RSA?
??? 這種算法1978年就出現了，它是第一個既能用于數據加密也能用于數字簽名的算法。它易于理解和操作，也很流行。算法的名字以發明者的名字命名：Ron Rivest, AdiShamir 和Leonard Adleman。?
??? 這種加密算法的特點主要是密鑰的變化，上文我們看到DES只有一個密鑰。相當于只有一把鑰匙，如果這把鑰匙丟了，數據也就不安全了。RSA同時有兩把鑰匙，公鑰與私鑰。同時支持數字簽名。數字簽名的意義在于，對傳輸過來的數據進行校驗。確保數據在傳輸工程中不被修改。?

流程分析：?

甲方構建密鑰對兒，將公鑰公布給乙方，將私鑰保留。

甲方使用私鑰加密數據，然后用私鑰對加密后的數據簽名，發送給乙方簽名以及加密后的數據；乙方使用公鑰、簽名來驗證待解密數據是否有效，如果有效使用公鑰對數據解密。

乙方使用公鑰加密數據，向甲方發送經過加密后的數據；甲方獲得加密數據，通過私鑰解密。

按如上步驟給出序列圖，如下：?

通過java代碼實現如下：Coder類見?Java加密技術（一）?

import java.security.Key; import java.security.KeyFactory; import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.PrivateKey; import java.security.PublicKey; import java.security.Signature; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import java.security.spec.PKCS8EncodedKeySpec; import java.security.spec.X509EncodedKeySpec;import java.util.HashMap; import java.util.Map;import javax.crypto.Cipher;/*** RSA安全編碼組件* * @author 梁棟* @version 1.0* @since 1.0*/ public abstract class RSACoder extends Coder {public static final String KEY_ALGORITHM = "RSA";public static final String SIGNATURE_ALGORITHM = "MD5withRSA";private static final String PUBLIC_KEY = "RSAPublicKey";private static final String PRIVATE_KEY = "RSAPrivateKey";/*** 用私鑰對信息生成數字簽名* * @param data* 加密數據* @param privateKey* 私鑰* * @return* @throws Exception*/public static String sign(byte[] data, String privateKey) throws Exception {// 解密由base64編碼的私鑰byte[] keyBytes = decryptBASE64(privateKey);// 構造PKCS8EncodedKeySpec對象PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);// KEY_ALGORITHM 指定的加密算法KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);// 取私鑰匙對象PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);// 用私鑰對信息生成數字簽名Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);signature.initSign(priKey);signature.update(data);return encryptBASE64(signature.sign());}/*** 校驗數字簽名* * @param data* 加密數據* @param publicKey* 公鑰* @param sign* 數字簽名* * @return 校驗成功返回true 失敗返回false* @throws Exception* */public static boolean verify(byte[] data, String publicKey, String sign)throws Exception {// 解密由base64編碼的公鑰byte[] keyBytes = decryptBASE64(publicKey);// 構造X509EncodedKeySpec對象X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);// KEY_ALGORITHM 指定的加密算法KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);// 取公鑰匙對象PublicKey pubKey = keyFactory.generatePublic(keySpec);Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);signature.initVerify(pubKey);signature.update(data);// 驗證簽名是否正常return signature.verify(decryptBASE64(sign));}/*** 解密<br>* 用私鑰解密* * @param data* @param key* @return* @throws Exception*/public static byte[] decryptByPrivateKey(byte[] data, String key)throws Exception {// 對密鑰解密byte[] keyBytes = decryptBASE64(key);// 取得私鑰PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);// 對數據解密Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.DECRYPT_MODE, privateKey);return cipher.doFinal(data);}/*** 解密<br>* 用公鑰解密* * @param data* @param key* @return* @throws Exception*/public static byte[] decryptByPublicKey(byte[] data, String key)throws Exception {// 對密鑰解密byte[] keyBytes = decryptBASE64(key);// 取得公鑰X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key publicKey = keyFactory.generatePublic(x509KeySpec);// 對數據解密Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.DECRYPT_MODE, publicKey);return cipher.doFinal(data);}/*** 加密<br>* 用公鑰加密* * @param data* @param key* @return* @throws Exception*/public static byte[] encryptByPublicKey(byte[] data, String key)throws Exception {// 對公鑰解密byte[] keyBytes = decryptBASE64(key);// 取得公鑰X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key publicKey = keyFactory.generatePublic(x509KeySpec);// 對數據加密Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.ENCRYPT_MODE, publicKey);return cipher.doFinal(data);}/*** 加密<br>* 用私鑰加密* * @param data* @param key* @return* @throws Exception*/public static byte[] encryptByPrivateKey(byte[] data, String key)throws Exception {// 對密鑰解密byte[] keyBytes = decryptBASE64(key);// 取得私鑰PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);// 對數據加密Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());cipher.init(Cipher.ENCRYPT_MODE, privateKey);return cipher.doFinal(data);}/*** 取得私鑰* * @param keyMap* @return* @throws Exception*/public static String getPrivateKey(Map<String, Object> keyMap)throws Exception {Key key = (Key) keyMap.get(PRIVATE_KEY);return encryptBASE64(key.getEncoded());}/*** 取得公鑰* * @param keyMap* @return* @throws Exception*/public static String getPublicKey(Map<String, Object> keyMap)throws Exception {Key key = (Key) keyMap.get(PUBLIC_KEY);return encryptBASE64(key.getEncoded());}/*** 初始化密鑰* * @return* @throws Exception*/public static Map<String, Object> initKey() throws Exception {KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);keyPairGen.initialize(1024);KeyPair keyPair = keyPairGen.generateKeyPair();// 公鑰RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();// 私鑰RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();Map<String, Object> keyMap = new HashMap<String, Object>(2);keyMap.put(PUBLIC_KEY, publicKey);keyMap.put(PRIVATE_KEY, privateKey);return keyMap;} }

再給出一個測試類：?

import static org.junit.Assert.*;import org.junit.Before; import org.junit.Test;import java.util.Map;/*** * @author 梁棟* @version 1.0* @since 1.0*/ public class RSACoderTest {private String publicKey;private String privateKey;@Beforepublic void setUp() throws Exception {Map<String, Object> keyMap = RSACoder.initKey();publicKey = RSACoder.getPublicKey(keyMap);privateKey = RSACoder.getPrivateKey(keyMap);System.err.println("公鑰: \n\r" + publicKey);System.err.println("私鑰： \n\r" + privateKey);}@Testpublic void test() throws Exception {System.err.println("公鑰加密——私鑰解密");String inputStr = "abc";byte[] data = inputStr.getBytes();byte[] encodedData = RSACoder.encryptByPublicKey(data, publicKey);byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData,privateKey);String outputStr = new String(decodedData);System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);assertEquals(inputStr, outputStr);}@Testpublic void testSign() throws Exception {System.err.println("私鑰加密——公鑰解密");String inputStr = "sign";byte[] data = inputStr.getBytes();byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);byte[] decodedData = RSACoder.decryptByPublicKey(encodedData, publicKey);String outputStr = new String(decodedData);System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);assertEquals(inputStr, outputStr);System.err.println("私鑰簽名——公鑰驗證簽名");// 產生簽名String sign = RSACoder.sign(encodedData, privateKey);System.err.println("簽名:\r" + sign);// 驗證簽名boolean status = RSACoder.verify(encodedData, publicKey, sign);System.err.println("狀態:\r" + status);assertTrue(status);}}

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原文地址：http://snowolf.iteye.com/blog/381767

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轉載于:https://www.cnblogs.com/davidwang456/p/3925444.html

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