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Mobile Payments

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by

Dapeng Zhang

on 11 July 2015

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Transcript of Mobile Payments



密码学和网络安全

Alan Turing

阿兰 图灵

1912-1954
计算机之父
图灵测验提出者
破译德军 Enigma 密码系统
提前两年结束二战
著名同性恋者
图灵奖
密文:pldr
凯撒移位密码
解密:频率分析
解密:密文攻击
2. 攻击者只知道是简单替换方式加密
1. 攻击者知道使用了凯撒密码加密
穷举替换-最多需要25次
单码替换
古典加密方法
多码替换
THERE ARETW OWAYS OFCON STRUC TINGA SOFTW AREDE SIGNO NEWAY
SYSTE MSYST EMSYS TEMSY STEMS YSTEM SYSTE MSYST EMSYS TEMSY
LFWKI MJCLP SISWK HJOGL KMVGU RAGKM KMXMA MJCVX WUYLG GIISW
ISTOM AKEIT SOSIM PLETH ATTHE REARE OBVIO USLYN ODEFI CIENC
STEMS YSTEM SYSTE MSYST EMSYS TEMSY STEMS YSTEM SYSTE MSYST
ALXAE YCXMF KMKBQ BDCLA EFLFW KIMJC GUZUG SKECZ GBWYM OACFV

IESAN DTHEO THERW AYIST OMAKE ITSOC OMPLI CATED THATT HEREA
EMSYS TEMSY STEMS YSTEM SYSTE MSYST EMSYS TEMSY STEMS YSTEM
MQKYF WXTWM LAIDO YQBWF GKSDI ULQGV SYHJA VEFWB LAEFL FWKIM

RENOO BVIOU SDEFI CIENC IESTH EFIRS TMETH ODISF ARMOR EDIFF
SYSTE MSYST EMSYS TEMSY STEMS YSTEM SYSTE MSYST EMSYS TEMSY
JCFHS NNGGN WPWDA VMQFA AXWFZ CXBVE LKWML AVGKY EDEMJ XHUXD

ICULT
STEMS
AVYXL
http://www.cs.mtu.edu/~shene/NSF-4/Tutorial/VIG/Vig-Kasiski.html
Enigma
古典加密方法:

f (明文) = 密文

解密:

f^(-1) (密文) = 明文

关键问题: f 的寻找
现代加密方法:

f (明文,秘钥) = 密文

解密:

f^(-1) (密文,秘钥)= 明文

关键问题:秘钥的安全性
加解密使用同一秘钥:对称加密

常用f : AES (高级加密标准)
对硬件要求低(Wlan, SSL ...)


加解密使用不同秘钥:非对称加密

f (明文,公钥) = 密文

f^(-1) (密文,私钥) = 明文



RSA:基于素数分解

17*13=221

椭圆曲线
单向暗门函数

f 容易计算 , f^(-1) 困难

常用f:RSA, 椭圆曲线加密


安全性只依赖于密码强度

警惕社会工程学

定期更换密码
Full transcript