Public key encryption, also known as asymmetric key encryption (public key encrypTIon), belongs to the second class of network security under communication technology, and refers to a pair of unique keys (ie public key and private secret). The encryption method consisting of the key). It solves the problem of key release and management and is the core of current commercial passwords. In the public key cryptosystem, what is not disclosed is the private key, and the public key is disclosed.
RSA, ElGamal, backpack algorithm, Rabin (Rabin's encryption method can be said to be a special case of RSA method), Diffie-Hellman (DH) key exchange protocol public key encryption algorithm, EllipTIc Curve Cryptography (ECC, elliptic curve encryption algorithm) . The most widely used RSA algorithm (acronym by the inventors Rivest, Shmir, and Adleman) is a well-known public key encryption algorithm, and ElGamal is another commonly used asymmetric encryption algorithm.
asymmetricIt refers to a pair of encryption key and decryption key. These two keys are mathematically related. The information obtained by encrypting with a user key can only be decrypted by using the decryption key of the user. If you know one of them, you can't figure out another one. Therefore, if one of a pair of keys is disclosed, it does not endanger the secret nature of the other. The public key is called the public key; the undisclosed key is the private key.
If the encryption key is public, this is used by the client to upload encrypted data to the private key owner, which is referred to as public key encryption (narrow sense). For example, encrypted data of an account operation issued by a customer of an online bank to a bank website.
If the decryption key is public, the information encrypted with the private key can be decrypted with the public key, and the client can verify that the data or file published by the party holding the private key is complete and accurate, and the recipient can know the information. It does come from someone who owns a private key. This is called a digital signature. The public key is in the form of a digital certificate. For example, an installer downloaded from the Internet generally has a digital signature of the program creator, which can prove that the program was indeed published by the author (company) and not forged by a third party and has not been tampered with (identification/verification). .
Symmetric key cryptosystem
The symmetric key cryptosystem, that is, the encryption key and the decryption key are the same cryptosystem.
The data encryption standard DES belongs to the symmetric key cryptosystem. It was developed by IBM and became a federal information standard in the United States in 1977, which has attracted great attention internationally. ISO used DES as a data encryption standard.
DES is a block cipher. The entire plaintext is grouped before encryption. Each group has 64 bits of binary data. Each 64-bit binary data is then encrypted to produce a set of 64-bit ciphertext data.
Finally, the ciphertexts of each group are concatenated to obtain the entire ciphertext.
Common encryption algorithms can be divided into three categories, symmetric encryption algorithms, asymmetric encryption algorithms and Hash algorithms.
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