IPSec简介

imouse posted @ 2012年10月11日 02:39 in Linux with tags IPSec ESP AH , 1412 阅读

介绍


    IPsec是一种虚拟网络的应用,可以将internet虚成企业网来用,比如,公司在上海和北京都有办公区,两边为了能互相访问方便,一种解决方法是租用一条专用路线,物理上保证带宽和传输安全性,但是这样造价很高,有了VPN可以在inetenet上做一个逻辑层面上的网络,数据在彼此交换都使用AH或ESP方式对IP头部/载荷进行加密认证.这样保证了传输的安全性,但带宽就不好保证了, 总体来说VPN是较好的解决方案,节省成本.

工作模式


    IpSec工作在两种模式下:传输模式, 隧道模式.区别与隧道模式,传输模式对IP头部不再次封装,而隧道模式会根据配置规则把原始数据包封装到一个新的IP数据包中.


加密方式


    IPsec支持AH/ESP两种加密方式.
    严格的来说, AH不是一种加密方式,而是对数据的校验或称数字签名.校验范围如下:

    +------------+-----------+------------+
    | ip header  | AH header | ip payload |
    +------------+-----------+------------+
    | ------- verify scope ---------------|
   
    发送过程中,增加一个AH头部,使用hash算法将IP头部+IP数据区进行校验生成fingerpoint,然后对fingerpoint加密填入AH header中.
这种校验方式可以防止数据传输过程被第三方篡改,但IP数据区的数据还是明文,并没有真正加密.
    ESP则是真正意义上的加密.对数据加密后,数据区就会变成密文,无法直接识别,需要解密之后才能处理.
 

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