emmmmmm就是呢，我今天研究了一下非对称数据加密RSA的使用，算法什么的暂时不研究，加密算法还有很多，以后再研究吧，就酱(＞人＜;)。非对称加密算法需要两个密钥：公开密钥（publicKey）和私有密钥（privateKey）；如果用公有密钥加密，对应的就是要私有密钥才能解密；反过来就是私钥加密，公钥解密。
然后就来实现一下RSA加密的工具类吧
注意：RSA加密明文最大长度是117字节，解密要求密文最大长度为128字节，所以再加密和解密的时候要分段进行，就是每117字节就加密，然后再把这一节节拼起来。
1 public class RSAUtil {
2
3 public static String KEY_PAIRGENO = "RSA";
4 public static String PUBLIC_KEY = "PUBLIC_KEY";
5 public static String PRIVATE_KEY = "PRIVATE_KEY";
6 public static final String CHARSET = "UTF-8";
7
8 public static HashMap<String, String> keyMap = new HashMap<>(2);
9
10 public static void init() throws Exception {
11 KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_PAIRGENO);
12 keyPairGen.initialize(1024);
13 KeyPair keyPair = keyPairGen.generateKeyPair();
14 String publicKey = getPublicKeyStr(keyPair.getPublic());
15 String privateKey = getPrivateKeyStr(keyPair.getPrivate());
16
17 keyMap.put(PUBLIC_KEY, publicKey);
18 keyMap.put(PRIVATE_KEY,privateKey);
19 }
20
21
22 private static String getPrivateKeyStr(PrivateKey privateKey) throws Exception {
23 return Base64.encodeBase64URLSafeString(privateKey.getEncoded());
24 }
25
26 private static String getPublicKeyStr(PublicKey publicKey) throws Exception {
27 return Base64.encodeBase64URLSafeString(publicKey.getEncoded());
28 }
29
30 /**
31 * 把字符串公钥转为 RSAPublicKey 公钥
32 */
33 public static RSAPublicKey getPublicKey(String publicKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
34 //通过X509编码的Key指令获得公钥对象
35 KeyFactory keyFactory = KeyFactory.getInstance(KEY_PAIRGENO);
36 X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(Base64.decodeBase64(publicKey));
37 RSAPublicKey key = (RSAPublicKey) keyFactory.generatePublic(x509KeySpec);
38 return key;
39 }
40
41 /**
42 * 把字符串私钥转为 RSAPrivateKey 私钥
43 */
44 public static RSAPrivateKey getPrivateKey(String privateKey) throws NoSuchAlgorithmException, InvalidKeySpecException {
45 //通过PKCS#8编码的Key指令获得私钥对象
46 KeyFactory keyFactory = KeyFactory.getInstance(KEY_PAIRGENO);
47 PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(Base64.decodeBase64(privateKey));
48 RSAPrivateKey key = (RSAPrivateKey) keyFactory.generatePrivate(pkcs8KeySpec);
49 return key;
50 }
51
52 /**
53 * 公钥加密, 加密明文最大长度是117字节
54 */
55 public static String encryptByPublicKey(String msg, RSAPublicKey publicKey) throws Exception{
56 Cipher cipher = Cipher.getInstance(KEY_PAIRGENO);
57 cipher.init(Cipher.ENCRYPT_MODE,publicKey);
58 int keySize = publicKey.getModulus().bitLength();//1024
59 byte[] data = msg.getBytes(CHARSET);
60 byte[] encryptedData = rsaSplitCode(cipher, data, Cipher.ENCRYPT_MODE, keySize);
61 String mi= Base64.encodeBase64URLSafeString(encryptedData);
62 return mi;
63
64
65 }
66
67 /*
68 * 私钥解密，解密要求密文最大长度为128字节
69 * */
70 public static String decryptByPrivateKey(String rsaMsg, RSAPrivateKey privateKey) throws Exception{
71 Cipher cipher = Cipher.getInstance(KEY_PAIRGENO);
72 cipher.init(Cipher.DECRYPT_MODE, privateKey);
73 int keySize = privateKey.getModulus().bitLength();//长度是1024
74 byte[] data = Base64.decodeBase64(rsaMsg);
75 byte[] decryptedData = rsaSplitCode(cipher, data, Cipher.DECRYPT_MODE, keySize);
76 String ming = new String(decryptedData, CHARSET);
77 return ming;
78 }
79
80 /*私钥加密*/
81 public static String encryptByPrivate(String msg, RSAPrivateKey privateKey) throws Exception{
82 Cipher ciper = Cipher.getInstance(KEY_PAIRGENO);
83 ciper.init(Cipher.ENCRYPT_MODE,privateKey);
84 int keySize = privateKey.getModulus().bitLength();
85 byte[] data = msg.getBytes(CHARSET);
86 byte[] encryptedData = rsaSplitCode(ciper, data, Cipher.ENCRYPT_MODE,keySize);
87 String mi = Base64.encodeBase64URLSafeString(encryptedData);
88 return mi;
89 }
90
91 /*公钥解密*/
92 public static String decrytByPublic(String msg, RSAPublicKey publicKey) throws Exception{
93 Cipher ciper = Cipher.getInstance(KEY_PAIRGENO);
94 ciper.init(Cipher.DECRYPT_MODE, publicKey);
95 int keySize = publicKey.getModulus().bitLength();
96 byte[] data = Base64.decodeBase64(msg);
97 byte[] decryptedData = rsaSplitCode(ciper, data, Cipher.DECRYPT_MODE,keySize);
98 String ming = new String(decryptedData,CHARSET);
99 return ming;
100 }
101
102
103
104 private static byte[] rsaSplitCode(Cipher cipher, byte[] data,int opmode ,int keySize){
105 int maxBlock = 0;
106 if(opmode == Cipher.DECRYPT_MODE)
107 maxBlock = keySize / 8;//解密要求最大长度是128
108 else
109 maxBlock = keySize / 8 -11; //加密要求最大长度是117
110
111 int inputLen = data.length;
112 ByteArrayOutputStream out = new ByteArrayOutputStream();
113 int offSet = 0;
114 byte[] cache;
115 int i = 0;
116 // 对数据分段解密
117 try {
118 while (inputLen - offSet > 0) {
119 if (inputLen - offSet > maxBlock) {
120 cache = cipher.doFinal(data, offSet, maxBlock);
121 } else {
122 cache = cipher.doFinal(data, offSet, inputLen - offSet);
123 }
124 out.write(cache, 0, cache.length);
125 i++;
126 offSet = i * maxBlock;
127 }
128 byte[] bytes = out.toByteArray();
129 out.close();
130 return bytes;
131 } catch (Exception e) {
132 throw new RuntimeException("加解密阀值为["+maxBlock+"]的数据时发生异常", e);
133 }
134 }
135
136
137
138
139
140 public static void main(String[] args) throws Exception {
141 init();
142 String msg = "我是冬竹";
143 System.out.println("公钥加密-私钥解密：");
144 String mi = encryptByPublicKey(msg, getPublicKey(keyMap.get(PUBLIC_KEY)));
145 System.out.println("密文：" + mi);
146
147 String ming = decryptByPrivateKey(mi , getPrivateKey(keyMap.get(PRIVATE_KEY)));
148 System.out.println("明文：" + ming);
149
150 System.out.println("私钥加密-公钥解密：");
151 String mi2 = encryptByPrivate(msg, getPrivateKey(keyMap.get(PRIVATE_KEY)));
152 System.out.println("密文：" + mi2);
153
154 String ming2 = decrytByPublic(mi2 , getPublicKey(keyMap.get(PUBLIC_KEY)));
155 System.out.println("明文：" + ming);
156 }
157
158 }
这这这好长啊........
说一下这个过程:
1. keyPair.getPublic() 获得的字节数组 用encodeBase64URLSafeString() 编码成字符串，也就是我们有时候用的那种很多字母的那种公钥（私钥）
2. 用decodeBase64() 把公钥解码成字节数组，然后通过X509编码的Key指令获得公钥对象 RSAPublicKey
加密字符串的过程：
1. msg.getBytes() 获得字符数组， 然后用rsaSplitCode() 方法加密，再用encodeBase64URLSafeString编码成字符串（密文）
解密字符串的过程：
1. decodeBase64() 把密文解码成字符数组，再用new String（）方法转为字符串
然后我用的Base64类是commons-net-3.1.jar 里的，这个是我的maven仓库里(maven真的太方便了(●ˇ?ˇ●)）
放上这个：https://github.com/MoisAbby/XZUtils， 以后会把我攒的好用的东西都放上来
原文地址：https://www.cnblogs.com/MoisAbby/p/8443425.html
时间： 2024-08-12 09:55:53