RSA
分段加密解密
当加密内容过长时会报错：Data must not be longer than xxx bytes
解决方案采取分段加密、解密方式来解决，具体代码如下：
import org.apache.commons.codec.binary.Base64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import java.io.UnsupportedEncodingException;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
public class RSAEncrypt {
private static final Logger log = LoggerFactory.getLogger(RSAEncrypt.class);
private static final String PUBLIC_KEY="publicKey";
private static final String PRIVATE_KEY="privateKey";
public static void main(String[] args) throws Exception {
//随机生成公钥和秘钥
Map<String, String> keyMap = genKeyPair();
System.out.println("公钥:\n"+keyMap.get(PUBLIC_KEY));
System.out.println("私钥:\n"+keyMap.get(PRIVATE_KEY));
String publicKey = keyMap.get(PUBLIC_KEY);
String privateKey = keyMap.get(PRIVATE_KEY);
//加密字符串
String message = "尊敬的旅客您好";
System.out.println("加密前的原数据:\n"+message);
String messageEn = publicKeyEncrypt(message, publicKey);
System.out.println("公钥加密后的数据:\n" + messageEn);
String messageDe = privateKeyDecrypt(messageEn, privateKey);
System.out.println("私钥解密后的数据:\n" + messageDe);
System.out.println("==========================================");
}
/**
* 功能描述:随机生成密钥对
* @return : java.util.Map
* 说明: key=publicKey value=公钥; key=privateKey value=私钥
*/
public static Map<String, String> genKeyPair() throws NoSuchAlgorithmException {
System.out.println("开始生成公钥私钥对\n");
// KeyPairGenerator类用于生成公钥和私钥对，基于RSA算法生成对象
KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");
// 初始化密钥对生成器，密钥大小为96-1024位
keyPairGen.initialize(1024, new SecureRandom());
// 生成一个密钥对，保存在keyPair中
KeyPair keyPair = keyPairGen.generateKeyPair();
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate(); // 得到私钥
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic(); // 得到公钥
// 得到公钥字符串
String publicKeyString = new String(Base64.encodeBase64(publicKey.getEncoded()));
// 得到私钥字符串
String privateKeyString = new String(Base64.encodeBase64((privateKey.getEncoded())));
// 将公钥和私钥保存到Map
Map<String, String> map = new HashMap<>();
map.put(PUBLIC_KEY, publicKeyString);
map.put(PRIVATE_KEY, privateKeyString);
return map;
}
/**
* RSA私钥加密
* @param str
* @param privateKey
* @return
* @throws Exception
*/
public static String privateKeyEncrypt(String str, String privateKey) throws Exception {
//base64编码的公钥
byte[] decoded = Base64.decodeBase64(privateKey);
PrivateKey priKey = KeyFactory.getInstance("RSA").
generatePrivate(new PKCS8EncodedKeySpec(decoded));
//RSA加密
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, priKey);
//当长度过长的时候，需要分割后加密 117个字节
byte[] resultBytes = getMaxResultEncrypt(str, cipher);
String outStr = Base64.encodeBase64String(resultBytes);
return outStr;
}
/**
* RSA公钥解密
* @param str
* @param publicKey
* @return
* @throws Exception
*/
public static String publicKeyDecrypt(String str, String publicKey) throws Exception {
//64位解码加密后的字符串
byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
//base64编码的私钥
byte[] decoded = Base64.decodeBase64(publicKey);
PublicKey pubKey = KeyFactory.getInstance("RSA")
.generatePublic(new X509EncodedKeySpec(decoded));
//RSA解密
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, pubKey);
//当长度过长的时候，需要分割后解密 128个字节
String outStr = new String(getMaxResultDecrypt(str, cipher));
return outStr;
}
/**
* RSA公钥加密
* @param str 加密字符串
* @param publicKey 公钥
* @return 密文
* @throws Exception 加密过程中的异常信息
*/
public static String publicKeyEncrypt(String str, String publicKey) throws Exception {
//base64编码的公钥
byte[] decoded = Base64.decodeBase64(publicKey);
RSAPublicKey pubKey = (RSAPublicKey) KeyFactory.getInstance("RSA").
generatePublic(new X509EncodedKeySpec(decoded));
//RSA加密
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE, pubKey);
//当长度过长的时候，需要分割后加密 117个字节
byte[] resultBytes = getMaxResultEncrypt(str, cipher);
String outStr = Base64.encodeBase64String(resultBytes);
return outStr;
}
/**
* 分段加密
* @param str
* @param cipher
* @return
* @throws IllegalBlockSizeException
* @throws BadPaddingException
*/
private static byte[] getMaxResultEncrypt(String str, Cipher cipher) throws IllegalBlockSizeException, BadPaddingException {
byte[] inputArray = str.getBytes();
int inputLength = inputArray.length;
// 最大加密字节数，超出最大字节数需要分组加密
int MAX_ENCRYPT_BLOCK = 117;
// 标识
int offSet = 0;
byte[] resultBytes = {};
byte[] cache = {};
while (inputLength - offSet > 0) {
if (inputLength - offSet > MAX_ENCRYPT_BLOCK) {
cache = cipher.doFinal(inputArray, offSet, MAX_ENCRYPT_BLOCK);
offSet += MAX_ENCRYPT_BLOCK;
} else {
cache = cipher.doFinal(inputArray, offSet, inputLength - offSet);
offSet = inputLength;
}
resultBytes = Arrays.copyOf(resultBytes, resultBytes.length + cache.length);
System.arraycopy(cache, 0, resultBytes, resultBytes.length - cache.length, cache.length);
}
return resultBytes;
}
/**
* RSA私钥解密
* @param str 加密字符串
* @param privateKey 私钥
* @return 铭文
* @throws Exception 解密过程中的异常信息
*/
public static String privateKeyDecrypt(String str, String privateKey) throws Exception {
//64位解码加密后的字符串
byte[] inputByte = Base64.decodeBase64(str.getBytes("UTF-8"));
//base64编码的私钥
byte[] decoded = Base64.decodeBase64(privateKey);
RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA")
.generatePrivate(new PKCS8EncodedKeySpec(decoded));
//RSA解密
Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, priKey);
// String outStr = new String(cipher.doFinal(inputByte));
//当长度过长的时候，需要分割后解密 128个字节
String outStr = new String(getMaxResultDecrypt(str, cipher));
return outStr;
}
/**
* 分段解密
* @param str
* @param cipher
* @return
* @throws IllegalBlockSizeException
* @throws BadPaddingException
* @throws UnsupportedEncodingException
*/
private static byte[] getMaxResultDecrypt(String str, Cipher cipher) throws IllegalBlockSizeException, BadPaddingException, UnsupportedEncodingException {
byte[] inputArray = Base64.decodeBase64(str.getBytes("UTF-8"));
int inputLength = inputArray.length;
// 最大解密字节数，超出最大字节数需要分组加密
int MAX_ENCRYPT_BLOCK = 128;
// 标识
int offSet = 0;
byte[] resultBytes = {};
byte[] cache = {};
while (inputLength - offSet > 0) {
if (inputLength - offSet > MAX_ENCRYPT_BLOCK) {
cache = cipher.doFinal(inputArray, offSet, MAX_ENCRYPT_BLOCK);
offSet += MAX_ENCRYPT_BLOCK;
} else {
cache = cipher.doFinal(inputArray, offSet, inputLength - offSet);
offSet = inputLength;
}
resultBytes = Arrays.copyOf(resultBytes, resultBytes.length + cache.length);
System.arraycopy(cache, 0, resultBytes, resultBytes.length - cache.length, cache.length);
}
return resultBytes;
}
}
