DES algorithm
DES(Data Encryption Standard) is a classical symmetric algorithm. Its data packet length is 64 bits, the used key is 64 bits, and the effective key length is 56 bits (8 bits are used for parity check). It was developed by IBM in the 197s, screened by the government's encryption standards, adopted by the US government in November 1976, and subsequently recognized by the US National Bureau of Standards and the American National Standard Institute (ANSI).
AES algorithm
In January p>1997, the National Institute of Standards and Technology (NIST) announced the collection of new encryption algorithms. On October 2nd, 2, Rijndael algorithm designed by Belgian designers Joan Daemen and Vincent Rijmen finally won the victory with its excellent performance and anti-attack ability, and became a new generation of encryption standard AES(Advanced Encryption Standard).
MD5
The full name of MD5 is message-digest algorithm 5, which was developed by MIT Laboratory for Computer Science and ronald l. rivest of rsa data security inc in the early 199s, and developed by md2, md3 and md4. Its function is to make large-capacity information "compressed" into a secure format before signing a private key with digital signature software (that is, to transform a byte string of arbitrary length into a large integer with a certain length). Whether md2, md4 or md5, they all need to get a random length of information and generate a 128-bit information digest. Although the structures of these algorithms are more or less similar, the design of md2 is completely different from that of md4 and md5, because md2 is optimized for 8-bit machines, while md4 and md5 are designed for 32-bit computers. The descriptions of these three algorithms and the source code of C language are described in detail in internet rfcs 1321.
RSA
RSA algorithm is an asymmetric cryptographic algorithm. The so-called asymmetry means that the algorithm needs a pair of keys. If one of them is used for encryption, the other one is needed for decryption.
RSA algorithm involves three parameters, n, e1 and e2.
where n is the product of two large prime numbers p and q, and the number of bits occupied in binary representation of n is the so-called key length.
e1 and e2 are a pair of related values, and e1 can be chosen arbitrarily, provided that e1 and (p-1)*(q-1) are coprime; Select e2 again, and require (e2*e1)mod((p-1)*(q-1))=1.
(n and e1),(n and e2) are the key pairs.
RSA encryption and decryption algorithms are exactly the same. If A is plaintext and B is ciphertext, then: A = b E1 mod n; B=A^e2 mod n；
e1 and e2 can be used interchangeably, that is,
a = b E2 mod n; B=A^e1 mod n；
Double-key encryption
Double-key technology is Public Key encryption (PKE) technology, which uses two keys, a public key and a Private Key. The former is used for encryption and the latter is used for decryption. This method is also called "asymmetric" encryption method, which solves the fundamental problem of traditional encryption method and greatly simplifies the workload of key distribution. Combined with traditional encryption methods, it can further enhance the reliability of traditional encryption methods. More prominently, digital signature can be realized by using public key encryption technology.
what is asymmetric encryption technology
in p>1976, American scholars Dime and Henman proposed a new key exchange protocol to solve the problems of public information transmission and key management, which allowed the two communication parties to exchange information on insecure media and reach a consistent key safely. This is the "public key system". Compared with symmetric encryption algorithm, this method is also called asymmetric encryption algorithm.