Shulou(Shulou.com)06/01 Report--

Three well-known encryption algorithms:

Md5 (message-digest algorithm 5): converts a string of arbitrary length to a large integer of 128bit, and this transformation is an irreversible string transformation algorithm.

Typical applications: fingerprint a piece of information to prevent tampering. Digital signature application.

Md5 is widely used in encryption and decryption. In many systems, the user's password is saved as MD5. When the user logs into the system, the password entered by the user is compared with the password saved in the system according to the value of md5 encryption, to determine whether the password is entered correctly, but the system does not know what the user's password is.

RSA: named after the inventors: Ron rivest,adi shamir and Leonard adlemen. RSA is the first algorithm that can be used for both data encryption and digital signature. But it has not been proved in theory.

Des (data encryption standard): in January 1977, the United States government promulgated the adoption of IBM's dea as the official data encryption standard for unclassified data. At present, des algorithm is widely used in pos, atm, ic card, gas station, highway toll station and other fields, such as the encrypted transmission of pin of credit card holders, the two-way authentication of ic card and posmachine, the mac verification of financial transaction data packets and so on.

Principle of des algorithm:

There are three entry parameters for des algorithm: key,data,mode. Among them, key is 8 bytes and 64 bits, which is the key of des algorithm. Data is also 8 bytes and 64 bits, which is the data to be encrypted or decrypted. Mode is the working way of des: encryption or decryption.

If the same key value is agreed on by both sides of the communication, it can be transmitted safely and reliably. Change the key value periodically to improve security.

There is no more effective method except for using the exhaustive search method to perform the des algorithm.

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