RSA非对称加密

RSA非对称加密

public static void main(String[] args) throws Exception {
String content = "也不会反对呀发神经的沙发上的快感";
//非对称加密用公钥加密
KeyPairGenerator pairGenerator = KeyPairGenerator.getInstance("RSA");
//得到秘钥对
KeyPair keyPair = pairGenerator.generateKeyPair();

//获取公钥
PublicKey publicKey = keyPair.getPublic();

String encryptData = encrypt(content, publicKey);//得到加密后的内容
System.out.println(encryptData);
//解密
String decryptData = decrypt(encryptData, privateKey);
System.out.println(decryptData);
}
/**
* 解密
* @param encryptData
* @param privateKey
* @return
*/
public static String decrypt(String encryptData,PrivateKey privateKey)throws Exception{
byte[] bytes = Base64.getDecoder().decode(encryptData);
//获取cipher单例对象
Cipher cipher = Cipher.getInstance("RSA");
//初始化解密，传入私钥
cipher.init(Cipher.DECRYPT_MODE, privateKey);
//正式解密    Data must not be longer than 128 bytes

//byte[] decryptBytes = cipher.doFinal(bytes);//生成加密后的字节数组
byte[] decryptBytes = doFinalWithBlock(cipher, bytes, 128);
return new String(decryptBytes);
}

/**
* 加密方法
* @param content
* @param publicKey
* @return
*/
public static String encrypt(String content,PublicKey publicKey)throws Exception{
//获取cipher单例对象
Cipher cipher = Cipher.getInstance("RSA");
//初始化加密，传入公钥
cipher.init(Cipher.ENCRYPT_MODE, publicKey);
//正式加密,一次性加密数据的长度不能超过117个字节！
//byte[] encryptBytes = cipher.doFinal(content.getBytes());//生成加密后的字节数组
byte[] bytes = content.getBytes();
byte[] encryptBytes = doFinalWithBlock(cipher, bytes,117);
return Base64.getEncoder().encodeToString(encryptBytes);
}

/**
* 分块来对大数据进行加密解密
* @param cipher
* @param bytes
* @param max
* @return
* @throws IllegalBlockSizeException
* @throws BadPaddingException
* @throws IOException
*/
private static byte[] doFinalWithBlock(Cipher cipher, byte[] bytes,int max)
throws IllegalBlockSizeException, BadPaddingException, IOException {
int length = bytes.length;//要加密的字节数组的长度
int inputOffset = 0;//开始加密的位置
ByteArrayOutputStream baos = new ByteArrayOutputStream();
while(inputOffset < length){//如果要开始加密的位置比bytes的长度大了就说明全部加密完了
if (length - inputOffset >= max) {
byte[] encryptBytes = cipher.doFinal(bytes, inputOffset, max);
//每次加密得到字节数组就写入字节数组输出流中
baos.write(encryptBytes);
inputOffset += max;
}else {
//说明剩下的字节长度小于117，全部加密完剩下的所有字节
byte[] encryptBytes = cipher.doFinal(bytes, inputOffset, length - inputOffset);
baos.write(encryptBytes);
inputOffset = length;
}
}
byte[] encryptBytes = baos.toByteArray();
return encryptBytes;
}