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Recently, in the process of contact with Hadoop, the public key and the private key is not clear, write a blog to learn.Encryption and authenticationencryption is the encryption of data, so that illegal users, even if the encrypted data can not obtain the correct information content, so data encryption to protect data, prevent monitoring attacks. The focus is on the security of the data.Identity Authenticat

Both the Primary key and the unique key are unique constraints. But there's a big difference:1, Primary key 1 or more columns must be NOT NULL, if column is null, when the Primary key is added, the columns are automatically changed to NOT NULL. The unique KEY does not have t

MySQL Learning (4) -- foreign key, mysql learning foreign key 1. For example, there are two tables: "Classification Table" and "commodity table". To indicate the category of a commodity, we usually add a column to the commodity table, used to store information about the cid type. This column is called a foreign key. In this case, the category table category i

Produkey is a 56K full English free software that opens directly under Windows system to see the product installation keys for Office 20XX and Windows X (Activation key). I believe there is no simpler way to view windows and Office installation keys (activation keys) than this software. Windows version and Activation key is visible after opening Produkey Nobody knows how to open produkey, do they? 1, the

Performance Analysis of Oracle primary keys and composite primary keys. Primary keys and composite primary keys have the same query performance (the same index height and the appropriate use of indexes ). Primary Key and composite primary key, (update, in Performance Analysis of Oracle primary keys and composite primary keys. Primary keys and composite primary keys have the same query performance (the same

Tags: style blog http color using strong data forIf a field of one entity points to the primary key of another entity, it is called a foreign keyThe entity that is pointed to is called the primary entity (the primary table), also called the parent entity (the parent table).The entity that is responsible for pointing, called from the entity (from the table), also called the Child Entity (sub-table)Role:Used to constrain entities that are within a relat

Primary key:A property or property group that uniquely identifies a row in a table. A table can have only one primary key, but there may be multiple candidate indexes. Primary keys often form referential integrity constraints with foreign keys, preventing data inconsistencies. The primary key guarantees that the record is unique and the primary key domain is not

Tags: com CLR database optimization multiple date let person altPRIMARY KEY constraint A table typically has a column or set of columns that contains values that uniquely identify each row in the table. Such a column or columns is called the primary key (PK) of the table and is used to enforce the entity integrity of the table. Because primary KEY constraints gua

Generally, when you log on to the remote server through ssh, use password authentication and enter the user name and password respectively. The two can log on only when they meet certain rules. However, password authentication has the following Disadvantages: The user cannot set a blank password (even if the system allows a blank password, it is very dangerous)Passwords are easy to peek at or guess.If an account on the server is to be used by multiple users, all users must know the password, whi

"Asymmetric Encryption Algorithm". (1) Party B generates two keys (public and private). 　　The public key is public and can be obtained by anyone, and the private key is confidential. (2Party A obtains the public key of party B, then uses it to encrypt the information. (3Party B obtains the encrypted information and decrypts it with the private

Symmetric key encryption in HTTPS, public key encryption, digital certificate keyWe call unencrypted content plaintext, and the encrypted content is called ciphertext.In short, to encrypt a piece of plaintext, you can enter this content into an encryption function, output ciphertext. However, this simple encryption method has been stolen into the cryptographic function to crack the danger of clear text, and

Today saw a bit about the public key encryption of the content, quickly write down the province's forgotten.Here are a few concepts: public key, private key, encryption, authentication, authentication Center (CA), digital certificate.Public and private keys are asymmetric encryption, and the public and private keys are completely different, but correspond to each

a game or looking at something shameful, the boss comes in! The mouse suddenly point to the lower right corner of the display desktop, how to do? Take it easy! Press the Windows key and the D key directly, look, the desktop flashes!4. A little gimmick, pretty flashy. Press the Windows key to press and then press the TAB key