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计算机网中采用加密技术,保密性即密码强度以及密钥管理都是重要问题。若将有代表性的加密方式——点对点加密方式(简称E方式)和链路加密方式(简称L加密方式)——加以比较,L方式虽然比E方式应发送的密钥数量少,但在保密性方面存在某些弱点。其中之一是:由于各个节点出现明文,如果某个节点不可靠,保密性就没有保证。假如输入至各个节点的密文不恢复成明文而直接变换成密文输出就可以克服这一弱点。但是,适合这样一种链路加密方式——直接变换型链路加密方式(简称D方式)——的密码体制必须具有某种条件。本论文将给出这个条件,并且说明一次一密密码体制、幂方密码体制和PSA公开密钥密码体制都适用于D加密方式。本文还将对采用通用密码体制和公开密钥密码体制的E、L及D三种加密方式的保密性和应发送的密钥数作进一步的比较,并可得出如下结论:(i)保密性按L、D、E的顺序递增;(ii)应发送的密钥数,在采用通用密码体制时按E、D、L的顺序、采用公开密钥密码体制时按E、L、D的顺序递减。
Computer network encryption technology, the confidentiality of the password strength and key management are important issues. If we compare the representative encryption methods-point-to-point encryption (referred to as E) and link encryption (L-encrypted), the number of keys in L is less than that of E, There are some weaknesses in confidentiality. One of them is that because of the plaintext in each node, if a node is unreliable, there is no guarantee of confidentiality. This weakness can be overcome if the ciphertext input to each node is not restored to plaintext but directly converted to ciphertext output. However, a cryptosystem that suits such a link encryption scheme, the Direct Conversion Link Encryption Scheme (referred to as D scheme), must have certain conditions. This paper will give this condition and show that a one-time password system, power-side password system and PSA public-key cryptosystem are all suitable for D-encryption. This article will further compare the confidentiality of the three encryption methods E, L and D using the common cryptosystem with the public key cryptosystem and the number of keys that should be sent, and draw the following conclusions: (i) Confidentiality (Ii) The number of keys that should be sent, in the order of E, D, and L when using a common cryptosystem, in the order of E, L, D when using the public key cryptosystem Decreasing order.