1.随机生成密钥对
/**
* 随机生成密钥对
* @throws NoSuchAlgorithmException
*/
public static void genKeyPair() throws NoSuchAlgorithmException {
// 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();
// 得到私钥
RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
// 得到公钥
RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
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
//0表示公钥
keyMap.put(0,publicKeyString);
//1表示私钥
keyMap.put(1,privateKeyString);
}
2.RSA公钥加密
/**
* 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 encrypt( String str, String publicKey ) throws Exception{
try {
//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);
byte[] strBytes = str.getBytes("UTF-8");
int inputLength = strBytes.length;
System.out.println("加密字节数：" + inputLength);
// 最大加密字节数，超出最大字节数需要分组加密
// 标识
int offSet = 0;
byte[] resultBytes = {};
byte[] cache;
while (inputLength - offSet > 0) {
if (inputLength - offSet > MAX_ENCRYPT_BLOCK) {
cache = cipher.doFinal(strBytes, offSet, MAX_ENCRYPT_BLOCK);
offSet += MAX_ENCRYPT_BLOCK;
} else {
cache = cipher.doFinal(strBytes, offSet, inputLength - offSet);
offSet = inputLength;
}
resultBytes = Arrays.copyOf(resultBytes, resultBytes.length + cache.length);
System.arraycopy(cache, 0, resultBytes, resultBytes.length - cache.length, cache.length);
}
String outStr = Base64.encodeBase64String(resultBytes);
return outStr;
}catch (Exception e){
System.out.println("rsaEncrypt error:" + e.getMessage());
}
return "";
}
3.RSA私钥解密
/**
* 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 decrypt(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);
ByteArrayOutputStream out = new ByteArrayOutputStream();
int inputLen = inputByte.length;
System.out.println("解密字节数：" + inputLen);
int offset = 0;
byte[] cache;
int i = 0;
// 对数据分段解密
while (inputLen - offset > 0) {
if (inputLen - offset > MAX_DECRYPT_BLOCK) {
cache = cipher.doFinal(inputByte, offset, MAX_DECRYPT_BLOCK);
} else {
cache = cipher.doFinal(inputByte, offset, inputLen - offset);
}
out.write(cache, 0, cache.length);
i++;
offset = i * MAX_DECRYPT_BLOCK;
}
byte[] decryptedData = out.toByteArray();
out.close();
// 解密后的内容
String outStr = new String(decryptedData);
return outStr;
}
4.使用
private static final Map<Integer,String> keyMap=new HashMap<>();
/**
* RSA最大加密明文大小
*/
private static final int MAX_ENCRYPT_BLOCK = 117;
/**
* RSA最大解密密文大小
*/
private static final int MAX_DECRYPT_BLOCK = 128;
/**
* @param args
* @throws Exception
*/
public static void main(String[] args) throws Exception {
//生成公钥和私钥
genKeyPair();
//加密字符串
String message = "sdaw";
System.out.println("随机生成的公钥为:" + keyMap.get(0));
System.out.println("随机生成的私钥为:" + keyMap.get(1));
String messageEn = encrypt(message,keyMap.get(0));
System.out.println(message + "\t加密后的字符串为:" + messageEn);
String messageDe = decrypt(messageEn,keyMap.get(1));
System.out.println("还原后的字符串为:" + messageDe);
}
