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用Java语言编写的数据传输小软件 基于P2P传输模式 可以多线程传送 类似于QQ 速度和QQ差不多

Why do we need a data encryption standard, since proprietary encipherment 
systems are available from many manufacturers? Users wishing to protect 
communication on a line need only purchase a pair of matching encipherment 
devices, and they are ready to communicate securely.
When protected communication is required between users who belong to 
different organisations, this may not be so easy to arrange. The organisations 
may have chosen encipherment devices from different manufacturers,
in which case the devices are likely to be totally incompatible and unable to 
communicate either securely or otherwise. Furthermore, encipherment must 
often be introduced in the context of standard communication protocols; this 
may place new restrictions on the means of encipherment.