolangdi Dam, located in the river's last valley before the North China Plain, a great delta created from silt dropped at the Yellow River's mouth over the millennia; the North China Plain extends over much of Henan and Shandong provinces, merges with the Yangtze Delta in northern Jiangsu and Anhui provinces. The Yellow River meanders over the fertile, densely populated plain emptying into the Bohai Sea; the plain is one of China's most important agricultural regions, producing corn, winter wheat and cotton. Its nickname is "Land of the yellow earth".

The southern part of the plain is traditionally referred to as the Central Plain, which formed the cradle of Chinese civilization. The plain covers an area of about 409,500 square kilometers, most of, less than 50 metres above sea level; this flat yellow-soil plain is the main area of sorghum, millet and cotton production in China. Wheat, sesame seed, peanuts are grown here; the plain is one of the most densely populated regions in the world. Beijing, the national capital, is located on the northeast edge of the plain, with Tianjin, an important industrial city and commercial port, near its northeast coast. Shengli Oil Field in Shandong is an important petroleum base; the geography of the North China Plain has had profound political implications. Unlike areas to the south of the Yangtze, the plain runs uninterrupted by mountains and has far fewer rivers, as a result communication by horse is rapid within the plain; as a result, the spoken language is uniform in contrast to the plethora of languages and dialects in southern China.

In addition the possibility of rapid communication has meant that the political center of China has tended to be located here. Because the fertile soil of the North China Plain merges with the steppes and deserts of Dzungaria, Inner Mongolia, Northeast China, the plain has been prone to invasion from nomadic or semi-nomadic ethnic groups originating from those regions, prompting the construction of the Great Wall of China. Although the soil of the North China Plain is fertile, the weather is unpredictable, being at the intersection of humid winds from the Pacific and dry winds from the interior of the Asian continent; this makes the plain prone to drought. Moreover, the flatness of the plain promotes massive flooding. Many historians have proposed that these factors have encouraged the development of a centralized Chinese state to manage granaries, maintain hydraulic works, administer fortifications against the steppe peoples. Encyclopædia Britannica: "North China Plain"

A cryptographically secure pseudorandom number generator or cryptographic pseudorandom number generator is a pseudorandom number generator with properties that make it suitable for use in cryptography. It is loosely known as a cryptographic random number generator. Most cryptographic applications require random numbers, for example: key generation nonces salts in certain signature schemes, including ECDSA, RSASSA-PSSThe "quality" of the randomness required for these applications varies. For example, creating a nonce in some protocols needs only uniqueness. On the other hand, the generation of a master key requires a higher quality, such as more entropy, and in the case of one-time pads, the information-theoretic guarantee of perfect secrecy only holds if the key material comes from a true random source with high entropy, thus any kind of pseudo-random number generator is insufficient. Ideally, the generation of random numbers in CSPRNGs uses entropy obtained from a high-quality source the operating system's randomness API.

However, unexpected correlations have been found in several such ostensibly independent processes. From an information-theoretic point of view, the amount of randomness, the entropy that can be generated, is equal to the entropy provided by the system, but sometimes, in practical situations, more random numbers are needed than there is entropy available. The processes to extract randomness from a running system are slow in actual practice. In such instances, a CSPRNG can sometimes be used. A CSPRNG can "stretch" the available entropy over more bits; the requirements of an ordinary PRNG are satisfied by a cryptographically secure PRNG, but the reverse is not true. CSPRNG requirements fall into two groups: first; every CSPRNG should satisfy the next-bit test. That is, given the first k bits of a random sequence, there is no polynomial-time algorithm that can predict the th bit with probability of success non-negligibly better than 50%. Andrew Yao proved in 1982 that a generator passing the next-bit test will pass all other polynomial-time statistical tests for randomness.

Every CSPRNG should withstand "state compromise extensions". In the event that part or all of its state has been revealed, it should be impossible to reconstruct the stream of random numbers prior to the revelation. Additionally, if there is an entropy input while running, it should be infeasible to use knowledge of the input's state to predict future conditions of the CSPRNG state. Example: If the CSPRNG under consideration produces output by computing bits of π in sequence, starting from some unknown point in the binary expansion, it may well satisfy the next-bit test and thus be statistically random, as π appears to be a random sequence. However, this algorithm is not cryptographically secure. Most PRNGs will fail on both counts. First, while most PRNGs outputs appear random to assorted statistical tests, they do not resist determined reverse engineering. Specialized statistical tests may be found specially tuned to such a PRNG that shows the random numbers not to be random. Second, for most PRNGs, when their state has been revealed, all past random numbers can be retrodicted, allowing an attacker to read all past messages, as well as future ones.

CSPRNGs are designed explicitly to resist this type of cryptanalysis. In the asymptotic setting, a family of deterministic polynomial time computable functions G k: k → p for some polynomial p, is a pseudorandom number generator, if it stretches the length of its input, if its output is computationally indistinguishable from true randomness, i.e. for any probabilistic polynomial time algorithm A, which outputs 1 or 0 as a distinguisher, | Pr x ← k − Pr r ← p | < μ for some negligible function μ. There is an equivalent characterization: For any function family G k: k

Voorhees High School is a four-year public high school located in Lebanon Township, New Jersey, named for Foster McGowan Voorhees, the 30th Governor of New Jersey. It is one of two high schools in the North Hunterdon-Voorhees Regional High School District, serving students in ninth through twelfth grades from six municipalities in northern Hunterdon County, New Jersey, United States; the school has been accredited by the Middle States Association of Colleges and Schools Commission on Secondary Schools since 1977. Students come from the sending districts of Califon, Glen Gardner, Hampton Borough, High Bridge, Lebanon Township and Tewksbury; as of the 2015-16 school year, the school had an enrollment of 1,080 students and 86.2 classroom teachers, for a student–teacher ratio of 12.5:1. There were 7 eligible for reduced-cost lunch. In 2015, Voorhees High School was one of 15 schools in New Jersey, one of nine public schools, recognized as a National Blue Ribbon School in the exemplary high performing category by the United States Department of Education.

In its listing of "America's Best High Schools 2016", the school was ranked 233rd out of 500 best high schools in the country. In the 2011 "Ranking America's High Schools" issue by The Washington Post, the school was ranked 24th in New Jersey and 830th nationwide. In Newsweek's May 22, 2007, ranking the country's top high schools, Voorhees High School was listed in 1118th place, the 36th-highest ranked school in New Jersey; the school was the 43rd-ranked public high school in New Jersey out of 339 schools statewide in New Jersey Monthly magazine's September 2014 cover story on the state's "Top Public High Schools", using a new ranking methodology. The school had been ranked 48th in the state of 328 schools in 2012, after being ranked 59th in 2010 out of 322 schools listed; the magazine ranked the school 41st in 2008 out of 316 schools. The school was ranked 30th in the magazine's September 2006 issue, which included 316 schools across the state. Schooldigger.com ranked the school tied for 83rd out of 381 public high schools statewide in its 2011 rankings which were based on the combined percentage of students classified as proficient or above proficient on the mathematics and language arts literacy components of the High School Proficiency Assessment.

The school was the Consumer Bowl 2006 and 2007 state champion, a program that evaluates the skills of students as informed consumers. Voorhees High School Vikings compete in the Skyland Conference, composed of public and parochial high schools in Hunterdon County, Somerset County and Warren County in west central New Jersey; the conference operates under the jurisdiction of the New Jersey State Interscholastic Athletic Association. With 778 students in grades 10-12, the school was classified by the NJSIAA for the 2015-16 school year as North II, Group III for most athletic competition purposes, which included schools with an enrollment of 778 to 1,062 students in that grade range. Voorhees approved a plan in 2010 for construction of an $850,000 artificial turf field to be be used for football. Voorhees' football team was unable to use its grass field between 2008 and 2009 when glass shards and other debris was found in the turf; the wrestling team won the Central Jersey Group II state sectional championship in 1980-1982, 1995, 1996 and 1998.

The team won the state Group II title in 1982 and 1995, the Group III title in 1985 and 1987. The program's 15 sectional titles are the seventh-most of any public high school in the state; the boys' cross country team won the Group II state championship in 1981-1983 and 2000. The baseball team won the Group III state championship in 1984, defeating Ramsey High School in the tournament final; the team won the 1998 Central Jersey Group II state sectional championship, defeating Raritan High School by a score of 1-0 in the first round and Manasquan High School by 4-1 in the semifinals, before defeating Carteret High School 8-2 in the tournament final. They lost 1-0 to a nationally ranked Audubon High School team in extra innings on a controversial call at the plate to end their playoff run in the Group II championship; the field hockey team won the Central Jersey Group II state sectional championship in 1993 and 1996, won the North II Group II title in 1999, 2000, 2002 and 2006. Voorhees High School's football team competes in an annual Milk Can Game against rival North Hunterdon High School.

After the conclusion of the game, a golden milk can is awarded to the winner, which earns bragging rights and ownership of the can until the next year's game. The 36th annual Milk Can Game was played in November 2011, with Voorhees winning at home by a score of 13-7 to end a five-year streak by North Hunterdon. With a 14-7 win in 2018, North Hunterdon has won seven consecutive games in the series and holds an overall record of 30-12-1 in the 43 Milk Can games played between the two schools; the 1995 Voorhees football team won the Central Jersey Group II state championship. The girls' track team won the Group II indoor relay championship in 2001; the field hockey team won the 2002 North II, Group II sectional championship, edging Madison High School 3-2 in the final game. The 2006 team won the North Group III tournament with a 1-0 win over Ocean Township High School; the girls' basketball team won the 2000 Central, Group II title over Delaware Valley Regional High School, 62-42. The boys fencing team has won three state titles, most in 2005 w