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密码学-学习笔记2-Block Ciphers
source link: https://iamywang.github.io/2020/study-block-cipher/
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密码学-学习笔记2-Block Ciphers
0x01 分组加密示意图
密钥扩展出n个轮密钥,以及使用轮密钥加密n轮:
0x02 PRP和PRF
PRP例子(PRP都是PRF):
- AES:K × X -> X(K = X = {0,1}^128) |
一些要考虑的问题:
安全PRF:... |
PRF ⇒ PRG:
G(k) = F(k,0) || F(k,1) || ... || F(k,t-1) |
也可以从PRG构造PRF:
Luby-Rackoff定理、GGM PRF |
0x03 DES
Feistel Network:
S盒:Si: {0,1}^6 -> {0,1}^4
0x04 攻击方式
穷举攻击 - Exhaustive Search Attack:
DES:2^56 |
中间相遇攻击 - Meet In The Middle Attack:
以空间换取时间的一种攻击方法。 |
其他攻击方式:
侧信道攻击:测量time和power。 |
0x05 AES
Subs‐Perm Network:
AES-128 示意图:
攻击方式:
Best Key Recover Attack:比穷举好四倍 |
0x06 操作模式:one-time key
- Adv能看到密文(使用一次性密码) |
0x07 安全性:many-time key
- Adv可以看到多个同一个密钥加密的密文。 |
0x08 操作模式:many-time key(CBC)
CBC加密:
CBC解密:
0x09 操作模式:many-time key(CTR)
CTR模式示意图:
CBC和CTR对比:
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