java rsa私钥加密是一种加密算法。私钥加密算法是用私钥来进行加密与解密信息。私钥加密也被称作对称加密，原因是加密与解密使用的秘钥是同一个。
RSA加密需要注意的事项如下：
1. 首先产生公钥与私钥
2. 设计加密与解密的算法
3. 私钥加密的数据信息只能由公钥可以解密
4. 公钥加密的数据信息只能由私钥可以解密
实战演练，具体步骤如下： public class RsaCryptTools { private static final String CHARSET = "utf-8" private static final Base64.Decoder decoder64 = Base64.getDecoder() private static final Base64.Encoder encoder64 = Base64.getEncoder() /** * 生成公私钥 * @param keySize * @return * @throws NoSuchAlgorithmException */ public static SecretKey generateSecretKey(int keySize) throws NoSuchAlgorithmException { //生成密钥对 KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA") keyGen.initialize(keySize, new SecureRandom()) KeyPair pair = keyGen.generateKeyPair() PrivateKey privateKey = pair.getPrivate() PublicKey publicKey = pair.getPublic() //这里可以将密钥对保存到本地 return new SecretKey(encoder64.encodeToString(publicKey.getEncoded()), encoder64.encodeToString(privateKey.getEncoded())) } /** * 私钥加密 * @param data * @param privateInfoStr * @return * @throws IOException * @throws InvalidCipherTextException */ public static String encryptData(String data, String privateInfoStr) throws IOException, InvalidKeySpecException, NoSuchAlgorithmException, InvalidKeyException, NoSuchPaddingException, BadPaddingException, IllegalBlockSizeException { Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding") cipher.init(Cipher.ENCRYPT_MODE, getPrivateKey(privateInfoStr)) return encoder64.encodeToString(cipher.doFinal(data.getBytes(CHARSET))) } /** * 公钥解密 * @param data * @param publicInfoStr * @return */ public static String decryptData(String data, String publicInfoStr) throws NoSuchPaddingException, NoSuchAlgorithmException, InvalidKeySpecException, InvalidKeyException, BadPaddingException, IllegalBlockSizeException, UnsupportedEncodingException { byte[] encryptDataBytes=decoder64.decode(data.getBytes(CHARSET)) //解密 Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding") cipher.init(Cipher.DECRYPT_MODE, getPublicKey(publicInfoStr)) return new String(cipher.doFinal(encryptDataBytes), CHARSET) } private static PublicKey getPublicKey(String base64PublicKey) throws NoSuchAlgorithmException, InvalidKeySpecException { X509EncodedKeySpec keySpec = new X509EncodedKeySpec(Base64.getDecoder().decode(base64PublicKey.getBytes())) KeyFactory keyFactory = KeyFactory.getInstance("RSA") return keyFactory.generatePublic(keySpec) } private static PrivateKey getPrivateKey(String base64PrivateKey) throws NoSuchAlgorithmException, InvalidKeySpecException { PrivateKey privateKey = null PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(Base64.getDecoder().decode(base64PrivateKey.getBytes())) KeyFactory keyFactory = null keyFactory = KeyFactory.getInstance("RSA") privateKey = keyFactory.generatePrivate(keySpec) return privateKey } /** * 密钥实体 * @author hank * @since 2020/2/28 0028 下午 16:27 */ public static class SecretKey { /** * 公钥 */ private String publicKey /** * 私钥 */ private String privateKey public SecretKey(String publicKey, String privateKey) { this.publicKey = publicKey this.privateKey = privateKey } public String getPublicKey() { return publicKey } public void setPublicKey(String publicKey) { this.publicKey = publicKey } public String getPrivateKey() { return privateKey } public void setPrivateKey(String privateKey) { this.privateKey = privateKey } @Override public String toString() { return "SecretKey{" + "publicKey='" + publicKey + '\'' + ", privateKey='" + privateKey + '\'' + '}' } } private static void writeToFile(String path, byte[] key) throws IOException { File f = new File(path) f.getParentFile().mkdirs() try(FileOutputStream fos = new FileOutputStream(f)) { fos.write(key) fos.flush() } } public static void main(String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException, IOException, BadPaddingException, IllegalBlockSizeException, InvalidKeyException, InvalidKeySpecException { SecretKey secretKey = generateSecretKey(2048) System.out.println(secretKey) String enStr = encryptData("你好测试测试", secretKey.getPrivateKey()) System.out.println(enStr) String deStr = decryptData(enStr, secretKey.getPublicKey()) System.out.println(deStr) enStr = encryptData("你好测试测试hello", secretKey.getPrivateKey()) System.out.println(enStr) deStr = decryptData(enStr, secretKey.getPublicKey()) System.out.println(deStr) } }
密钥是一组字符，比如"QWE12312SDA"。只有获得密钥才能进行加解密，比如我希望只有你才能解密我的加密的密文，那么我把密钥告诉你，就算其他人获取了密文和解密算法，也只有你才能解密。
3DES算法是指使用双长度（16字节）密钥K=（KL||KR）将8字节明文数据块进行3次DES加密/解密。如下所示： Y = DES(KL)[DES-1(KR)[DES(KL[X])]] 解密方式为： X = DES-1 (KL)[DES (KR)[ DES-1 (KL[Y])]] 其中，DES(KL[X])表示用密钥K对数据X进行DES加密，DES-1 (KL[Y])表示用密钥K对数据Y进行解密。 SessionKey的计算采用3DES算法，计算出单倍长度的密钥。表示法为:SK = Session(DK，DATA) 3DES加密算法为： VOID 3DES(BYTE DoubleKeyStr[16]， BYTE Data[8]， BYTE Out[8]) { BYTE Buf1[8]， Buf2[8]DES (&DoubleKeyStr[0]， Data， Buf1)UDES(&DoubleKeyStr[8]， Buf1， Buf2)DES (&DoubleKeyStr[0]， Buf2， Out)}
