Cryptography -- 密码学

2024-09-05 03:24:49

Introduction to Cryptography

Cryptography enables you to store sensitive information or transmit it across insecure networks (like the Internet) so that it cannot be read by anyone except the intended recipient.
Cryptanalysis is the science of analyzing and breaking secure communication.

Encryption and Decryption

PlainText or ClearText
- Data that can be read without any special measures.
Encryption
- "Method of disguising plaintext in such a way as tohide its content"
CipherText
- "Encrypting plaintext result in unreadable gibberish"

Requirement of computational secure encryption scheme (加密安全的需求)

Cost of breaking the cipher exceeds the value of the encrypted information
Time required to break the cipher exceeds the useful lifetime of the information

Symmetric-Key Encryption

Single-key, secret-key or conventional encryption
One key is used both for encryption and decryption.

Pros

Much faster than asymmetric systems
Hard to break if using a large key size

　　Cons

Key distribution 密钥分配
- It requires a secure mechanism to deliver keys properly
Scalability 可扩展性
- Each pair of users needs a unique pair of keys, so the number of keys grow exponentially
Limited security 有限的安全性
- It can provide confidentiality, but not authenticity or non-repudiation 它可以提供机密性，但不提供真实性或不可否认性

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