What Is a Cipher Key?
A key is a parameter that is entered in an algorithm that converts plaintext to ciphertext or converts ciphertext to plaintext. Keys are divided into symmetric keys and asymmetric keys.
- There are two types of keys: symmetric keys and asymmetric keys
- Two keys
- According to whether the encryption and decryption keys used by the cryptographic algorithm are the same
- Symmetric key encryption , also known as private key encryption or session key encryption algorithm, means that the sender and receiver of information use the same key to encrypt and decrypt data. Its biggest advantage is its fast encryption / decryption speed, which is suitable for encrypting a large amount of data, but the key management is difficult.
- Asymmetric key encryption system , also known as public key encryption. It needs to use different keys to complete the encryption and decryption operations, one is publicly released, that is, the public key, and the other is kept secretly by the user, that is, the private key. The sender of the message uses the public key to encrypt it, and the receiver of the message uses the private key to decrypt it. The public key mechanism is flexible, but encryption and decryption are much slower than symmetric key encryption.
- Therefore, in practical applications, people usually combine the two together. For example, a symmetric key encryption system is used to store a large amount of data information, and a public key encryption system is used to encrypt keys.
- For ordinary symmetric cryptography, the encryption and decryption operations use the same key. Generally, the symmetric encryption algorithm used is relatively simple and efficient, the key is short, and it is extremely difficult to decipher. Since the confidentiality of the system mainly depends on the security of the key, the secure transmission and storage of the key on the public computer network is Grim question. It is precisely because both parties use the same key in symmetric cryptography, so functions such as data signature and non-repudiation cannot be achieved.
- Since the 1970s, some scholars have proposed the public key system, which uses the mathematical principle of one-way functions to achieve the separation of encryption and decryption keys. The encryption key is public and the decryption key is kept secret. This new cryptosystem has aroused widespread attention and discussion in the cryptography community.
- Unlike ordinary symmetric cryptography, which uses the same key to encrypt and decrypt data, asymmetric key encryption technology uses a pair of matching keys to encrypt and decrypt. There are two keys, one is a public key and the other is a private key. They have this property: each key performs a kind of one-way processing of the data, and the function of each is exactly the opposite of the other. When one is used for encryption, the other is used for decryption. Files encrypted with a public key can only be decrypted with a private key, while files encrypted with a private key can only be decrypted with a public key. The public key is made public by its owner, and the private key must be kept secret. In order to send a confidential message, the sender must use the receiver's public key to encrypt the data. Once encrypted, only the receiver can use its private key to decrypt it. Conversely, users can process data with their own private keys. In other words, the work of the key pair is optional. This provides the basis for a "digital signature". If a user is required to process the data with his own private key, others can use the public key provided by him to process the data. Since only the owner knows the private key, this processed message forms an electronic signature-a file that others cannot generate. The digital certificate contains public key information, which confirms the identity of the user who owns the key pair.
- A simple example of a public key can be represented by a prime number. The algorithm for multiplying prime numbers is used as the public key. The algorithm that solves the resulting multiplied integral into the original prime number is the private key. Encryption is to add the prime number to the information you want to pass. After encoding, it is transmitted to the recipient. After anyone receives this information, if there is no private key owned by the recipient, the decryption process (actually the process of finding prime numbers) will be due to the process of finding prime numbers (decomposition quality Factor) is too long to interpret the information.