密文

If the same block is encrypted twice with the same key, the resulting ciphertext blocks are the same.

如果相同的块加密两次使用相同的密钥，由此产生的密文块是相同的。

The following is a notation for relating plaintext, ciphertext, and keys.

下面是有关明文、密文和密钥关系的表示法。

Algorithm is general information or information can be understood with a string of numbers combine to produce the ciphertext can not understand the steps, key is used to encode the data and a decryption algorithm.

算法是将普通的信息或者可以理解的信息与一串数字结合，产生不可理解的密文的步骤，密钥是用来对数据进行编码和解密的一种算法。

Its encryption method is to express the letter in accordance with the order given in a matrix, and then use the key provided in accordance with the order re-arrangement of the letters in the matrix to form a ciphertext.

它的加密方法是将明文中的字母按照给定的顺序安排在一个矩阵中，然后用根据密钥提供的顺序重新组合矩阵中的字母，形成密文。

If we receive a ciphertext and the MAC over the ciphertext is valid, we presume with very high probability that the message came from our peer and has not been tampered.

如果我们收到密文，并在密陆委会是有效的，我们具有非常高的概率推定该消息来自我们的同行，也没有被篡改。

In DAS model,one important problem faced is how to improve the query efficiency in the encryption database,and cryptograph index technology is one of the methods to improve cryptograph query efficiency in database.

DAS模型下，如何提高密文数据库的查询效率是当前面临的一个主要问题，而密文索引技术是提高数据库中密文查询效率的手段之一。

The cryptography technology based on the private or public key can be used to control the data access and change the straightforward information into the baffling cryptograph information.

基于私有或公共密钥的加密技术可以用来控制数据访问，它将明文消息变换成旁人无法理解的密文消息。

The main content of this thesis includes six parts. First of all, it is a comprehensive systematic introduction about RSA algorithm including the present application situation and principle of RSA algorithm----producing big prime numbers and secret keys, the encryption arithmetic for information and the decryption for secret information, which establish the theory foundation for achieving concrete; secondly, it introduces some basic conception of RSA digital signature and theory of digital signature realizing process; thirdly, it introduces the basic principle of MD5 algorithm; fourthly, it states design and realization of RSA digital signature in detail. The main modules includes producing RSA secret keys, implementation of RSA encryption algorithm and decryption algorithm, producing message digest and realizing digital signature and verification by RSA; the fifth, it carries on testing entirely, analyzing and improving for this system;The sixth, it analyses the security of RSA digital signature and points out the development direction of RSA digital signature.

本文主要研究的内容包括：第一，对RSA算法进行了全面系统的介绍，包括RSA算法的应用现状和原理—大素数的产生、密钥对的产生、对明文的加密运算和密文的解密运算，为具体实现打下了理论基础；第二，介绍了RSA数字签名的一些基本概念和数字签名的理论实现过程；第三，对MD5算法基本原理的介绍；第四，详述了RSA数字签名的设计与实现，主要实现的模块包括RSA密钥的产生，RSA加密算法和解密算法的实现，消息摘要MD的生成以及利用RSA算法实现数字签名和签名的验证；第五，对该系统进行了整体的测试和分析改进；第六，分析了RSA数字签名的安全性，指出了RSA数字签名的发展方向。

Computation of modular exponentiation is very low because of big plain-text group and cipher-text group,so this algorithm is of great significance to design fast algorithm of RSA and select public-key and private-key of RSA.

RSA算法中明文分组和密文分组都较大，方幂模运算消耗大量的运算时间。因此，简化方幂模计算减少计算次数对设计RSA快速算法和选择密钥具有重要的指导意义。

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。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。