License java

public abstract class MyRSACoder {
	public static final String KEY_ALGORITHM = "RSA";
	public static final String KEY_PROVIDER = "BC";
	public static final String SIGNATURE_ALGORITHM = "SHA1WithRSA";

	/**
	 * 初始化密钥对
	 */
	public static Map<String, Object> initKeys(String seed) throws Exception {
		
		Map<String, Object> keyMap = new HashMap<String, Object>();
		Security.addProvider(new BouncyCastleProvider());
		KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(KEY_ALGORITHM,KEY_PROVIDER);
		
		keyPairGenerator.initialize(1024,new SecureRandom(seed.getBytes()));
		KeyPair pair = keyPairGenerator.generateKeyPair();
		RSAPublicKey rsaPublicKey = (RSAPublicKey) pair.getPublic();
		RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) pair.getPrivate();
		
		KeyFactory factory = KeyFactory.getInstance(KEY_ALGORITHM,KEY_PROVIDER);
		RSAPublicKeySpec pubKeySpec = new RSAPublicKeySpec(new BigInteger(rsaPublicKey.getModulus().toString()),new BigInteger(rsaPublicKey.getPublicExponent().toString()));
		RSAPrivateKeySpec priKeySpec = new RSAPrivateKeySpec(new BigInteger(rsaPrivateKey.getModulus().toString()),new BigInteger(rsaPrivateKey.getPrivateExponent().toString()));
		
		PublicKey publicKey = factory.generatePublic(pubKeySpec);
		PrivateKey privateKey = factory.generatePrivate(priKeySpec);

		System.out.println("公钥：" + pubKeySpec.getModulus() + "----" + pubKeySpec.getPublicExponent());
		System.out.println("私钥：" + priKeySpec.getModulus() + "----" + priKeySpec.getPrivateExponent());
		keyMap.put("publicKey", publicKey);
		keyMap.put("privateKey", privateKey);
		
		return keyMap;
	}
	
	/**
	 * 私钥加密
	 * */
	public static byte[] encryptRSA(byte[] data,PrivateKey privateKey) throws Exception {
		
		Cipher cipher = Cipher.getInstance(KEY_ALGORITHM,KEY_PROVIDER);
		cipher.init(Cipher.ENCRYPT_MODE, privateKey);
		int dataSize = cipher.getOutputSize(data.length);
		int blockSize = cipher.getBlockSize();
		int blockNum = 0;
		if (data.length % blockSize == 0) {
			blockNum = data.length / blockSize;
		} else {
			blockNum = data.length / blockSize + 1;
		}
		byte[] raw = new byte[dataSize * blockNum];
		int i = 0;
		while (data.length - i * blockSize > 0) {
			if (data.length - i * blockSize > blockSize) {
				cipher.doFinal(data, i * blockSize, blockSize, raw, i * dataSize);
			} else {
				cipher.doFinal(data, i * blockSize, data.length - i * blockSize, raw, i * dataSize);
			}
			i++;
		}
		
		return raw;
	}
	
	/**
	 * 生成数字签名
	 * */
	public static String sign(byte[] encoderData,PrivateKey privateKey) throws Exception {
		
		Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM,KEY_PROVIDER);
		sig.initSign(privateKey);
		sig.update(encoderData);
		
		return new String(Base64.encode(sig.sign()));
	}
	
	/**
	 * 校验数字签名
	 * */
	public static boolean verify (byte[] encoderData,String sign,PublicKey publicKey) throws Exception {
		
		Signature sig = Signature.getInstance(SIGNATURE_ALGORITHM,KEY_PROVIDER);
		sig.initVerify(publicKey);
		sig.update(encoderData);
		
		return sig.verify(Base64.decode(sign));
	}

main

public class MyRSACoderTest {

	public static void main(String[] args) throws Exception {
		
		Map<String, Object> keyMap = MyRSACoder.initKeys("0");
		PublicKey publicKey = (PublicKey) keyMap.get("publicKey");
		PrivateKey privateKey = (PrivateKey) keyMap.get("privateKey");
		
		String str = "您好！";
		byte[] encoderData = MyRSACoder.encryptRSA(str.getBytes(), privateKey);
		String sign = MyRSACoder.sign(encoderData, privateKey);
		boolean status = MyRSACoder.verify(encoderData, sign, publicKey);
		
		System.out.println("原文：" + str);
		System.out.println("密文：" + new String(encoderData));
		System.out.println("签名：" + sign);
		System.out.println("验证结果：" + status);
	}
}

java中使用公钥加密私钥解密原理实现license控制
现在很多J2EE应用都采用一个license文件来授权系统的使用，特别是在系统购买的早期，会提供有限制的license文件对系统进行限制，比如试用版有譬如IP、日期、最大用户数量的限制等。而license控制的方法又有很多，目前比较流行，只要设计的好就很难破解的方法就是采用一对密匙（私匙加密公匙解密）来生成License文件中的Sinature签名内容，再通过Base64或Hex来进行编码。比如原BEA公司现在是Oracle公司的WebLogic就采用的是这种方法来设置License文件。 
这里只进行一个比较简单的实现： 
一共三个类： 
A.KeyGenerater类生成公钥私钥对 
B.Signaturer类使用私钥进行签名 
C.SignProvider类用公钥验证