java对称加密和解密
/** * */package security;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.io.UnsupportedEncodingException;import java.math.BigInteger;import java.security.InvalidKeyException;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import java.security.spec.InvalidKeySpecException;import javax.crypto.BadPaddingException;import javax.crypto.Cipher;import javax.crypto.CipherInputStream;import javax.crypto.IllegalBlockSizeException;import javax.crypto.SecretKey;import javax.crypto.SecretKeyFactory;import javax.crypto.spec.DESKeySpec;/** * DESC: 对称加密 * <p> * 仅作学习交流用途，严禁用作商业用途。版权所有，伪版必究。 * * @Copyright YangFei * </p> * @author yfei Date:2013-8-28 */public class SymmetricEncryption {/** * mark as DES. */private static final String ALGORITHM = "DES";/** * DEFAULT password. */private static String defaultStrKey = "yangfei";/** * 加密器. */private Cipher decryptCipher = Cipher.getInstance(ALGORITHM);/** * 解密器. */private Cipher encryptCipher = Cipher.getInstance(ALGORITHM);/** * construct without parameter. * * @throws Exception * the exception */public SymmetricEncryption() throws Exception {// key = DEFAULT_KEY;this(defaultStrKey);}/** * construct with parameter password. * * @param strKey * the str key * @throws Exception * the exception */public SymmetricEncryption(String strKey) throws Exception {// DES算法要求有一个可信任的随机数源SecureRandom sr = new SecureRandom();// 生成DESKeySecretKey desKey = generateDESKey(strKey);// 初始化加密器encryptCipher.init(Cipher.ENCRYPT_MODE, desKey, sr);// 初始化解密器decryptCipher.init(Cipher.DECRYPT_MODE, desKey, sr);}/** * <b>解密二进制数据.</b> * * @param source * the source * @return the byte[] */public byte[] decrypt(byte[] source) {byte[] result = null;try {result = decryptCipher.doFinal(source);} catch (IllegalBlockSizeException e) {e.printStackTrace();} catch (BadPaddingException e) {e.printStackTrace();}return result;}/* * (non-Javadoc) * * @see com.cnpc.pms.base.crypto.ICrypto#decrypt(java.io.InputStream) *//** * Decrypt. * * @param input * the input * @return the output stream */public OutputStream decrypto(InputStream input,OutputStream output) {//OutputStream output = new ByteArrayOutputStream();CipherInputStream cis = new CipherInputStream(input, decryptCipher);byte[] buffer = new byte[1024];int r;try {while ((r = cis.read(buffer)) > 0) {output.write(buffer, 0, r);}cis.close();input.close();} catch (IOException e) {e.printStackTrace();}return output;}/** * <b>加密二进制数据.</b> * * @param source * the source * @return the byte[] */public byte[] encrypt(byte[] source) {byte[] result = null;try {result = encryptCipher.doFinal(source);} catch (IllegalBlockSizeException e) {e.printStackTrace();} catch (BadPaddingException e) {e.printStackTrace();}return result;}/** * Encrypt. * * @param input * the input * @return the output stream */public OutputStream encrypto(InputStream input,OutputStream output) {//OutputStream output = new ByteArrayOutputStream();CipherInputStream cis = new CipherInputStream(input, encryptCipher);byte[] buffer = new byte[1024];int r;try {while ((r = cis.read(buffer)) > 0) {output.write(buffer, 0, r);}cis.close();input.close();} catch (IOException e) {e.printStackTrace();}return output;}/** * <b>transfer byte[8] to SecretKey.</b> * * @param strKey * the str key * @return the secret key * @throws InvalidKeyException * the invalid key exception * @throws NoSuchAlgorithmException * the no such algorithm exception * @throws InvalidKeySpecException * the invalid key spec exception * @throws UnsupportedEncodingException */private final SecretKey generateDESKey(String strKey)throws InvalidKeyException, NoSuchAlgorithmException,InvalidKeySpecException, UnsupportedEncodingException {byte[] byteKey = this.getByteKey(strKey);BigInteger bigInteger = new BigInteger(1,byteKey);System.out.println("the secrity md5 key is == "+bigInteger.toString(16));// get DESKey.DESKeySpec dks = null;SecretKeyFactory keyFactory = null; // key FactorySecretKey secretKey = null; // DESKey// 从原始密匙数据创建DESKeySpec对象dks = new DESKeySpec(byteKey);// 创建一个密匙工厂，然后用它把DESKeySpec转换成一个SecretKey对象keyFactory = SecretKeyFactory.getInstance(ALGORITHM);secretKey = keyFactory.generateSecret(dks);return secretKey;}/** * <b>transfer password to byte[8]..</b> byte[] * * @param strKey * the str key * @return the byte key * @throws NoSuchAlgorithmException */private final byte[] getByteKey(final String strKey) throws NoSuchAlgorithmException {// transfer password to byte[8].MessageDigest md = MessageDigest.getInstance("MD5");return md.digest(strKey.getBytes());}/** * @param args * */public static void main(String[] args) {try {SymmetricEncryption clazz = new SymmetricEncryption();InputStream input = new FileInputStream(new File("testData/test.docx"));OutputStream out = new FileOutputStream(new File("testData/test_en.docx"));clazz.encrypto(input, out);input.close();out.close();InputStream input2 = new FileInputStream(new File("testData/test_en.docx"));OutputStream out2 = new FileOutputStream(new File("testData/test_de.docx"));clazz.decrypto(input2, out2);input2.close();out2.close();} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}对称算法：A用一个密钥对一个文件加密，而B读取这个文件的话，则须要和A一样的密钥，双方共享一个私钥（而在web环境下，私钥在传递时简单被侦听）：
运用私钥加密的话，最先须要一个密钥，可用javax.crypto.KeyGenerator产生一个密钥(java.security.Key), 然后传递给一个加密工具(javax.crypto.Cipher),该工具再运用相应的算法来执行 加密，首要对称算法有：DES（实际密钥只用到56 位），AES（支持三种密钥长度：128、192、256位），通常最先 128位，其他的还有DESede等，jdk1.5种也提供了对对称算法的支持，