Java RSA encryption and decryption

From: http://java.chinaitlab.com/advance/798576_2.html

The code is not tested.

 

Import java. Security. Key;

Import java. Security. keyfactory;

Import java. Security. keypair;

Import java. Security. keypairgenerator;

Import java. Security. privatekey;

Import java. Security. publickey;

Import java. Security. Interfaces. rsw.vatekey;

Import java. Security. Interfaces. rsapublickey;

Import java. Security. spec. pkcs8encodedkeyspec;

Import java. Security. spec. x509encodedkeyspec;

Import javax. crypto. cipher;

Import sun. Misc. base64decoder;

Import sun. Misc. base64encoder;

Public class rsacoder {

/**

* Obtain the public key.

* @ Param key string (base64 encoded)

* @ Throws exception

*/

Public static publickey getpublickey (string key) throws exception {

Byte [] keybytes;

Keybytes = (New base64decoder (). decodebuffer (key );

X509encodedkeyspec keyspec = new x509encodedkeyspec (keybytes );

Keyfactory = keyfactory. getinstance ("RSA ");

Publickey = keyfactory. generatepublic (keyspec );

Return publickey;

}

/**

* Obtain the private key.

* @ Param key string (base64 encoded)

* @ Throws exception

*/

Public static privatekey getprivatekey (string key) throws exception {

Byte [] keybytes;

Keybytes = (New base64decoder (). decodebuffer (key );

Pkcs8encodedkeyspec keyspec = new pkcs8encodedkeyspec (keybytes );

Keyfactory = keyfactory. getinstance ("RSA ");

Privatekey = keyfactory. generateprivate (keyspec );

Return privatekey;

}

/**

* Obtain the key string (base64 encoded)

* @ Return

*/

Public static string getkeystring (Key key) throws exception {

Byte [] keybytes = key. getencoded ();

String S = (New base64encoder (). encode (keybytes );

Return S;

}

Public static void main (string [] ARGs) throws exception {

Keypairgenerator keypairgen = keypairgenerator. getinstance ("RSA ");

// Number of keys

Keypairgen. initialize (1024 );

// Key pair

Keypair = keypairgen. generatekeypair ();

// Public Key

Publickey = (rsapublickey) keypair. getpublic ();

// Private Key

Privatekey = (rsw.vatekey) keypair. getprivate ();

String publickeystring = getkeystring (publickey );

System. Out. println ("public: \ n" + publickeystring );

String privatekeystring = getkeystring (privatekey );

System. Out. println ("Private: \ n" + privatekeystring );

// Encryption/Decryption class

Cipher cipher = cipher. getinstance ("RSA"); // cipher. getinstance ("RSA/ECB/pkcs1padding ");

// Plaintext

Byte [] plaintext = "we are all very good! Email: @ Sina.com ". getbytes ();

// Encryption

Cipher. INIT (Cipher. encrypt_mode, publickey );

Byte [] enbytes = cipher. dofinal (plaintext );

// Obtain the key using the key string

Publickey = getpublickey (publickeystring );

Privatekey = getprivatekey (privatekeystring );

// Decrypt

Cipher. INIT (Cipher. decrypt_mode, privatekey );

Byte [] debytes = cipher. dofinal (enbytes );

Publickeystring = getkeystring (publickey );

System. Out. println ("public: \ n" + publickeystring );

Privatekeystring = getkeystring (privatekey );

System. Out. println ("Private: \ n" + privatekeystring );

String S = new string (debytes );

System. Out. println (s );

}

}