1. Hash algorithm and digital digest
1. Hash definition
Hash algorithm, which can map binary plaintext strings of arbitrary length into shorter (usually fixed-length) binary strings (Hash values)
Features: forward fast, reverse difficult, input sensitive, conflict avoidance
2. Common Algorithms
MD5 and SHA family of algorithms. SHA (Secure Hash Algorithm) is not an algorithm, but a family of Hash functions.
MD5 and SHA-1 have been cracked, at least SHA-256 or a more secure algorithm is recommended
3. Performance
Hash is generally computationally sensitive. The higher the CPU frequency, the faster the algorithm.
The Scrypt algorithm is not computationally sensitive, requires a lot of memory resources, and cannot improve Hash performance by increasing the CPU.
4. Digital Summary
Digital digest is to perform Hash operation on digital content to obtain a unique digest value to refer to the original complete digital content. Digest of numbers is one of the most important uses of the Hash algorithm. Using the anti-collision feature of the Hash function, the digital digest can solve the problem of ensuring that the content has not been tampered with.
5. Hash attack and protection
The Hash algorithm is not an encryption algorithm and cannot be used to protect information. But it is often used for the preservation of passwords.
2. Encryption and decryption algorithm
1. Basic composition of encryption and decryption system
Generally include: encryption and decryption algorithm, encryption key, decryption key.
2. Symmetric encryption algorithm
The keys for the encryption and decryption process are the same.
There are two types of ciphers: block ciphers and sequence ciphers.
3. Asymmetric encryption algorithm
Encryption and decryption keys are different and are called public and private keys, respectively.
4. Chosen-plaintext attack
Since the public key is publicly available, anyone can give the plaintext and obtain the corresponding ciphertext, which brings the risk of chosen-plaintext attack.
5. Hybrid encryption mechanism
Combines the advantages of encryption and asymmetric encryption.
6. Discrete logarithms and Diffie–Hellman key exchange protocol
3. Message Authentication Code and Digital Signature
1. Message Authentication Code
2. Digital Signature
3. Security
4. Digital certificate
5. PKI system
Six, Merkle tree structure
7. Bloom filter
8. Homomorphic encryption
9. Other issues
In other words, this chapter is completely overwhelmed, and I basically don't understand~~~