The non-symmetric encryption DH algorithm for information encryption

Asymmetric encryption algorithm is relative to symmetric encryption algorithm, for symmetric encryption algorithm please refer to the previous summary, today for everyone to introduce the DH algorithm, DH is a key exchange algorithm, the receiver based on the sender encryption key, generate receiver decryption key. Let's take a look at the following:

Initialize Sender key:

Keypairgenerator sendkeypairgenerator = keypairgenerator.getinstance ("DH");            Sendkeypairgenerator.initialize (+);             = Sendkeypairgenerator.generatekeypair ();             byte [] Sendpublickeyenc = Sendkeypair.getpublic (). getencoded (); // generate sender Public key, send to receiver (network, file ...) )

Initialize the receiver key:

Keyfactory receiverkeyfactory = keyfactory.getinstance ("DH"); X509encodedkeyspec X509encodedkeyspec=NewX509encodedkeyspec (SENDPUBLICKEYENC); PublicKey Receivepublickey=receiverkeyfactory.generatepublic (X509ENCODEDKEYSPEC); Dhparameterspec Dhparameterspec=((Dhpublickey) receivepublickey). Getparams (); Keypairgenerator Receiverkeypairgenerator= Keypairgenerator.getinstance ("DH");            Receiverkeypairgenerator.initialize (DHPARAMETERSPEC); KeyPair Receiverkeypair=Receiverkeypairgenerator.generatekeypair (); Privatekey Receiverprivatekey=receiverkeypair.getprivate (); byte[] Receiverpublickeyenc = Receiverkeypair.getpublic (). getencoded ();

To build the receiver key:

Keyagreement receiverkeyagreement = keyagreement.getinstance ("DH");            Receiverkeyagreement.init (Receiverprivatekey);             true );                         = Receiverkeyagreement.generatesecret ("DES"); // Receiving Party key

To build the sender key:

Keyfactory sendkeyfactory = keyfactory.getinstance ("DH");             New X509encodedkeyspec (RECEIVERPUBLICKEYENC);             = Sendkeyfactory.generatepublic (x509encodedkeyspec);                         = Keyagreement.getinstance ("DH");            Sendkeyagreement.init (Sendkeypair.getprivate ());             true );                         = Sendkeyagreement.generatesecret ("DES"); // Sender Key

Sender-Side encryption:

Cipher Sendcipher = cipher.getinstance ("DES");            Sendcipher.init (Cipher.encrypt_mode, Senddeskey);             byte [] Sendresult = sendcipher.dofinal (src.getbytes ());            System.out.println ("Sendresult:" +hex.encodehexstring (Sendresult));

Receiver decryption:

Cipher Receivercipher = cipher.getinstance ("DES");            Receivercipher.init (Cipher.decrypt_mode, Receiverdeskey);             byte [] Receiverresult = receivercipher.dofinal (sendresult);            System.out.println ("Receiverresult:" +new String (Receiverresult));

The Asymmetric Encryption Algorithm (DH) based on key exchange is summed up here.

The non-symmetric encryption DH algorithm for information encryption