java處理加密文件---RSA加密和解密

 public class RSA {
 public static void main(String []args)throws Exception
    {
  String ptext = "he";
  //獲取公鑰生成參數
  KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
  kpg.initialize(1024);
  KeyPair keyPair = kpg.genKeyPair();

RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
  RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
System.out.println("公共碼"+publicKey.getModulus().toString());
byte[] ptexts = ptext.getBytes("UTF8");
  BigInteger m = new BigInteger(ptexts);
  BigInteger c = m.modPow(publicKey.getPublicExponent(), publicKey.getModulus());
  System.out.println("密文"+c);
//System.out.println("d："+privateKey.getPrivateExponent());
System.out.println("私密碼"+privateKey.getModulus());
BigInteger jm=c.modPow(privateKey.getPrivateExponent(), privateKey.getModulus());
  System.out.println("解碼數據"+jm);
byte[] mt =jm.toByteArray();
System.out.print("解碼結果");
  for(int i=0;i<mt.length;i++){
   System.out.print((char)mt[i]);
  }

}

}</pre>