一、公钥加密和私钥解密
/**RSA算法*/ public static final String RSA = "RSA"; /**加密方式，android的*/ // public static final String TRANSFORMATION = "RSA/None/NoPadding"; /**加密方式，标准jdk的*/ public static final String TRANSFORMATION = "RSA/None/PKCS1Padding"; /** 使用公钥加密 */ public static byte[] encryptByPublicKey(byte[] data, byte[] publicKey) throws Exception { // 得到公钥对象 X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKey); KeyFactory keyFactory = KeyFactory.getInstance("RSA"); PublicKey pubKey = keyFactory.generatePublic(keySpec); // 加密数据 Cipher cp = Cipher.getInstance(TRANSFORMATION); cp.init(Cipher.ENCRYPT_MODE, pubKey); return cp.doFinal(data); } /** 使用私钥解密 */ public static byte[] decryptByPrivateKey(byte[] encrypted, byte[] privateKey) throws Exception { // 得到私钥对象 PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKey); KeyFactory kf = KeyFactory.getInstance(RSA); PrivateKey keyPrivate = kf.generatePrivate(keySpec); // 解密数据 Cipher cp = Cipher.getInstance(TRANSFORMATION); cp.init(Cipher.DECRYPT_MODE, keyPrivate); byte[] arr = cp.doFinal(encrypted); return arr; }
1.data是要加密的数据，如果是字符串则getBytes。publicKey是公钥，privateKey是私钥。自定义密钥对测试
String data = "hello world"; try { int keyLength = 1024; //生成密钥对 KeyPair keyPair = RSAUtils.generateRSAKeyPair(keyLength); //获取公钥 byte[] publicKey = RSAUtils.getPublicKey(keyPair); //获取私钥 byte[] privateKey = RSAUtils.getPrivateKey(keyPair); //用公钥加密 byte[] encrypt = RSAUtils.encryptByPublicKey(data.getBytes(), publicKey); Log.d("TAG", "加密后的数据：" + StringUtils.byteArrayToString(encrypt)); //用私钥解密 byte[] decrypt = RSAUtils.decryptByPrivateKey(encrypt, privateKey); Log.d("TAG", "解密后的数据：" + new String(decrypt, "utf-8")); } catch (Exception e) { e.printStackTrace(); }
2.从文件中读取公钥
String data = "hello world"; //读取公钥文件 String publicKeyString = IOUtils.readAssetsFile(this, "rsa_public_key.pem"); //base64解码 byte[] publicKey = Base64Utils.decodeToBytes(publicKeyString); try { //加密 byte[] encrypt = RSAUtils.encryptByPublicKey(data.getBytes(), publicKey); Log.d("TAG", "加密后的数据：" + StringUtils.byteArrayToString(encrypt)); // //读取私钥文件 // String privateKeyString = IOUtils.readAssetsFile(this, "rsa_private_key.pem"); // //base64解码 // byte[] privateKey = Base64Utils.decodeToBytes(privateKeyString); // //解密 // byte[] decrypt = RSAUtils.decryptByPrivateKey(encrypt, privateKey); // Log.d("TAG", "解密后的数据：" + new String(decrypt, "utf-8")); } catch (Exception e) { e.printStackTrace(); }
二、公钥分段加密和私钥分段解密
当加密的数据过长时，会出现javax.crypto.IllegalBlockSizeException: Data must not be longer than 117 bytes的异常。rsa算法规定一次加密的数据不能超过生成密钥对时的keyLength/8-11，keyLength一般是1024个字节，则加密的数据不能超过117个字节
/**秘钥默认长度*/ public static final int DEFAULT_KEY_SIZE = 1024; /**加密的数据最大的字节数，即117个字节*/ public static final int DEFAULT_BUFFERSIZE = (DEFAULT_KEY_SIZE / 8) - 11; /**当加密的数据超过DEFAULT_BUFFERSIZE，则使用分段加密*/ public static final byte[] DEFAULT_SPLIT = "#PART#".getBytes(); /** 使用公钥分段加密 */ public static byte[] encryptByPublicKeyForSpilt(byte[] data, byte[] publicKey) throws Exception{ int dataLen = data.length; if (dataLen <= DEFAULT_BUFFERSIZE) { return encryptByPublicKey(data, publicKey); } List<Byte> allBytes = new ArrayList<Byte>(2048); int bufIndex = 0; int subDataLoop = 0; byte[] buf = new byte[DEFAULT_BUFFERSIZE]; for (int i = 0; i < dataLen; i++) { buf[bufIndex] = data[i]; if (++bufIndex == DEFAULT_BUFFERSIZE || i == dataLen - 1) { subDataLoop++; if (subDataLoop != 1) { for (byte b : DEFAULT_SPLIT) { allBytes.add(b); } } byte[] encryptBytes = encryptByPublicKey(buf, publicKey); for (byte b : encryptBytes) { allBytes.add(b); } bufIndex = 0; if (i == dataLen - 1) { buf = null; } else { buf = new byte[Math .min(DEFAULT_BUFFERSIZE, dataLen - i - 1)]; } } } byte[] bytes = new byte[allBytes.size()]; int i = 0; for (Byte b : allBytes) { bytes[i++] = b.byteValue(); } return bytes; } /** 使用私钥分段解密 */ public static byte[] decryptByPrivateKeyForSpilt(byte[] encrypted, byte[] privateKey) throws Exception { int splitLen = DEFAULT_SPLIT.length; if (splitLen <= 0) { return decryptByPrivateKey(encrypted, privateKey); } int dataLen = encrypted.length; List<Byte> allBytes = new ArrayList<Byte>(1024); int latestStartIndex = 0; for (int i = 0; i < dataLen; i++) { byte bt = encrypted[i]; boolean isMatchSplit = false; if (i == dataLen - 1) { // 到data的最后了 byte[] part = new byte[dataLen - latestStartIndex]; System.arraycopy(encrypted, latestStartIndex, part, 0, part.length); byte[] decryptPart = decryptByPrivateKey(part, privateKey); for (byte b : decryptPart) { allBytes.add(b); } latestStartIndex = i + splitLen; i = latestStartIndex - 1; } else if (bt == DEFAULT_SPLIT[0]) { // 这个是以split[0]开头 if (splitLen > 1) { if (i + splitLen < dataLen) { // 没有超出data的范围 for (int j = 1; j < splitLen; j++) { if (DEFAULT_SPLIT[j] != encrypted[i + j]) { break; } if (j == splitLen - 1) { // 验证到split的最后一位，都没有break，则表明已经确认是split段 isMatchSplit = true; } } } } else { // split只有一位，则已经匹配了 isMatchSplit = true; } } if (isMatchSplit) { byte[] part = new byte[i - latestStartIndex]; System.arraycopy(encrypted, latestStartIndex, part, 0, part.length); byte[] decryptPart = decryptByPrivateKey(part, privateKey); for (byte b : decryptPart) { allBytes.add(b); } latestStartIndex = i + splitLen; i = latestStartIndex - 1; } } byte[] bytes = new byte[allBytes.size()]; int i = 0; for (Byte b : allBytes) { bytes[i++] = b.byteValue(); } return bytes; }
测试分段加密和解密
String data = "hello world hello world hello world hello world hello world hello world hello world hello world " + "hello world hello world hello world hello world hello world hello world hello world hello world hello world " + "hello world hello world hello world hello world hello world hello world hello world hello world hello world "; Log.d("TAG", "要加密的数据：" + data + ", 要加密的数据长度：" + data.length()); try { //分段加密 byte[] encrypt = RSAUtils.encryptByPublicKeyForSpilt(data.getBytes(), publicKey); Log.d("TAG", "加密后的数据：" + StringUtils.byteArrayToString(encrypt)); //分段解密 byte[] decrypt = RSAUtils.decryptByPrivateKeyForSpilt(encrypt, privateKey); Log.d("TAG", "解密后的数据：" + new String(decrypt, "utf-8")); } catch (Exception e) { e.printStackTrace(); }
三、生成密钥对
/** 生成密钥对，即公钥和私钥。key长度是512-2048，一般为1024 */ public static KeyPair generateRSAKeyPair(int keyLength) throws NoSuchAlgorithmException { KeyPairGenerator kpg = KeyPairGenerator.getInstance(RSA); kpg.initialize(keyLength); return kpg.genKeyPair(); } /** 获取公钥，打印为48-12613448136942-12272-122-913111503-126115048-12...等等一长串用-拼接的数字 */ public static byte[] getPublicKey(KeyPair keyPair) { RSAPublicKey rsaPublicKey = (RSAPublicKey) keyPair.getPublic(); return rsaPublicKey.getEncoded(); } /** 获取私钥，同上 */ public static byte[] getPrivateKey(KeyPair keyPair) { RSAPrivateKey rsaPrivateKey = (RSAPrivateKey) keyPair.getPrivate(); return rsaPrivateKey.getEncoded(); }
生成公钥和私钥后，用base64编码
int keyLength = 1024; try { //生成密钥对 KeyPair keyPair = RSAUtils.generateRSAKeyPair(keyLength); //获取公钥 byte[] publicKey = RSAUtils.getPublicKey(keyPair); Log.d("TAG", "公钥：" + StringUtils.byteArrayToString(publicKey)); //公钥用base64编码 String encodePublic = Base64Utils.encodeToString(publicKey); Log.d("TAG", "base64编码的公钥：" + encodePublic); //获取私钥 byte[] privateKey = RSAUtils.getPrivateKey(keyPair); Log.d("TAG", "私钥：" + StringUtils.byteArrayToString(privateKey)); //私钥用base64编码 String encodePrivate = Base64Utils.encodeToString(privateKey); Log.d("TAG", "base64编码的私钥：" + encodePrivate); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); }
其它
一、android加密的数据服务器上无法解密？
android的rsa加密方式是RSA/ECB/NoPadding，而标准jdk是RSA/ECB/PKCS1Padding，所以加密时要设置标准jdk的加密方式
二、base64编码。因为不同的设备对字符的处理方式不同，字符有可能处理出错，不利于传输。所以先把数据做base64编码，变成可见字符，减少出错
官方提供的base64类，Base64.encode编码，Base64.decode解码。用这个会有换行符，需要自定义
三、rsa是非对称加密算法。依赖于大数计算，加密速度比des慢，通常只用于加密少量数据或密钥
四、公钥加密比私钥加密块，公钥解密比私钥解密慢。加密后的数据大概是加密前的1.5倍
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。