公有例子

package javasecurity;
import java.security.*;
import javax.crypto.*;
// 用RSA公钥算法进行加密
public class PublicExample
{
public static void main(String[] args) throws Exception
{
if (args.length != 1)
{
System.err.println("Usage: java PublicExample text");
System.exit(1);
}
byte[] plainText = args[0].getBytes("UTF8");
// 生成RAS密钥
System.out.println("\nStart generating RSA key");
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(1024);
KeyPair key = keyGen.generateKeyPair();
System.out.println("Finish generating RSA key");
// 得到RSA cipher 对象，同是打印出算法的提供者  
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
System.out.println("\n" + cipher.getProvider().getInfo());
// 使用公钥对明文进行加密
System.out.println("\nStart encryption");
cipher.init(Cipher.ENCRYPT_MODE, key.getPublic());
byte[] cipherText = cipher.doFinal(plainText);
System.out.println("Finish encryption: ");
System.out.println(new String(cipherText, "UTF8"));
// 使用私钥对加密密文进行解密
System.out.println("\nStart decryption");
cipher.init(Cipher.DECRYPT_MODE, key.getPrivate());
byte[] newPlainText = cipher.doFinal(cipherText);
System.out.println("Finish decryption: ");
System.out.println(new String(newPlainText, "UTF8"));
}
}