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密码学基本构件
网络安全依赖于几种密码学原语：以密钥为参数的密码，使算法可以公开而只有密钥保密；秘密密钥分组密码（如 DES 及其后继算法）能快速混淆固定大小的分组；公钥密码（如 RSA）将密钥拆分为任何人都可用的公钥和只有所有者持有的私钥，根据使用方向的不同可提供保密性或认证，但速度太慢，不适合处理大量数据；还有基于抗碰撞哈希的认证器、以共享秘密为密钥的消息认证码，以及数字签名——用私钥加密的哈希值，其中只有数字签名能提供不可否认性，因为只有所有者才能生成它们。
1. Keys, Not Algorithms
Keys, Not Algorithms
2. From Blocks to Messages
From Blocks to Messages
3. Two Halves of One Key
Two Halves of One Key
4. Proving Integrity
Proving Integrity
5. The public algorithm
Why are cipher algorithms published rather than kept secret?
6. Repairing DES
Why does 3DES encrypt with key1, decrypt with key2, and encrypt with key3 rather than encrypting three times?
7. Two directions, two properties
What does encrypting with a private key achieve, given that anyone can decrypt with the public key?
8. The birthday shortcut
Why does a 128-bit digest offer only about 64 bits of collision resistance?
9. The third party
Why can a digital signature convince a judge while a MAC cannot?
10. The hybrid pattern
How do real systems combine public-key and secret-key ciphers?
11. The secret half
In a public-key cipher, which half of the key pair never leaves its owner?
12. The fixed-size fingerprint
What is the fixed-size output of a cryptographic hash function called?
13. The keyed digest
What do you get when a shared secret key is folded into a message digest so only key holders can produce it?
14. The undeniable proof
What authenticator is made by encrypting a digest with the sender's private key, providing nonrepudiation?