RSA为非对称加密算法。
数字签名的过程：1、对明文数据进行HASH加密，不可逆；2、对加密后的数据再用RSA的私钥进行二次加密。
数字签名的验证过程：1、对明文数据进行HASH加密，不可逆；2、用RSA的公钥对数字签名后的数据进行解密；3、把1的结果和2的结果进行比较是否相等。
RSA加密的过程和解密的过程都需要三步：加/解密、分组、填充。这三部分每一步都可以选择各自的算法。例如：RSA/ECB/PKCS1Padding。
在这里RSA的公钥是用X509编码的。
在这里RSA的私钥使用PKCS8编码的。
1import java.security.Key; 2import java.security.KeyFactory; 3import java.security.KeyPair; 4import java.security.KeyPairGenerator; 5import java.security.PrivateKey; 6import java.security.PublicKey; 7import java.security.Signature; 8import java.security.spec.PKCS8EncodedKeySpec; 9import java.security.spec.X509EncodedKeySpec; 10import java.util.Base64; 11import java.util.HashMap; 12import java.util.Map; 13 14import javax.crypto.Cipher; 15 16public class Secret { 17 18 public static final String KEY_ALGORITHM = "RSA"; 19 public static final String SIGNATURE_ALGORITHM = "SHA256withRSA"; 20 private static final String PUBLIC_KEY = "PublicKey"; 21 private static final String PRIVATE_KEY = "PrivateKey"; 22 23 public static void main(String[] args) throws Exception{ 24 // TODO Auto-generated method stub 25 Map<String,Key> keyMap = initKeyPair(); 26 String publicKey = encryptBASE64(keyMap.get(PUBLIC_KEY).getEncoded()); 27 String privateKey = encryptBASE64(keyMap.get(PRIVATE_KEY).getEncoded()); 28 String data = "123456"; 29 byte[] miwen = encryptByPrivateKey(data.getBytes(), privateKey); 30 byte[] mingwen = decryptByPublicKey(miwen, publicKey); 31 String redata = new String(mingwen); 32 System.out.println(redata); 33 String data2 = "asdfgh"; 34 byte[] miwen2 = encryptByPublicKey(data2.getBytes(), publicKey); 35 byte[] mingwen2 = decryptByPrivateKey(miwen2, privateKey); 36 String redata2 = new String(mingwen2); 37 System.out.println(redata2); 38 String data3 = "678901"; 39 byte[] miwen3 = sign(data3.getBytes(), privateKey); 40 boolean flag = verify(data3.getBytes(), publicKey, miwen3); 41 System.out.println(flag); 42 43 44 } 45 //生成密匙对 46 public static Map<String,Key> initKeyPair() throws Exception{ 47 KeyPairGenerator kpg = KeyPairGenerator.getInstance(KEY_ALGORITHM); 48 kpg.initialize(1024); 49 KeyPair keyPair = kpg.generateKeyPair(); 50 PublicKey publicKey = keyPair.getPublic(); 51 PrivateKey privateKey = keyPair.getPrivate(); 52 Map<String,Key> keyMap = new HashMap<>(); 53 keyMap.put(PUBLIC_KEY, publicKey); 54 keyMap.put(PRIVATE_KEY, privateKey); 55 return keyMap; 56 } 57 //字节数组到公钥 58 public static PrivateKey strToPrivateKey(String str) throws Exception{ 59 PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(decryptBASE64(str)); 60 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM); 61 PrivateKey privateKey = keyFactory.generatePrivate(pkcs8KeySpec); 62 return privateKey; 63 } 64 //字节数组到私钥 65 public static PublicKey strToPublicKey(String str) throws Exception{ 66 X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(decryptBASE64(str)); 67 KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM); 68 PublicKey publicKey = keyFactory.generatePublic(x509KeySpec); 69 return publicKey; 70 } 71 //字节数组到文件字符串 72 public static String encryptBASE64(byte[] bytes) { 73 return Base64.getEncoder().encodeToString(bytes); 74 } 75 //文件字符串到字节数组 76 public static byte[] decryptBASE64(String str) { 77 return Base64.getDecoder().decode(str); 78 } 79 //用公钥加密 80 public static byte[] encryptByPublicKey(byte[] data, String key) throws Exception{ 81 PublicKey publicKey = strToPublicKey(key); 82 Cipher cipher = Cipher.getInstance(KEY_ALGORITHM); 83 //Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 84 //加解密算法/分組算法/填充算法 85 cipher.init(Cipher.ENCRYPT_MODE, publicKey); 86 return cipher.doFinal(data); 87 } 88 //用私钥加密 89 public static byte[] encryptByPrivateKey(byte[] data, String key) throws Exception{ 90 PrivateKey privateKey = strToPrivateKey(key); 91 Cipher cipher = Cipher.getInstance(KEY_ALGORITHM); 92 //Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 93 //加解密算法/分組算法/填充算法 94 cipher.init(Cipher.ENCRYPT_MODE, privateKey); 95 return cipher.doFinal(data); 96 } 97 //用公钥解密 98 public static byte[] decryptByPublicKey(byte[] data, String key) throws Exception { 99 PublicKey publicKey = strToPublicKey(key); 100 Cipher cipher = Cipher.getInstance(KEY_ALGORITHM); 101 //Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 102 //加解密算法/分組算法/填充算法 103 cipher.init(Cipher.DECRYPT_MODE, publicKey); 104 return cipher.doFinal(data); 105 } 106 //用私钥解密 107 public static byte[] decryptByPrivateKey(byte[] data, String key) throws Exception { 108 PrivateKey privateKey = strToPrivateKey(key); 109 Cipher cipher = Cipher.getInstance(KEY_ALGORITHM); 110 //Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding"); 111 //加解密算法/分組算法/填充算法 112 cipher.init(Cipher.DECRYPT_MODE, privateKey); 113 return cipher.doFinal(data); 114 } 115 //对字符串进行数字签名 116 public static byte[] sign(byte[] data, String privateKey) throws Exception { 117 PrivateKey priKey = strToPrivateKey(privateKey); 118 Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM); 119 signature.initSign(priKey); 120 signature.update(data); 121 return signature.sign(); 122 } 123 //对数字签名进行验证 124 public static boolean verify(byte[] data, String publicKey, byte[] sign) throws Exception { 125 PublicKey pubKey = strToPublicKey(publicKey); 126 Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM); 127 signature.initVerify(pubKey); 128 signature.update(data); 129 return signature.verify(sign); 130 } 131}