RSA算法----加密解密

/** * RSA加密算法的演示验证 * RSA是一种分组加密算法 * 注意:密钥对采用的长度决定了加密块的长度，我这里取的是2048，即256byte * 由于加密块的长度固定为256，因此明文的长度至多为256 - 11 = 245byte * 我这里明文长度取的是128byte，密文长度为256byte，它适合于小文件加密 */ package encrypto; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.security.InvalidKeyException; import java.security.Key; import java.security.KeyFactory; import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.NoSuchAlgorithmException; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import java.security.spec.InvalidKeySpecException; import java.security.spec.PKCS8EncodedKeySpec; import java.security.spec.X509EncodedKeySpec; import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.NoSuchPaddingException; /** * @author liuhuabai,liuhuabai@163.com * */ public class RSADemo { /** * 公钥 */ private RSAPublicKey publicKey; /** * 私钥 */ private RSAPrivateKey privateKey; /** * 用于加解密 */ private Cipher cipher; /** * 明文块的长度 它必须小于密文块的长度 - 11 */ private int originLength = 128; /** * 密文块的长度 */ private int encrytLength = 256; /** * 得到初始化的公钥和私钥 * @throws NoSuchAlgorithmException * @throws NoSuchPaddingException */ public void initKey() throws NoSuchAlgorithmException, NoSuchPaddingException { //RSA加密算法：创建密钥对，长度采用2048 KeyPairGenerator kg = KeyPairGenerator.getInstance("RSA"); kg.initialize(encrytLength * 8); KeyPair keypair = kg.generateKeyPair(); //分别得到公钥和私钥 publicKey = (RSAPublicKey) keypair.getPublic(); privateKey = (RSAPrivateKey) keypair.getPrivate(); } /** * 将公钥保存至文件 * @param file 待写入的文件 * @return true 写入成功;false 写入失败 */ public boolean savePublicKey(File file) { return this.saveKey(publicKey, file); } /** * 将私钥保持至文件 * @param file 待写入的文件 * @return true 写入成功;false 写入失败 */ public boolean savePrivateKey(File file) { return this.saveKey(privateKey, file); } //将Key文件保持到文件中 private boolean saveKey(Key key,File file) { boolean write; FileOutputStream fos = null; try { fos = new FileOutputStream(file); ObjectOutputStream oos = new ObjectOutputStream(fos); //System.out.println(key.getFormat()); //公钥默认使用的是X.509编码，私钥默认采用的是PKCS #8编码 byte [] encode = key.getEncoded(); //注意，此处采用writeObject方法，读取时也要采用readObject方法 oos.writeObject(encode); write = true; } catch (IOException e) { write = false; } finally { try { if(fos != null) fos.close(); } catch (IOException e) { e.printStackTrace(); } } return write; } /** * 从文件中得到公钥 * @param file 保存公钥的文件 */ public void getPublicKey(File file) { getKey(file,0); } /** * 从文件中得到私钥 * @param file 保存私钥的文件 */ public void getPrivateKey(File file) { getKey(file,1); } private void getKey(File file,int mode) { FileInputStream fis; try { //读取数据 fis = new FileInputStream(file); ObjectInputStream ois = new ObjectInputStream(fis); byte [] keybyte = (byte[]) ois.readObject(); //关闭资源 ois.close(); //默认编码 KeyFactory keyfactory = KeyFactory.getInstance("RSA"); //得到公钥或是私钥 if(mode == 0) { X509EncodedKeySpec x509eks= new X509EncodedKeySpec(keybyte); publicKey = (RSAPublicKey) keyfactory.generatePublic(x509eks); //System.out.println(pk.getAlgorithm()); } else { PKCS8EncodedKeySpec pkcs8eks = new PKCS8EncodedKeySpec(keybyte); privateKey = (RSAPrivateKey) keyfactory.generatePrivate(pkcs8eks); //System.out.println(pk.getAlgorithm()); } } catch (IOException e) { e.printStackTrace(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (InvalidKeySpecException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } /** * 数据RSA加密 * @param origin 明文 * @return 密文 */ protected byte [] encrypt(byte [] origin) { //byte [] enc = new byte [encrytLength]; byte [] enc = null; try { cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.ENCRYPT_MODE, publicKey); enc = cipher.doFinal(origin); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (NoSuchPaddingException e) { e.printStackTrace(); } catch (InvalidKeyException e) { e.printStackTrace(); } catch (IllegalBlockSizeException e) { e.printStackTrace(); } catch (BadPaddingException e) { e.printStackTrace(); } return enc; } /** * 数据RSA解密 * @param enc 密文 * @return 明文 */ protected byte [] decrypt(byte [] enc) { //byte [] origin = new byte [originLength]; byte [] origin = null; try { cipher = Cipher.getInstance("RSA"); cipher.init(Cipher.DECRYPT_MODE, privateKey); origin = cipher.doFinal(enc); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (NoSuchPaddingException e) { e.printStackTrace(); } catch (InvalidKeyException e) { e.printStackTrace(); } catch (IllegalBlockSizeException e) { e.printStackTrace(); } catch (BadPaddingException e) { e.printStackTrace(); } return origin; } /** * 加密文件 * @param origin 明文件 * @throws IOException */ public void encryptFile(File origin) throws IOException { FileInputStream fis = null; FileOutputStream fos = null; //读入 fis = new FileInputStream(origin); BufferedInputStream bis = new BufferedInputStream(fis); byte [] originbyte = new byte [originLength]; //写出 fos = new FileOutputStream(new File(origin+".encrypt")); BufferedOutputStream bos = new BufferedOutputStream(fos); byte [] encryptbyte; //int k; while(bis.read(originbyte) > 0) { encryptbyte = this.encrypt(originbyte); bos.write(encryptbyte); originbyte = new byte[originLength]; } //压入 bos.flush(); //关闭资源 if(fis != null) fis.close(); if(fos != null) fos.close(); } /** * 解密文件 * @param encrypt 密文件 * @throws IOException */ public void decryptFile(File encrypt) throws IOException { FileInputStream fis = null; FileOutputStream fos = null; //读入 fis = new FileInputStream(encrypt); BufferedInputStream bis = new BufferedInputStream(fis); byte [] encryptbyte = new byte [encrytLength]; //写出 fos = new FileOutputStream(new File(encrypt+".decrypt")); BufferedOutputStream bos = new BufferedOutputStream(fos); byte [] originbyte; //int k; while(bis.read(encryptbyte) > 0) { originbyte = this.decrypt(encryptbyte); bos.write(originbyte); encryptbyte = new byte [encrytLength]; } //压入 bos.flush(); //关闭资源 if(fis != null) fis.close(); if(fos != null) fos.close(); } /** * @param args * @throws IOException */ public static void main(String[] args) throws Exception { RSADemo rsa = new RSADemo(); rsa.initKey(); rsa.encryptFile(new File("E:/hello.txt")); rsa.decryptFile(new File("E:/hello.txt.encrypt")); rsa.savePublicKey(new File("E:/public.key")); rsa.savePrivateKey(new File("E:/private.key")); //rsa.getPublicKey(new File("E:/public.key")); //rsa.getPrivateKey(new File("E:/private.key")); //rsa.encryptFile(new File("E:/hello.txt")); //rsa.decryptFile(new File("E:/hello.txt.encrypt")); } }