首先RSA是一个非对称的加密算法。所以在使用该算法加密解密之前,必须先行生成密钥对。包含公钥和私钥
JDK中提供了生成密钥对的类KeyPairGenerator,实比例如以下:
public static Map<String, Object> genKeyPair() throws Exception { // 获取公钥私钥密钥对的生成器 KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA"); // 初始化确定密钥大小的密钥生成器 kpg.initialize(1024); // 生成密钥对 KeyPair kp = kpg.generateKeyPair(); RSAPublicKey publicKey = (RSAPublicKey) kp.getPublic(); RSAPrivateKey privateKey = (RSAPrivateKey) kp.getPrivate(); Map<String, Object> keyMap = new HashMap<String, Object>(); keyMap.put(PUBLIC_KEY, publicKey); keyMap.put(PRIVATE_KEY, privateKey); return keyMap; }以上这段代码返回的是一个Map类型的数据。当中存储了公钥和私钥
当你完毕了密钥对的生成之后,你就能够将公钥公开出去了。让相关的加密程序通过该公钥对实施RSA加密
public static byte[] encryptByPublicKey(byte[] data, String publicKey) throws Exception { //data即是待加密的数据String.getBytes就可以 byte[] keyBytes = Base64Utils.decode(publicKey); //依据指定的编码密钥创建一个新的X509EncodedKeySpec X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes); KeyFactory keyFactory = KeyFactory.getInstance(ENCRYPT_ALGORITHM); //依据提供的密钥规范生成公钥对象 Key publicK = keyFactory.generatePublic(x509KeySpec); // 对数据加密 Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm()); //用密钥初始化加密模式的cipher。全部后面的doFinal方法做的是加密 cipher.init(Cipher.ENCRYPT_MODE, publicK); int inputLen = data.length; ByteArrayOutputStream out = new ByteArrayOutputStream(); int offSet = 0; byte[] cache; int i = 0; // 对数据分段加密 while (inputLen - offSet > 0) { if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {//一次加密的字节长度 cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK); } else { cache = cipher.doFinal(data, offSet, inputLen - offSet); } out.write(cache, 0, cache.length); i++; offSet = i * MAX_ENCRYPT_BLOCK; } byte[] encryptedData = out.toByteArray(); out.close(); return encryptedData; }
加密完毕之后通过自己的私钥对密文进行解密
public static byte[] decryptByPrivateKey(byte[] data, String privateKey) throws Exception { byte[] keyBytes = Base64Utils.decode(privateKey); PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes); KeyFactory keyFactory = KeyFactory.getInstance(ENCRYPT_ALGORITHM); Key privateK = keyFactory.generatePrivate(pkcs8KeySpec); Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm()); cipher.init(Cipher.DECRYPT_MODE, privateK); int inputLen = data.length; ByteArrayOutputStream out = new ByteArrayOutputStream(); 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(data, offSet, MAX_DECRYPT_BLOCK); } else { cache = cipher.doFinal(data, offSet, inputLen - offSet); } out.write(cache, 0, cache.length); i++; offSet = i * MAX_DECRYPT_BLOCK; } byte[] decryptedData = out.toByteArray(); out.close(); return decryptedData; }生成密钥对:
try { Map<String, Object> keyMap = RSAUtils.genKeyPair(); publicKey = RSAUtils.getPublicKey(keyMap); privateKey = RSAUtils.getPrivateKey(keyMap); System.out.println("公钥-->" + publicKey); System.out.println("私钥-->" + privateKey); } catch (Exception e) { e.printStackTrace(); }
执行结果展示:
公钥-->MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCjJOdVRlDN/5nWHmpFtc9XffgmT2SAj7b+yBk55HSr1iQQt5k8/4O5qdnk3qxhgIgWuSyDpxR2FK5dzfXsomjc0L2CZGaStAkbbvw1wbOSYo11cxNpkphn3PIVbuBxrpEuCJ4HrMKTuBk662aA0ysxy2/BrK4NXxtRlMxI+/BYsQIDAQAB
私钥-->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
利用公钥加密。私钥解密:
System.out.println("公钥加密——私钥解密"); System.out.println("加密前数据的内容是-->" + sourceStr); byte[] data = sourceStr.getBytes(); byte[] encryptData = RSAUtils.encryptByPublicKey(data, publicKey); System.out.println("加密后的数据内容是-->" + new String(encryptData)); byte[] decryptData = RSAUtils.decryptByPrivateKey(encryptData, privateKey); System.out.println("解密后的数据内容是-->" + new String(decryptData));
公钥加密——私钥解密
加密前数据的内容是-->这是一段待加密的数据
加密后的数据内容是-->(���%5 [�͖W��uA- ��m�u�&w�2��gQ���-5�Q���`7:Й�C,�8t�qM�gJ��e2"�)y��͓����� �Y��@�y*_�M�����x*;�f1���v֚�@�h�}P?X�2
解密后的数据内容是-->这是一段待加密的数据
附Base64Utils.java
package rsa; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.OutputStream; public class Base64Utils { private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray(); /** * data[]进行编码 * * @param data * @return */ public static String encode(byte[] data) { int start = 0; int len = data.length; StringBuffer buf = new StringBuffer(data.length * 3 / 2); int end = len - 3; int i = start; int n = 0; while (i <= end) { int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8) | (((int) data[i + 2]) & 0x0ff); buf.append(legalChars[(d >> 18) & 63]); buf.append(legalChars[(d >> 12) & 63]); buf.append(legalChars[(d >> 6) & 63]); buf.append(legalChars[d & 63]); i += 3; if (n++ >= 14) { n = 0; buf.append(" "); } } if (i == start + len - 2) { int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8); buf.append(legalChars[(d >> 18) & 63]); buf.append(legalChars[(d >> 12) & 63]); buf.append(legalChars[(d >> 6) & 63]); buf.append("="); } else if (i == start + len - 1) { int d = (((int) data[i]) & 0x0ff) << 16; buf.append(legalChars[(d >> 18) & 63]); buf.append(legalChars[(d >> 12) & 63]); buf.append("=="); } return buf.toString(); } private static int decode(char c) { if (c >= 'A' && c <= 'Z') return ((int) c) - 65; else if (c >= 'a' && c <= 'z') return ((int) c) - 97 + 26; else if (c >= '0' && c <= '9') return ((int) c) - 48 + 26 + 26; else switch (c) { case '+': return 62; case '/': return 63; case '=': return 0; default: throw new RuntimeException("unexpected code: " + c); } } /** * Decodes the given Base64 encoded String to a new byte array. The byte array holding the decoded data is returned. */ public static byte[] decode(String s) { ByteArrayOutputStream bos = new ByteArrayOutputStream(); try { decode(s, bos); } catch (IOException e) { throw new RuntimeException(); } byte[] decodedBytes = bos.toByteArray(); try { bos.close(); bos = null; } catch (IOException ex) { System.err.println("Error while decoding BASE64: " + ex.toString()); } return decodedBytes; } private static void decode(String s, OutputStream os) throws IOException { int i = 0; int len = s.length(); while (true) { while (i < len && s.charAt(i) <= ' ') i++; if (i == len) break; int tri = (decode(s.charAt(i)) << 18) + (decode(s.charAt(i + 1)) << 12) + (decode(s.charAt(i + 2)) << 6) + (decode(s.charAt(i + 3))); os.write((tri >> 16) & 255); if (s.charAt(i + 2) == '=') break; os.write((tri >> 8) & 255); if (s.charAt(i + 3) == '=') break; os.write(tri & 255); i += 4; } } /** * data[]进行编码 * * @param data * @return */ public static String Base64Encoder(byte[] data) { int start = 0; int len = data.length; StringBuffer buf = new StringBuffer(data.length * 3 / 2); int end = len - 3; int i = start; int n = 0; while (i <= end) { int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 0x0ff) << 8) | (((int) data[i + 2]) & 0x0ff); buf.append(legalChars[(d >> 18) & 63]); buf.append(legalChars[(d >> 12) & 63]); buf.append(legalChars[(d >> 6) & 63]); buf.append(legalChars[d & 63]); i += 3; if (n++ >= 14) { //不须要空格 n = 0; } } if (i == start + len - 2) { int d = ((((int) data[i]) & 0x0ff) << 16) | ((((int) data[i + 1]) & 255) << 8); buf.append(legalChars[(d >> 18) & 63]); buf.append(legalChars[(d >> 12) & 63]); buf.append(legalChars[(d >> 6) & 63]); buf.append("="); } else if (i == start + len - 1) { int d = (((int) data[i]) & 0x0ff) << 16; buf.append(legalChars[(d >> 18) & 63]); buf.append(legalChars[(d >> 12) & 63]); buf.append("=="); } return buf.toString(); } }