fer论文范文

fer论文范文

我们知道，格什温最初就是一个很出色的钢琴家。1925年他亲自演奏了《蓝色狂想曲》的钢琴版，并且留下一个相当不错，足够清晰的录音。因而到了70年代，托马斯另辟蹊径，指挥乐队为这个钢琴版录音配上了管弦乐，配得丝纹不差，很能以“假”乱真。听起来，它比我们通常听到的历时15分钟以上的《蓝色狂想曲》演奏得快些，只有13分钟。你或许不大习惯这速度，而我也不敢肯定它更符合格什温本意，毕竟当他独奏钢琴时是并不需要给乐队发挥留出时间余地的。不过，我倒敢说，比起速度正常，而且也是极为精彩的伯恩斯坦的名演奏（SONY SMK 42264），托马斯的这张爵士味更足，乐队的配合显得更洒脱些.
George Gershwin (1898-1937), 美国著名作曲家，生于纽约布鲁克林，曾广泛接触和研究通俗音乐领域的 各种体裁风格，写过大量的流行歌曲和数十部歌舞表演、音乐剧，是百老汇舞台 和好莱坞的名作曲家。
1924年为保尔·怀特曼的爵士音乐会写了《蓝色狂想曲》获得巨大成功，影响了 美国和其他国家的作曲家在作品中运用爵士的手法。接着，创作了管弦乐曲《一个美国人在巴黎》、 《第二狂想曲》、《古巴序曲》，并以描写黑人生活的歌剧《波基与贝丝》达到创作的顶点。 格什温的卓越贡献是把德彪西和拉赫玛尼诺夫的风格与美国的爵士乐风格结合了起来，虽缺乏熟练的 写作技巧，却是个了不起的旋律天才。他的歌曲总是活泼有趣，温柔清新；大型乐曲则节奏明快， 和声优美，富于幽默感，既有独特的个性，又是典型的美国风格，因而具有持久的艺术魅力。 1937年夏因脑癌去世，年仅三十九岁。 [ 格什温、《蓝色狂想曲》与格罗菲 ] 在乔治·格什温的代表作《蓝色狂想曲》里，可以找到美国爵士音乐和感伤音乐在节奏上、旋律上 与和声上最好的扩展运用。格什温梦想着把建立在爵士乐上的感伤歌曲带进美国音乐厅里来。他的第一首 音乐会型的作品《蓝色狂想曲》是以李斯特的《匈牙利狂想曲》为模型的，就是说，是为了用全部 交响乐队伴奏的钢琴独奏而写的。 格什温后来学习了配器法，以便能为自己的音乐作品创作出他认为最有效果的器乐部分，但是 对于《蓝色狂想曲》，他却请来一个熟练的改编者来编谱。这个改编者就是美国著名作曲家 菲尔德·格罗菲（Ferde Grofe），这个人后来用他配器的才能来为他自己的某些作品写作—— 大多数是美国场面的音画。他的《大峡谷组曲》可谓用来表现大自然的色彩和情调感的一个令人目眩的 乐器调色展览会。

有关于三基色（红绿蓝）合成白光的这方面的英文论文。

Primary colors are sets of colors that can be combined to make a useful range of colors. For human applications, three primary colors are usually used, since human color vision is trichromatic.

For additive combination of colors, as in overlapping projected lights or in CRT displays, the primary colors normally used are red, green, and blue. For subtractive combination of colors, as in mixing of pigments or dyes, such as in printing, the primaries normally used are cyan, magenta, and yellow,[1] though the set of red, yellow, blue is popular among artists.[2] See RGB color model, CMYK color model, and RYB color model for more on these popular sets of primary colors.

Any choice of primary colors is essentially arbitrary; for example, an early color photographic process, autochrome, typically used orange, green, and violet primaries.[3]

The most commonly used additive color primaries are the secondary colors of the most commonly used subtractive color primaries, and vice versa.

Primary colors are not a fundamental property of light but are often related to the physiological response of the eye to light. Fundamentally, light is a continuous spectrum of the wavelengths that can be detected by the human eye, an infinite-dimensional stimulus space.[4] However, the human eye normally contains only three types of color receptors, called cone cells. Each color receptor responds to different ranges of the color spectrum. Humans and other species with three such types of color receptors are known as trichromats. These species respond to the light stimulus via a three-dimensional sensation, which generally can be modeled as a mixture of three primary colors.[4]

Before the nature of colorimetry and visual physiology were well understood, scientists such as Thomas Young, James Clark Maxwell, and Hermann von Helmholtz expressed various opinions about what should be the three primary colors to describe the three primary color sensations of the eye.[5] Young originally proposed red, green, and violet, and Maxwell changed violet to blue; Helmholtz proposed "a slightly purplish red, a vegetation-green, slightly yellowish (wave-length about 5600 tenth-metres), and an ultramarine-blue (about 4820)".[6] In modern understanding, the human cone cells do not correspond to any real primary colors.

Species with different numbers of receptor cell types would have color vision requiring a different number of primaries. For example, for species known as tetrachromats, with four different color receptors, one would use four primary colors. Since humans can only see to 400 nanometers (violet), but tetrachromats can see into the ultraviolet to about 300 nanometers, this fourth primary color might be located in the shorter-wavelength range.

Many birds and marsupials are tetrachromats, and it has been suggested that some human females are tetrachromats as well[7][8], having an extra variant version of the long-wave (L) cone type.[9] The peak response of human color receptors varies, even among individuals with "normal" color vision[10]; in non-human species this polymorphic variation is even greater, and it may well be adaptive[11]. Most mammals other than primates have only two types of color receptors and are therefore dichromats; to them, there are only two primary colors.

It would be incorrect to assume that the world "looks tinted" to an animal (or human) with anything other than the human standard of three color receptors. To an animal (or human) born that way, the world would look normal to it, but the animal's ability to detect and discriminate colors would be different from that of a human with normal color vision. If a human and an animal both look at a natural color, they see it as natural; however, if both look at a color reproduced via primary colors, such as on a color television screen, the human may see it as matching the natural color, while the animal does not; in this sense, reproduction of color via primaries must be "tuned" to the color vision system of the observer.

Media that combine emitted lights to create the sensation of a range of colors are using the additive color system. Typically, the primary colors used are red, green, and blue.[12]

Television and other computer and video displays are a common example of the use of additive primaries and the RGB color model. The exact colors chosen for the primaries are a technological compromise between the available phosphors (including considerations such as cost and power usage) and the need for large color triangle to allow a large gamut of colors. The ITU-R BT.709-5/sRGB primaries are typical.

CIE 1931 RGB color triangle with monochromatic primariesAdditive mixing of red and green light produces shades of yellow, orange, or brown.[13] Mixing green and blue produces shades of cyan, and mixing red and blue produces shades of purple, including magenta. Mixing nominally equal proportions of the additive primaries results in shades of grey or white; the color space that is generated is called an RGB color space.

The CIE 1931 color space defines monochromatic primary colors with wavelengths of 435.8 nm (violet), 546.1 nm (green) and 700 nm (red). The corners of the color triangle are therefore on the spectral locus, and the triangle is about as big as it can be. No real display device uses such primaries, as the extreme wavelengths used for violet and red result in a very low luminous efficiency.

Traditional
Main article: RYB color model
RYB (red, yellow, and blue) is a historical set of subtractive primary colors. It is primarily used in art and art education, particularly painting.[14] It predates modern scientific color theory.

Standard RYB Color WheelRYB make up the primary color triad in a standard color wheel; the secondary colors VOG (violet, orange, and green) make up another triad. Triads are formed by 3 equidistant colors on a particular color wheel; neither RYB nor VOG is equidistant on a perceptually uniform color wheel, but rather have been defined to be equidistant in the RYB wheel.[15]

Painters have long used more than three "primary" colors in their palettes—and at one point considered red, yellow, blue, and green to be the four primaries[16]. Red, yellow, blue, and green are still widely considered the four psychological primary colors,[17] though red, yellow, and blue are sometimes listed as the three psychological primaries [18], with black and white occasionally added as a fourth and fifth [19].

During the 18th century, as theorists became aware of Isaac Newton’s scientific experiments with light and prisms, red, yellow, and blue became the canonical primary colors—supposedly the fundamental sensory qualities that are blended in the perception of all physical colors and equally in the physical mixture of pigments or dyes. This theory became dogma, despite abundant evidence that red, yellow, and blue primaries cannot mix all other colors, and has survived in color theory to the present day.[20]

Using red, yellow, and blue as primaries yields a relatively small gamut, in which, among other problems, colorful greens, cyans, and magentas are impossible to mix, because red, yellow, and blue are not well-spaced around a perceptually uniform color wheel. For this reason, modern three- or four-color printing processes, as well as color photography, use cyan, yellow, and magenta as primaries instead.[21] Most painters include colors in their palettes which cannot be mixed from yellow, red, and blue paints, and thus do not fit within the RYB color model. Some who do use a three-color palette opt for the more evenly spaced cyan, yellow, and magenta used by printers, and others paint with 6 or more colors to widen their gamuts.[22] The cyan, magenta, and yellow used in printing are sometimes known as "process blue," "process red," "process yellow."[23]

[edit] CMYK color model, or four-color printing
Main article: CMYK color model
In the printing industry, to produce the varying colors the subtractive primaries cyan, magenta, and yellow are applied together in varying amounts. Before the color names cyan and magenta were in common use, these primaries were often known as blue-green and purple, or in some circles as blue and red, respectively, and their exact color has changed over time with access to new pigments and technologies.[24]

Subtractive color mixing – the magenta and cyan primaries are sometimes called purple and blue-green, or red and blueMixing yellow and cyan produces green colors; mixing yellow with magenta produces reds, and mixing magenta with cyan produces blues. In theory, mixing equal amounts of all three pigments should produce grey, resulting in black when all three are applied in sufficient density, but in practice they tend to produce muddy brown colors. For this reason, and to save ink and decrease drying times, a fourth pigment, black, is often used in addition to cyan, magenta, and yellow.

The resulting model is the so-called CMYK color model. The abbreviation stands for cyan, magenta, yellow, and key—black is referred to as the key color, a shorthand for the key printing plate that impressed the artistic detail of an image, usually in black ink.[25]

In practice, colorant mixtures in actual materials such as paint tend to be more complex. Brighter or more saturated colors can be created using natural pigments instead of mixing, and natural properties of pigments can interfere with the mixing. For example, mixing magenta and green in acrylic creates a dark cyan—something which would not happen if the mixing process were perfectly subtractive.

In the subtractive model, adding white to a color, whether by using less colorant or by mixing in a reflective white pigment such as zinc oxide, does not change the color’s hue but does reduce its saturation. Subtractive color printing works best when the surface or paper is white, or close to it.

A system of subtractive color does not have a simple chromaticity gamut analogous to the RGB color triangle, but a gamut that must be described in three dimensions. There are many ways to visualize such models, using various 2D chromaticity spaces or in 3D color spaces

Notes and references
^ Matthew Luckiesh (1915). Color and Its Applications. D. Van Nostrand company. pp. 58, 221. books?id=0BgCAAAAYAAJ&pg=RA1-PA221&dq=magenta+cyan+yellow+date:0-1923+printing&as_brr=1.
^ Chris Grimley and Mimi Love (2007). Color, space, and style: all the details interior designers need to know but can never find. Rockport Publishers. p. 137. ISBN 9781592532278. books?id=uVxa-_N4LQ4C&pg=PA137&dq=ryb+color+model+paint&lr=&as_brr=3&ei=AFbaSq-1AY6GlQThiayTAQ#v=onepage&q=ryb%20color%20model%20paint&f=false.
^ Walter Hines Page and Arthur Wilson Page (1908). The World's Work: Volume XV: A History of Our Time. Doubleday, Page & Company. books?id=hKPvxXgBN1oC&pg=PA9508&dq=autochrome+orange+violet+green&as_brr=1.
^ a b Michael I. Sobel (1989). Light. University of Chicago Press. pp. 52–62. ISBN 0226767515. books?id=PDmAdQpmxl8C&pg=PA58&ots=nx4W7J2aTc&dq=spectrum+color+infinite-dimensional+cones&sig=uM9RwCK7fFquO9e2oz-79xjbe8w#PPA59,M1.
^ Edward Albert Sharpey-Schäfer (1900). Text-book of physiology. 2. Y. J. Pentland. p. 1107. books?id=fz0uAAAAYAAJ&pg=PA1107&dq=primary+red-green-and-violet+maxwell+sensation&as_brr=3&ei=ew1NSpvYJpXUlQTZ4Iwe&client=firefox-a.
^ Alfred Daniell (1904). A text book of the principles of physics. Macmillan and Co. p. 575. books?id=oPQZAAAAYAAJ&pg=PA575&dq=primary+red-green-and-violet+maxwell&as_brr=3&ei=8QpNSsT5KYzkkwTDvNwj&client=firefox-a.
^ Backhaus, Kliegl & Werner "Color vision, perspectives from different disciplines" (De Gruyter, 1998), pp.115-116, section 5.5.
^ Pr. Mollon (Cambridge university), Pr. Jordan (Newcastle university) "Study of women heterozygote for colour difficiency" (Vision Research, 1993)
^ M. Neitz, T. W. Kraft, and J. Neitz (1998). "Expression of L cone pigment gene subtypes in females". Vision Research 38: 3221–3225. doi:10.1016/S0042-6989(98)00076-5.
^ Neitz, Jay & Jacobs, Gerald H. (1986). "Polymorphism of the long-wavelength cone in normal human colour vision." Nature. 323, 623-625.
^ Jacobs, Gerald H. (1996). "Primate photopigments and primate color vision." PNAS. 93 (2), 577–581.
^ Thomas D. Rossing and Christopher J. Chiaverina (1999). Light science: physics and the visual arts. Birkhäuser. p. 178. ISBN 9780387988276. books?id=jpH1_dCT_UcC&pg=PA178&dq=red+green+blue+additive+color+primaries+violet&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&as_brr=3&ei=DCtMSueTFIL6lQSApbEU.
^ "Some Experiments on Color", Nature 111, 1871, in John William Strutt (Lord Rayleigh) (1899). Scientific Papers. University Press. books?id=KWMSAAAAIAAJ&pg=PA84&dq=date:0-1923+light+red+green+yellow-or-orange&as_brr=1#PPA85,M1.
^ Tom Fraser and Adam Banks (2004). Designer’s Color Manual: The Complete Guide to Color Theory and Application. Chronicle Books. ISBN 081184210X. books?id=WXZNPaX-LvcC&pg=PA27&ots=HShXs43Vb9&dq=red-yellow-blue+color+mixing&ei=Q5C7RpKQBaPKowLOzbnwBQ&sig=tzY-Dg0Vd2qsvzkAED_4kTV_AYE.
^ Stephen Quiller (2002). Color Choices. Watson–Guptill. ISBN 0823006972. books?id=jiUTZQj_v5QC&pg=PA12&ots=uIkYShJkkF&dq=what-is-a-color-wheel+spaced+red+yellow+blue&ei=PfO7RtDOOaDeoALSidXvBQ&sig=nKVzb_VaCzhkW5LkewElB4laG90.
^ For instance Leonardo da Vinci wrote of these four simple colors in his notebook circa 1500. See Rolf Kuenhi. “Development of the Idea of Simple Colors in the 16th and Early 17th Centuries”. Color Research and Application. Volume 32, Number 2, April 2007.
^ Resultby Leslie D. Stroebel, Ira B. Current (2000). Basic Photographic Materials and Processes. Focal Press. ISBN 0240803450. books?id=BRYa6Qpsw48C&pg=PP1&dq=Basic+Photographic+Materials+and+Processes&sig=3FfkDIRvz8MSinhegznHIKn4AvM.
^ MS Sharon Ross , Elise Kinkead (2004). Decorative Painting & Faux Finishes. Creative Homeowner. ISBN 1580111793. books?id=DPJUWRydR9kC&dq=red+yellow+blue+paint-mixing++subtractive&as_brr=3.
^ Swirnoff, Lois (2003). Dimensional Color. W. W. Norton & Company. ISBN 0393731022. books?id=sG5MqtZuFF0C&dq=%22psychological+primaries%22+blue+-green.
^ Bruce MacEvoy. “Do ‘Primary’ Colors Exist?” (Material Trichromacy section). Handprint. Accessed 10 August 2007.
^ “Development of the Idea of Simple Colors in the 16th and Early 17th Centuries”. Color Research and Application. Volume 32, Number 2, April 2007.
^ Bruce MacEvoy. “Secondary Palette.” Handprint. Accessed 14 August 2007. For general discussion see Bruce MacEvoy. “Mixing With a Color Wheel” (Saturation Costs section). Handprint. Accessed 14 August 2007.
^ Cheap Brochure Printing - Process Blue / Process Red / Process Yellow / Process Black
^ Ervin Sidney Ferry (1921). General Physics and Its Application to Industry and Everyday Life. John Wiley & Sons. books?id=3rYXAAAAIAAJ&pg=PA621&dq=date:0-1923+additive+color+mixing+primary&as_brr=1.
^ Frank S. Henry (1917). Printing for School and Shop: A Textbook for Printers' Apprentices, Continuation Classes, and for General use in Schools. John Wiley & Sons. books?id=UAAvAAAAMAAJ&pg=PA292&dq=black+date:0-1923+key-plate+printing+color.
^ See the google image results for “cmyk gamut” for examples.

不知这个可不可以当做论文

关于密码学与密匙管理的信息安全技术论文，3000字。不要地址，要直接的

　　信息安全的密码学与密匙管理

　　一 摘要：
　　密码系统的两个基本要素是加密算法和密钥管理。加密算法是一些公式和法则，它规定了明文和密文之间的变换方法。由于密码系统的反复使用，仅靠加密算法已难以保证信息的安全了。事实上，加密信息的安全可靠依赖于密钥系统，密钥是控制加密算法和解密算法的关键信息，它的产生、传输、存储等工作是十分重要的。
　　二 关键词：密码学 安全 网络 密匙 管理
　　三 正文：
　　密码学是研究编制密码和破译密码的技术科学。研究密码变化的客观规律，应用于编制密码以保守通信秘密的，称为编码学；应用于破译密码以获取通信情报的，称为破译学，总称密码学。
　　密码是通信双方按约定的法则进行信息特殊变换的一种重要保密手段。依照这些法则，变明文为密文，称为加密变换；变密文为明文，称为脱密变换。密码在早期仅对文字或数码进行加、脱密变换，随着通信技术的发展，对语音、图像、数据等都可实施加、脱密变换。
　　密码学是在编码与破译的斗争实践中逐步发展起来的，并随着先进科学技术的应用，已成为一门综合性的尖端技术科学。它与语言学、数学、电子学、声学、信息论、计算机科学等有着广泛而密切的联系。它的现实研究成果，特别是各国政府现用的密码编制及破译手段都具有高度的机密性。
　　密码学包括密码编码学和密码分析学。密码体制设计是密码编码学的主要内容，密码体制的破译是密码分析学的主要内容，密码编码技术和密码分析技术是相互依相互支持、密不可分的两个方面。密码体制有对称密钥密码体制和非对称密钥密码体制。对称密钥密码体制要求加密解密双方拥有相同的密钥。而非对称密钥密码体制是加密解密双方拥有不相同的密钥，在不知道陷门信息的情况下，加密密钥和解密密钥是不能相互算出的。
　　对称密钥密码体制中,加密运算与解密运算使用同样的密钥。这种体制所使用的加密算法比较简单，而且高效快速、密钥简短、破译困难，但是存在着密钥传送和保管的问题。例如：甲方与乙方通讯，用同一个密钥加密与解密。首先，将密钥分发出去是一个难题，在不安全的网络上分发密钥显然是不合适的；另外，如果甲方和乙方之间任何一人将密钥泄露，那么大家都要重新启用新的密钥。通常,使用的加密算法 比较简便高效,密钥简短,破译极其困难。但是,在公开的计算机网络上安全地传送和保管密钥是一个严峻的问题。1976年,Diffie和Hellman为解决密钥管理问题,在他们的奠基性的工作"密码学的新方向"一文中,提出一种密钥交换协议,允许在不安全的媒体上通讯双方 交换信息,安全地达成一致的密钥,它是基于离散指数加密算法的新方案:交易双方仍然需要协商密钥，但离散指数算法的妙处在于:双方可以公开提交某些用于运算的数据，而密钥却在各自计算机上产生，并不在网上传递。在此新思想的基础上,很快出现了"不对称密钥密码体 制",即"公开密钥密码体制",其中加密密钥不同于解密密钥,加密密钥公之于众,谁都可以用,解密密钥只有解密人自己知道,分别称为"公开密钥"和"秘密密钥", 由于公开密钥算法不需要联机密钥服务器，密钥分配协议简单，所以极大地简化了密钥管理。除加密功能外，公钥系统还可以提供数字签名。目前，公开密钥加密算法主要有RSA、Fertezza、EIGama等。我们说区分古典密码和现代密码的标志，也就是从76年开始，迪非，赫尔曼发表了一篇叫做《密码学的新方向》的文章，这篇文章是划时代的；同时1977年美国的数据加密标准（DES）公布，这两件事情导致密码学空前研究。以前都认为密码是政府、军事、外交、安全等部门专用，从这时候起，人们看到密码已由公用到民用研究，这种转变也导致了密码学的空前发展。迄今为止的所有公钥密码体系中，RSA系统是最著名、使用最广泛的一种。RSA公开密钥密码系统是由、和n三位教授于1977年提出的，RSA的取名就是来自于这三位发明者姓氏的第一个字母。RSA算法研制的最初目标是解决利用公开信道传输分发 DES 算法的秘密密钥的难题。而实际结果不但很好地解决了这个难题，还可利用 RSA 来完成对电文的数字签名，以防止对电文的否认与抵赖，同时还可以利用数字签名较容易地发现攻击者对电文的非法篡改，从而保护数据信息的完整性。
　　在网上看到这样一个例子，有一个人从E-mail信箱到用户Administrator，统一都使用了一个8位密码。他想:8位密码，怎么可能说破就破，固若金汤。所以从来不改。用了几年，没有任何问题，洋洋自得，自以为安全性一流。恰恰在他最得意的时候，该抽他嘴巴的人就出现了。他的一个同事竟然用最低级也是最有效的穷举法吧他的8位密码给破了。还好都比较熟，否则公司数据丢失，他就要卷着被子回家了。事后他问同事，怎么破解的他的密码，答曰:只因为每次看他敲密码时手的动作完全相同，于是便知道他的密码都是一样的，而且从不改变。这件事情被他引以为戒，以后密码分开设置，采用10位密码，并且半年一更换。我从中得出的教训是，密码安全要放在网络安全的第一位。因为密码就是钥匙，如果别人有了你家的钥匙，就可以堂而皇之的进你家偷东西，并且左邻右舍不会怀疑什么。我的建议，对于重要用户，密码要求最少要8位，并且应该有英文字母大小写以及数字和其他符号。千万不要嫌麻烦，密码被破后更麻烦。
　　密码设的越难以穷举，并不是带来更加良好的安全性。相反带来的是更加难以记忆，甚至在最初更改的几天因为输人缓慢而被别人记住，或者自己忘记。这都是非常糟糕的，但是密码难于穷举是保证安全性的前提。矛盾着的双方时可以互相转化的，所以如何使系统密码既难以穷举又容易记忆呢，这就是门科学了。当然，如果能做到以下几点，密码的安全还是有保障的。
　　1、采用10位以上密码。
　　对于一般情况下，8位密码是足够了，如一般的网络社区的密码、E-mail的密码。但是对于系统管理的密码，尤其是超级用户的密码最好要在10位以上，12位最佳。首先，8位密码居多，一般穷举工作的起始字典都使用6位字典或8位字典，10位或12位的字典不予考虑。其次，一个全码8位字典需要占去4G左右空间，10位或12位的全码字典更是天文数字，要是用一般台式机破解可能要到下个千年了，运用中型机破解还有有点希望的。再次，哪怕是一个12个字母的英文单词，也足以让黑客望而却步。
　　2、使用不规则密码。
　　对于有规律的密码，如:alb2c3d4e5f6，尽管是12位的，但是也是非常好破解的。因为现在这种密码很流行，字典更是多的满天飞，使用这种密码等于自杀。
　　3、不要选取显而易见的信息作为口令。
　　单词、生日、纪念日、名字都不要作为密码的内容。以上就是密码设置的基本注意事项。密码设置好了，并不代表万事大吉，密码的正确使用和保存才是关键。要熟练输入密码，保证密码输人的速度要快。输人的很慢等于给别人看，还是熟练点好。不要将密码写下来。密码应当记在脑子里，千万别写出来。不要将密码存人计算机的文件中。不要让别人知道。不要在不同系统上使用同一密码。在输人密码时最好保证没有任何人和监视系统的窥视。定期改变密码，最少半年一次。这点尤为重要，是密码安全问题的关键。永远不要对自己的密码过于自信，也许无意中就泄漏了密码。定期改变密码，会使密码被破解的可能性降到很低的程度。4、多方密钥协商问题
　　当前已有的密钥协商协议包括双方密钥协商协议、双方非交互式的静态密钥协商协议、双方一轮密钥协商协议、双方可验证身份的密钥协商协议以及三方相对应类型的协议。如何设计多方密钥协商协议？存在多元线性函数(双线性对的推广)吗？如果存在，我们能够构造基于多元线性函数的一轮多方密钥协商协议。而且，这种函数如果存在的话，一定会有更多的密码学应用。然而，直到现在，在密码学中，这个问题还远远没有得到解决。

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