Diffie-Hellman Diffie-Hellman is a public key distribution scheme First public-key type scheme, proposed in 1976. W Diffie, M E Hellman, \New directions in Cryptography\, IEEE Trans. Information

A. J. Menezes, P. C. van Oorschot and S. A. Vanstone. Handbook of Applied Cryptography, CRC Press, 1997. Bruce Schneier. Applied Cryptography, Second Edition: Protocols, Algorthms, and Source Code in C (cloth) John Wiley & Sons, Inc.) 1996 Douglas R. Stinson, Cryptography (Theory and Practice), CRC Press 1995 Resources

Definition: Group A set G of elements and operator @ form a group if: for all x,y in G, x @ y is also in G (inclusion) there is an identity element e such that for all x in G, e@x = x for all x in G, there is an inverse element x

Digital Signatures and Message Authentication Code (MAC) overview Suppose Alice and Bob share a secret key k which determines hash function hk Alice sends (x, y) to Bob where y = hk

Modular arithmetic – Used to define a finite field – a = b mod n means that if a and b are divided by n they produce the same remainder – a*b mod n can result in 0 even if a and b are not 0

Originally designed to be efficient in hardware . A LOT of money has been invested in hardware. although DES standard is public there was considerable controversy over design – in choice of 56-bit key (vs Lucifer 128-bit) – and because design criteria were classified

Cryptographic protocol – Distributed algorithm – Based on cryptographic building blocks – To achieve a security related goal Examples: – Entity Authentication – Key Establishment:Key Distribution(Key enveloping, Key transport), Key agreement – Electronic Payment

MPEG 是目前最常用的一项音频 / 视频压缩技术，它实际 上并不是一个单一的标准，而是包括了适合于各种不同 应用的一系列标准，但这些标准是以一些共同理论为基 础的。MPEG是活动图象专家组的缩写词，该专家组是联 合技术委员会(Joint Technical Committee，JTC1)的一部分， JTC1是由ISO(国际标准化组织)和IEC(国际电工委员会)建 立的。JTC1负责信息技术，在JTC1 中，下设有负责“音 频、图象编码以及多媒体和超媒体信息”的子组SG29

• 计算机网络体系结构 • 局域网技术 • TCP/IP协议 • 网络互联技术 • WWW技术

11 月 13 日，江苏省苏州市金阊区人民法院宣判一起由于精神病人跳楼身亡 引发的人身损害赔偿纠纷案。虽然精神病院与精神病人的监护人协议约定医院对 精神病人自杀、自伤等意外情况不负责任，但法院最终还是判决医院承担 20% 的赔偿责任