Beginner's Guide to Host Computer Development (7) Encryption Algorithm
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foreword
Encryption algorithm is one of the important technologies in the field of information security, which can protect the security of data during transmission, storage and processing.
Learning encryption algorithms can help us better understand and apply other related technologies. For example, digital certificates, digital signatures, security protocols, etc. are closely related to encryption algorithms, and mastering encryption algorithms can help us understand and apply these technologies.
Classification of Encryption Algorithms
According to different dimensions, encryption algorithms can be divided into the following types.
Symmetric encryption algorithm and asymmetric encryption algorithm
Symmetric encryption algorithms use the same key for encryption and decryption, while asymmetric encryption algorithms use public and private keys for encryption and decryption.
- Symmetric encryption algorithm: DES, 3DES, AES, etc.
- Asymmetric encryption algorithms: RSA, DSA, ECC, etc.
Stream ciphers and block ciphers
A stream encryption algorithm divides the input data into a series of continuous streams and encrypts each stream. Block ciphers divide the input data into blocks and encrypt each block.
- Stream encryption algorithms: RC4, Salsa20, ChaCha20, etc.
- Block encryption algorithms: AES, Blowfish, Twofish, etc.
block ciphers and sequence ciphers
A block cipher is a block encryption algorithm that divides the input data into fixed-size blocks and encrypts each block. A sequence cipher is a stream encryption algorithm that takes input data as a continuous stream of bits and encrypts each bit.
- Block ciphers: AES, Blowfish, DES, etc.
- Sequence code: RC4, Salsa20, ChaCha20, etc.
Do you feel that "stream encryption algorithm and block encryption algorithm" are very similar to "block cipher and sequence cipher"?
There is a certain relationship between the block encryption algorithm and the block cipher algorithm, and there is a certain relationship between the stream encryption algorithm and the sequence cipher algorithm. However, they are not completely equivalent concepts, because their division is based on different encryption methods and methods of processing data.
Hash functions and message authentication codes
Hash functions map arbitrary-length input data to fixed-length output data and are commonly used in digital signatures and authentication. Message authentication code uses a key to encrypt input data and generate fixed-length output data, which is often used for data integrity verification and message authentication.
- Hash functions: SHA-1, SHA-2, SHA-3, etc.
- Message authentication code: HMAC, CMAC, Poly1305, etc.
Hash functions and message authentication codes are essentially digest algorithms, but because they are widely used in the field of encryption, they are mentioned again in this chapter. For more information about the summary algorithm, please refer to the previous article "Beginner's Guide to PC Development (6) Summary Algorithm".
Symmetric encryption and asymmetric
In several classifications, symmetric encryption and asymmetric encryption are worth discussing, because they are the two most commonly used types of encryption algorithms and play an important role in practical applications, but their principles and uses are different. different.
Symmetric encryption uses the same key to encrypt and decrypt data. This means that only those who hold the same key can decrypt the data.
Asymmetric encryption uses public and private keys to encrypt and decrypt data. Public keys can be distributed publicly, while private keys are only accessible to the holder. The sender encrypts the data with the receiver's public key, and only the receiver can decrypt the data with its private key.
Symmetric encryption
Symmetric encryption uses the same key to encrypt and decrypt data. It has the following advantages and disadvantages:
advantage
Fast encryption and decryption speed : The encryption and decryption process of the symmetric encryption algorithm is very fast, which is suitable for scenarios where a large amount of data is processed.
Good for encrypting large files : Symmetric encryption algorithms can encrypt large files because encryption and decryption are fast.
Simple algorithm : The implementation of symmetric encryption algorithm is relatively simple and does not require a lot of computing resources.
shortcoming
Difficulty in key management : Symmetric encryption algorithms require a secure shared key between the sender and receiver, and if the key is compromised, the data is at risk.
Less secure : Symmetric encryption algorithms are less secure because the same key is used for encryption and decryption. If the key is compromised, the data cannot be protected.
Not suitable for a distributed environment : Symmetric encryption algorithms are not suitable for use in a distributed environment because the sender and receiver are required to share a key, and the receiver in a distributed environment may be constantly changing.
Symmetric encryption algorithms are suitable for scenarios that require fast encryption and decryption, but key management and security are issues that need to be considered.
Symmetric encryption algorithm usage process
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Key Generation: The encrypting party chooses a key and transmits that key confidentially to the decrypting party.
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Plaintext encryption: The encryptor uses a symmetric encryption algorithm and a key to encrypt plaintext to generate ciphertext.
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Ciphertext transmission: The encrypting party transmits the ciphertext to the decrypting party.
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Ciphertext decryption: The decryption party uses the same symmetric encryption algorithm and key to decrypt the ciphertext and restore the plaintext.
asymmetric encryption
Compared with symmetric encryption, asymmetric encryption has the following advantages and disadvantages:
advantage
The public key of asymmetric encryption can be distributed publicly, while the private key can only be accessed by the holder. Therefore, asymmetric encryption does not require a shared key between the sender and receiver, which makes key management easier.
Asymmetric encryption is more secure, because encryption and decryption use different keys, even if an attacker obtains the public key, he cannot use the public key to decipher the encrypted data.
shortcoming
The disadvantage of the asymmetric encryption algorithm is that the encryption and decryption speed is slow, and it is not suitable for encrypting large files. In addition, verifying identities requires a certain level of complexity, and while it can be used for digital signatures, it requires certain technical knowledge to implement.
Asymmetric encryption algorithms have higher security and easier key management, but factors such as encryption and decryption speed, applicable scenarios, and technical costs need to be weighed to determine whether to use this encryption method.
The process of using asymmetric encryption
The process is as follows:
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First, the recipient generates a pair of public and private keys.
公钥可以公开分发，而私钥只能由接收方持有. -
The sender encrypts the data with the receiver's public key and sends the encrypted data to the receiver.
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The recipient uses its own private key to decrypt the encrypted data to obtain the original data.
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If signature verification is required, the receiver signs the data with its own private key and sends it to the sender.
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After receiving the signature, the sender uses the recipient's public key to verify the signature, thereby confirming the source and integrity of the data.
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