Type of encryption and its related algorithm-symmetric encryption

In the previous section we talked about the three aspects of encryption:confidentiality, integrity, authentication

In order to achieve the communication between A and B is confidential, so that the third party even if intercepted information can not be understood, it is necessary to encrypt the plaintext data.

We know that encryption is actually implemented using some algorithms ( which is why the relationship between computers and mathematicians is so close that computers are all kinds of logical operations ^_^). For example, the simplest algorithm, such as the A-E to move 5 bits into f-j, then decryption is to move to the left 5 bits, so that encryption and decryption using the same set of algorithms called symmetric encryption algorithm .

For example, have you ever seen the Navajo code in the "Wind language", "fighter" is called "da-ha-xi" (Dah-he-tih-hi), Navajo meaning "hummingbird"; "dive bombers" are called "guineas" and Mean "kitty". There is a password control book.

Example:

[Email protected] ~]# cat/etc/issue \s Kernel \ r on an \m [Email protected] ~]# Cat/etc/issue | TR "A-E" "F-j" \s KJRnJl \ r on fN \m

Some algorithms can be easily cracked, then there will be a problem, the development of an algorithm cost is very high ( to consider the algorithm itself is cracked the need for conditions, but also to consider the future of the computer 10 years, the development of the 20, can be violent cracking and other issues ), it is impossible for everyone to use a set of algorithms, And some algorithms are public, so if the algorithm and password (key) can be combined to encrypt, at least the replacement password (key) cost is much lower than the algorithm itself.

Suppose a symmetric encryption algorithm is used between A and B and a string of passwords (keys) is negotiated: 123456, so that communication between A and B is confidential.

but the problem again , A and B communication between the confidentiality is guaranteed, but a and c,a and d,a even with more machines need to communicate, 50, 100, if the host with the communication to negotiate a password, light maintenance password table is a very difficult thing. If a communicates with other machines using the same algorithm and password, the malicious e learns that A and B are entering into a very important contract, using the password of the communication before A and e, and tampering with the contract between A and b through various means, resulting in a loss of a heavy weight.

Symmetric encryption can solve the confidentiality of the communication, but the integrity of the information can not be guaranteed, then how to ensure the integrity of the information? After a is sent to B, B can verify by some means that the received information has not been tampered with or otherwise prevented from verifying the integrity of the information. For more information, please listen to tell. ^_^

Types of encryption and their associated algorithms-symmetric encryption