简单完整的代码，通过这个代码你将对RSA加密算法在Java中的实现方法有一个初步的了解，这个类，你可以直接使用，水平高的，就自己修改完善下代码。

package security;
import java.security.*;
import java.security.spec.*;
import java.security.interfaces.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;
import java.io.*;
import java.math.*;
public class RSADemo {
public RSADemo() {
}
public static void generateKey() {
try {
KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(1024);
KeyPair kp = kpg.genKeyPair();
PublicKey pbkey = kp.getPublic();
PrivateKey prkey = kp.getPrivate();
// 保存公钥
FileOutputStream f1 = new FileOutputStream("pubkey.dat");
ObjectOutputStream b1 = new ObjectOutputStream(f1);
b1.writeObject(pbkey);
// 保存私钥
FileOutputStream f2 = new FileOutputStream("privatekey.dat");
ObjectOutputStream b2 = new ObjectOutputStream(f2);
b2.writeObject(prkey);
} catch (Exception e) {
}
}
public static void encrypt() throws Exception {
String s = "Hello World!";
// 获取公钥及参数e,n
FileInputStream f = new FileInputStream("pubkey.dat");
ObjectInputStream b = new ObjectInputStream(f);
RSAPublicKey pbk = (RSAPublicKey) b.readObject();
BigInteger e = pbk.getPublicExponent();
BigInteger n = pbk.getModulus();
System.out.println("e= " + e);
System.out.println("n= " + n);
// 获取明文m
byte ptext[] = s.getBytes("UTF-8");
BigInteger m = new BigInteger(ptext);
// 计算密文c
BigInteger c = m.modPow(e, n);
System.out.println("c= " + c);
// 保存密文
String cs = c.toString();
BufferedWriter out =
new BufferedWriter(
new OutputStreamWriter(new FileOutputStream("encrypt.dat")));
out.write(cs, 0, cs.length());
out.close();
}
public static void decrypt() throws Exception {
// 读取密文
BufferedReader in =
new BufferedReader(
new InputStreamReader(new FileInputStream("encrypt.dat")));
String ctext = in.readLine();
BigInteger c = new BigInteger(ctext);
// 读取私钥
FileInputStream f = new FileInputStream("privatekey.dat");
ObjectInputStream b = new ObjectInputStream(f);
RSAPrivateKey prk = (RSAPrivateKey) b.readObject();
BigInteger d = prk.getPrivateExponent();
// 获取私钥参数及解密
BigInteger n = prk.getModulus();
System.out.println("d= " + d);
System.out.println("n= " + n);
BigInteger m = c.modPow(d, n);
// 显示解密结果
System.out.println("m= " + m);
byte[] mt = m.toByteArray();
System.out.println("PlainText is ");
for (int i = 0; i < mt.length; i++) {
System.out.print((char) mt[i]);
}
}
public static void main(String args[]) {
try {
generateKey();
encrypt();
decrypt();
} catch (Exception e) {
System.out.println(e.toString());
}
}
}