完成集中式对称密钥的分配工作

说明：作为通讯的双方A和B，都已经分别和KDC拥有会话密钥Ka和Kb，但A、B之间事先没有保密通道，需要依赖KDC为它们的会话分配临时密钥Ks。在完成会话密钥Ks的分配后，A利用Ks对特定文件（test-1.txt）进行加密，并发送给B；B利用Ks对密文进行解密，并对比解密后的明文信息同原来的文件是否一致。

要求：

（1）JAVA语言编程实现，基于DES完成对称密码技术的加/解密（JAVA有库函数支持）；

（2）通信内容为一文本文件（test-1.txt）；

（3）基于网络完成密钥分配工作（作为通信的双方A、B应部署于两台主机上，KDC可以部署在其中一台主机上或第三台主机上）；

（4）所分配的对称密钥皆为一次一密，随机产生；

（5）具体密钥分配过程请以课本中基于KDC的集中式密钥分配方案为参考，完成从步骤1到步骤5的全过程；-Complete centralized allocation symmetric key

Descr iption: As a communication between the parties A and B, respectively, and the KDC already has a session key Ka and Kb, but the A, B no secret passage between the advance, they need to rely on the KDC allocate temporary session key Ks. Upon completion of the session key Ks allocation, A Ks on the use of a specific file (test-1.txt) is encrypted and sent to B　B use Ks decrypt the ciphertext, and compare the decrypted plaintext message with the original files are consistent.

Requirements:

(1) JAVA programming language, based on the DES symmetric cryptographic techniques to complete the encryption/decryption (JAVA library functions are supported)

(2) the content of communications as a text file (test-1.txt)

(3) complete network-based key distribution job (as the communication between the parties A, B should be deployed on both hosts, KDC can be deployed on one host or a third host)

(4) are allocated once a secret symmetric key ra