RSA Asymmetric Encryption Decryption instance

string content =  ""; for (int i=1;i<100;i++) content += i +  ")   Easy to say, hard to do.\n ";/*1, using public key encryption to file */{    /* 1) Reverse-construct the Publickkey object according to the public key, using */    string key_public  =  when calling cipher's Init method " mfwwdqyjkozihvcnaqebbqadswawsajbaiv38xxk06as11ocwq0ipqoqamz20zie8t5keamtubhzukgntaqygapua71r/ ineednsyyqs4pt6eawtjjop2rccaweaaq== ";     x509encodedkeyspec keyspec = new  x509encodedkeyspec (New base64decoder (). Decodebuffer (Key_public));     publickey  key = keyfactory.getinstance ("RSA"). Generatepublic (KeySpec);         cipher cipher = cipher.getinstance ("RSA");//rsa/ecb/pkcs1padding     cipher.init (Cipher.encrypt_mode, key);    /*      *  Direct encryption, because the content is too long will have an exception, need chunked encryption      * javax.crypto.illegalblocksizeexception: data must not be longer  Than 53 bytes     * cipher.dofinal (Content.getbytes ());   &NBSP;&NBSP;&NBSP;*/&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;/*2) chunked encryption, with keypairgenerator.initialize (int  keysize), the keysize used in this example is 512*/    int blocksize = 53;// Cipher.getblocksize () is 0? 53    byte[] encryptbyte = content.getbytes ();    based on the exception prompt  //is divided by block size, the portion of the less piece is a piece of     int blocksNum =  (int) Math.ceil (1.0* encryptbyte.length)/blocksize);        fileoutputstream out  = new fileoutputstream ("License.lic");    for  (int i = 0;  i < blocksnum; i++)  {        if  (i  < blocksnum - 1)  {            out.write ( Cipher.dofinal (encryptbyte, i * blocksize, blocksize));         } else {             Out.write (Cipher.dofinal (encryptbyte, i * blocksize, encryptbyte.length - i  * blocksize));        }    }         out.close ();} /*2, using the private key to decrypt */{    /*1 from a file) Privatekey object is constructed according to the private key */    string key_ private =  "miibvaibadanbgkqhkig9w0baqefaascat4wgge6ageaakeai/ fzfettoczxu4jarqg9chacbpbrmitxpkp5oxnruhnsqy1mbdkacm5rvvh8g14qm2zljblg9porpzomminatwidaqabakbqdar7fbjbc15hgsqecv194d9wo3l 18dot9fnqgpsrogvyiviizp1/ Wihpmtn6uhwsoazqcoqv33gxlf6fkbwxaieav390q3x2cbjescxhnbqpiospe9ryd3ewsajn6q7ud7uciqc7htuzelhmcpV4xpzg6e1qzkwhbfuqkhg9aoeaniw0owiglw5tat3fhxqg4ek29sq34ufjcwjuuxcrljatqcl9gdeciqchqe+ Jzrxdbvsrcy9vb83jleo2hwpucjto24dbahsopwigev547ycgz+pyi1dnqhiljiifif+h1abzaih5mrkshtw= ";     pkcs8encodedkeyspec keyspec = new pkcs8encodedkeyspec (New BASE64Decoder (). Decodebuffer (key_private));     privatekey key = keyfactory.getinstance ("RSA "). Generateprivate (KeySpec);        cipher cipher =  Cipher.getinstance ("RSA");//rsa/ecb/pkcs1padding    cipher.init (Cipher.DECRYPT_MODE,  key);         /*2) block decryption, based on the size of each encrypted output to determine */     Fileinputstream cis = new fileinputstream ("License.lic");     Bytearrayoutputstream bos = new bytearrayoutputstream ();     /* encrypt time block encryption, Encrypted output result size fixed */    byte[] data = neW byte[cipher.getoutputsize (Cis.available ())];    int len = 0;     while ((Len = cis.read (data))  > 0) {         bos.write (Cipher.dofinal (Data, 0, len));    }     cis.close ();         system.out.print (New String ( Bos.tobytearray ()));}

RSA Asymmetric Encryption Decryption instance