//获取秘钥对
　　　　public static KeyPair getKeyPair() throws Exception{
		KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
		keyPairGenerator.initialize(1024);
		return keyPairGenerator.generateKeyPair();
	}
	//获取公钥
	public static PublicKey getpublicKey() throws Exception{
		Key key = getKeyPair().getPublic();
		byte[] bytes = key.getEncoded();
		byte[] bytesbase64 = Base64.encodeBase64(bytes);
		X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(bytesbase64);
        KeyFactory keyFactory = KeyFactory.getInstance("RSA"); 
        PublicKey publicKeynew = keyFactory.generatePublic(x509KeySpec);
        return publicKeynew;
	}
　　　　//获取私钥
	public static PrivateKey getprivateKey() throws Exception{
		Key key = getKeyPair().getPublic();
		byte[] bytes = key.getEncoded();
		byte[] bytesbase64 = Base64.encodeBase64(bytes);
		PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(bytesbase64); 
        KeyFactory keyFactory = KeyFactory.getInstance("RSA"); 
        PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec);
        return privateKey;
	}
	//对正文进行数字签名
	private static byte[] sign(byte[] content, PrivateKey privateKey) throws Exception{
		MessageDigest md = MessageDigest.getInstance("MD5");
		byte[] bytes = md.digest(content);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, privateKey);
		return cipher.doFinal(bytes);
	}
　　　　//对正文进行数字签名认证
	private static boolean verify(byte[] content,PublicKey publicKey, byte[] sign) throws Exception{
		MessageDigest md = MessageDigest.getInstance("MD5");
		byte[] bytes = md.digest(content);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, publicKey);
		byte[] signbyte = cipher.doFinal(bytes);
		byte[] base64 = Base64.encodeBase64(bytes);
		byte[] base64new = Base64.encodeBase64(bytes);
		if(base64.equals(base64new)){
			return true;
		}else{
			return false;
		}
	}

	private static byte[] signnew(byte[] content, PrivateKey privateKey) throws Exception{
		Signature signature = Signature.getInstance("MD5withRSA");
		signature.initSign(privateKey);
		signature.update(content);
		return signature.sign();
	}
	private static boolean verifynew(byte[] content, PublicKey publicKey, byte[] sign) throws Exception{
		Signature signature = Signature.getInstance("MD5withRSA");
		signature.initVerify(publicKey);
		signature.update(content);
		return signature.verify(sign);
	}

	private static byte[] signsha(byte[] content,PrivateKey privateKey) throws Exception{
		MessageDigest md = MessageDigest.getInstance("SHA1");
		byte[] bytes = md.digest(content);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.ENCRYPT_MODE, privateKey);
		return cipher.doFinal(bytes);
	}
	
	private static boolean verifysha(byte[] content,byte[] bytesha, PublicKey publicKey) throws Exception{
		MessageDigest md = MessageDigest.getInstance("SHA1");
		byte[] bytes = md.digest(content);
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.DECRYPT_MODE, publicKey);
		byte[] byteshanew = cipher.doFinal(bytesha);
		byte[] bytebase64 = Base64.encodeBase64(bytes);
		byte[] bytebase64new = Base64.encodeBase64(byteshanew);
		if(bytebase64.equals(bytebase64new)){
			return true;
		}else {
			return false;
		}
	}

	private static byte[] signShawithRSA(byte[] content,PrivateKey privateKey) throws Exception{
		Signature signature = Signature.getInstance("SHA1withRSA");
		signature.initSign(privateKey);
		signature.update(content);
		return signature.sign();
	}
	
	private static boolean verifyShawithRSA(byte[] content,byte[] bytersa,PublicKey publicKey) throws Exception{
		Signature signature = Signature.getInstance("SHA1withRSA");
		signature.initVerify(publicKey);
		signature.update(content);
		return signature.verify(bytersa);
	}