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Introduction to Modern Cryptography Reading Notes

3 Private-Key Encryption

具体安全和渐进安全

安全有两种定义,具体的(concrete)渐进的(asymasymptotic)。简单地说,具体安全依靠具体的数值,而渐进安全依靠关于 n 的函数。

对于具体安全的定义

A scheme is (t,ε)-secure if any adversary running for time at most t succeeds in breaking the scheme with probability at most ε.

在实际运用密码系统时往往需要一个具体的安全保障。

我们将 efficient adversaries 视为多项式时间随机算法(randomized algorithms running in time polynomial in n);将 small probabilities of success 视为不大于某一多项式的倒数(success probabilities smaller than any inverse polynomial in n),这样的概率成为可忽略的(negligible)

PPT 表示 probabilistic polynomial-time

渐进安全进行定义:

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