查询词典 substitution cipher

The symmetric algorithm is a traditional algorithm, it is easy and efficient, and so it is still being popular used. The stream cIPher and the block cIPher are two part of the symmetric algorithm. The symmetric algorithm uses the key to control the key stream generator, and then the generator produces a random stream. We can get the cIPher by xor the message and the random stream by bit. In the field of communication and code, the stream cIPher has always been the key cIPher of the military affairs and foreign affairs.

对称密码体制分为序列密码和分组密码两类，序列密码以密钥控制密钥流发生器，产生一随机序列，用这个随机序列和明文信息逐位异或，就得到密文，其加密单元为比特。

It must improve the commonly symmetrical key block cipher arithmetic for ensuring that the data length will not be increased after encryption: using forward shift bits mode in Triple DES with Two Keys; using cipher text stealing mode in RC5 with Cipher Block Chaining.

为保证加密后数据长度不变，应对常用的对称密钥分组密码算法以改进：双密钥三重DES加密采用向前挪位法，RC5密码分组链接加密采用密文窃取方式。

For example, if the two methods used are the Playfair cipher and simple columnar transposition, if transposition is used first, the Playfair cipher can still be attacked, because it takes each input letter to a limited number of substitutes; if the Playfair cipher is used first, multiple anagramming, although now much more difficult, is still possible because a text enciphered by Playfair still has digraph frequencies marked well enough to allow a correct match to be detected.

例如，如果这两种方法用的是playfair密码和简单的柱状移位，如果移位是用第一， playfair密码仍然可以被攻击，因为它需要每个输入信有限数量的代用品；如果playfair密码是用来首先，多重anagramming ，虽然现在困难得多，仍然有可能因为一个文本加密由playfair仍然有向图的频率明显做得不够好，让一个正确的匹配，以进行检测。

In our research on study chemical reaction of active methylene compounds and brom-acetophenone. Because of brom-acetophenone is compound that contain carbonyl and halogen ,which will take place electrophilic substitution and nucleophilic addition. When active methylene compounds are ethyl acetoacetate and β-diketone, controlling reaction condition, we have found that mono-substitution's production and di-substitution's. production is isolated; active methylene compounds are acetoacetanilide and acetoacetanilide derivate, pyrrolidin-2-one derivants were obtained by substitution and close-ring reaction .but there is no report about it.

本文是让活泼亚甲基类化合物与溴代苯乙酮发生化学反应，由于溴代苯乙酮是含有羰基的卤代烃结构，它可以发生亲电取代和亲核加成反应，当活泼亚甲基类化合物为乙酰乙酸乙酯和β-二酮时，控制反应条件可以发生单取代和双取代两种产物；当活泼亚甲基类化合物为乙酰乙酰芳胺类化合物来反应时，溴代苯乙酮中的羰基与氨基会发生分子内的关环反应生成吡咯烷-2-酮衍生物，这在以前的研究中是没有发现的。

The effects of the mechanism on both the efficiency of options investment and on the substitution of the incentive mechanism are analyzed. These substitution effects involve two aspects: the complete substitution to efficiency of investment exercising and the partial substitution to information rents.

重点分析了审核机制对投资期权执行效率的影响以及对激励机制的替代作用，这种替代作用表现为在投资执行效率方面的完全替代和在信息租金方面的部分替代。

In cryptography,a cipher produced by a composition of a number of substitution and transposition cipher s.

密码学中，由替代密码和置换密码结合使用而构成的一种密码。

The block cipher with a substitution permutation network is the best known and widely used block cipher system.

包含代替置换网络的分组密码是一种广泛使用的分组密码系统。

One of the simplest examples of a substitution cipher is the Caesar cipher, which is said to have been used by Julius Caesar to communicate with his army.

对一替代密码的一个最简单的例子是凯撒密码，据说是被凯撒用于与他的军队。

In a typical example emphasized index of coincidence in Kerckhoff assumption to cryptanalyze the polyalphabetic substitution cipher, the Vigenère cipher for exemple.

针对一个典型实例重点讲解重合指数法在Kerckhoff假设下破解多表代换（以Vigenère密码为例）方面的应用。

We provide a substitution box, exponential permutation which has much measurable security, and give a enumerating result and a fast algorithm of calculating such permutation. An almost perfect nonlinear exponential permutation with high algebric degree is proposed. with some discussion on how to select the parameters of such permutation. The experimental result shows us a conjecture that there exists no such permutation over even dimensional space. As a way of generating substitution boxes, we briefly point out the cryptographic weakness of the exponential functions derived from such permutation. We also present two new cryptographic indexes, fixed point and cyclic structure, on which we investigate the performance of such permutation. Finally, we give a viewpoint about the application of correlation immune functions in designing substitution boxes.

提供了一种可度量安全强度的代换盒－幂置换；详细阐述了幂置换的实现和计数问题；给出了一种计算幂置换的快速算法；从几乎完善非线性幂置换角度讨论了幂置换参数的选取，并提出了一种高次几乎完善非线性置换；通过试验给出了关于偶数维空间上几乎完善非线性幂置换的一个猜想；简要给出了由幂置换派生出的幂函数的密码局限性；针对幂置换，提出了两个密码安全指标：不动点和循环结构；证明了幂置换在这两个指标下的密码性能；简要讨论了相关免疫函数与代换盒设计的关系。

If you were not , and OS X just booted normally, have no fear.

如果你没有，和OS X刚刚启动通常，没有恐惧。

I only want to preserve our all .

我只想保存好我们的一切