对欲访问特定信息的发起者的身份或者对传送的报文完整性进行合法性审查或核实的行为称为(50)。在日常生活中，我们可以用手写签名来防止否认的发生。在计算机通信中，要解决这类问题，可采用的方法是(51)。关于客户/服务器应用模式，说法正确的是(52)。在理论上，加密能够在OSI模型的任何一层上实现，但是实际上最适合于实现加密的有三层，它们是(53)。网络防火墙的安装位置应该在(54)。

(82)

(81)

(79)

(80)

(71) In the strength of the carrier signal is varied to represent binary 1 or 0.

  (72) is a system that can map a name to an address and conversely an address to an name.

  (73) is a three-way handshaking authentication protocol that it's packets are encapsulated in the point-to-point protocol

  (74) is an approach that enables an ATM Switch to behave like a LAN switch.

  (75) is an guided media which is made of glass or plastic and transmits signals in the form. of light.

(76)

(77)

(74)

(75)

(72)