获取摘要、加密、解密

生成SHA或MD5摘要

	MessageDigest sha = MessageDigest.getInstance("SHA");//字符串参数可以为："SHA"或"MD5"
		sha.update("luoxun".getBytes());
		byte[] digest = sha.digest();
		StringBuilder sb = new StringBuilder();
		for(int i= 0;i<digest.length;i++){
			int v = digest[i]&0XFF;
			if(v<16) sb.append("0");
			sb.append(Integer.toString(v,16)).append(" ");
		}
		print(sb.toString().toUpperCase());

AES加密解密文件demo

	
//生成密钥
private static SecretKey generatorKey() throws NoSuchAlgorithmException {
		KeyGenerator generator = KeyGenerator.getInstance("AES");
		SecureRandom rand = new SecureRandom();
		generator.init(rand);
		SecretKey secretKey = generator.generateKey();
		return secretKey;
	}
	private static void cipherFile(SecretKey secretKey,int mode,String inFile,String outFile)throws Exception{
		Cipher cipher = Cipher.getInstance("AES");
		cipher.init(mode, secretKey);
		
		int blockSize = cipher.getBlockSize();
		byte[] inbuff  = new byte[blockSize];
		
		String source = ClassLoader.getSystemResource(inFile).getFile();
		String chiper = ClassLoader.getSystemResource(outFile).getFile();
		FileInputStream in   = new FileInputStream(source);
		FileOutputStream out = new FileOutputStream(chiper);
		
		while(true){
			int inlen = in.read(inbuff);
			System.out.println(inlen);
			if(inlen == blockSize){
				out.write(cipher.update(inbuff));
			}else if(inlen > 0){
				out.write(cipher.doFinal(inbuff,0,inlen));//如果在读取中出现字节数小于bolckSize 这样它会生成如下填充：inlen=1 xx 01;inlen=2 xx 02 02;inlen=3 xx 03 03 03
				break;
			}else{
				out.write(cipher.doFinal());//如果读取的所有字节数刚好被blockSize整除执行cipher.doFinal()产生如下填充：blockSize个[0blocakSize]
				break;
			}
		}
		out.flush();
		out.close();
		in.close();
	}

AES是一种对称密码，所以加密和解密的时候要用要同一个密钥。

		SecretKey secretKey = generatorKey();
//Cipher.ENCRYPT_MODE加密
		cipherFile(secretKey,Cipher.ENCRYPT_MODE,"source.text","cipher.text");
//Cipher.DECRYPT_MODE解密
cipherFile(secretKey,Cipher.DECRYPT_MODE,"cipher.text","sourcecopy.text");

密码流：CipherInputStream和CipherOutputStream他们提供了可以传入Cipher对象的构造函数，可方便的对流中的信息加密解密

		//下面为解决AES密钥的发布 解决方案，AES密钥为对称密钥，每次产生的密钥都需要在双方之间发送这显然是不安全的
		KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
		int keysize = 512;
		SecureRandom rand = new SecureRandom();
		generator.initialize(keysize, rand);
		KeyPair keyPair = generator.generateKeyPair();
		PrivateKey privateKey = keyPair.getPrivate();
		PublicKey  publicKey  = keyPair.getPublic();
		
		Key key = null;//这是一个AES的密钥
		Cipher cipher = Cipher.getInstance("RSA");
		cipher.init(Cipher.WRAP_MODE, publicKey);//用RSA公钥加密AES密钥
		byte[] wrappedKey = cipher.wrap(key);
		
		cipher.init(Cipher.UNWRAP_MODE, privateKey);//用RSA私钥解密AES密钥
		cipher.unwrap(wrappedKey, "AES", Cipher.SECRET_KEY);

一下是对加密解密的简单封装，可以当作工具类使用：

package Crypto;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
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.Key;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.util.Arrays;

import javax.crypto.Cipher;
import javax.crypto.CipherOutputStream;
import javax.crypto.KeyGenerator;

public class Crypto {
	private static final String AES = "AES";
	private static final String RSA = "RSA";
	
	public static Key genAndSaveKey( String filename )throws Exception{
		Key key = Crypto.genKey();
		Crypto.saveKey(filename, key);
		return key;
	}
	
	public static Key genKey() throws NoSuchAlgorithmException{
		KeyGenerator keygen = KeyGenerator.getInstance(AES);
		SecureRandom random = new SecureRandom();
		keygen.init(random);
		return keygen.generateKey();
	}
	
	public static boolean saveKey( String filename , Key key )throws IOException{
		File file = new File(filename);
		if( file.exists() ){
			ObjectOutputStream out = null;
			try{
				out = new ObjectOutputStream(new FileOutputStream(file));
				out.writeObject(key);
				out.flush();
				return true;
			}finally{
				if( out != null ) out.close();
			}
		}
		return false;
	}
	
	public static Key readKey( String filename )throws IOException, ClassNotFoundException{
		File file = new File(filename);
		if( file.exists() ){
			ObjectInputStream out = null;
			try{
				out = new ObjectInputStream(new FileInputStream(file));
				return (Key) out.readObject();
			}finally{
				if( out != null ) out.close();
			}
		}
		return null;
	}
	
	public static byte[] encrypt( byte[] buf , Key key ) throws Exception{
		return crypt(buf, key, Cipher.ENCRYPT_MODE);
	}
	
	public static byte[] decrypt( byte[] buf , Key key ) throws Exception{
		return crypt(buf, key, Cipher.DECRYPT_MODE);
	}
	
	public static byte[] crypt0( byte[] buf , Key key , int mode) throws Exception{
		Cipher cipher = Cipher.getInstance(AES);
		cipher.init(mode, key);
		int blockSize = cipher.getBlockSize();
		int outSize   = cipher.getOutputSize(blockSize);
		
		byte[] inbytes  = new byte[blockSize];
		byte[] outbytes = new byte[outSize];
		
		ByteArrayInputStream  inStream 	= new ByteArrayInputStream(buf);
		ByteArrayOutputStream outStream = new ByteArrayOutputStream();
		
		int inLength = 0;
		while( (inLength = inStream.read(inbytes)) == inbytes.length ){
			int outLength = cipher.update( inbytes , 0 , inbytes.length , outbytes );
			outStream.write( outbytes , 0 , outLength );
		}
		
		if( inLength > 0 ){
			outbytes = cipher.doFinal(inbytes, 0, inLength);
		}else{
			outbytes = cipher.doFinal();
		}
		outStream.write(outbytes);
		
		return outStream.toByteArray();
	}
	
	public static byte[] crypt( byte[] buf , Key key , int mode) throws Exception{
		Cipher cipher = Cipher.getInstance(AES);
		cipher.init(mode, key);
		CipherOutputStream 	  cipoStream = null;
		ByteArrayOutputStream buffStream = new ByteArrayOutputStream();
		try {
			cipoStream = new CipherOutputStream(buffStream, cipher);
			cipoStream.write(buf);
		}finally{
			if( cipoStream != null ) cipoStream.close();
		}
		return buffStream.toByteArray();
	}
	
	public static KeyPair genKeyPair() throws NoSuchAlgorithmException{
		KeyPairGenerator genkey = KeyPairGenerator.getInstance(RSA);
		SecureRandom random = new SecureRandom();
		genkey.initialize(512, random);
		return genkey.generateKeyPair();
	}
	
	public static byte[] encryptKey(Key key , PublicKey publicKey) throws Exception{
		Cipher cipher = Cipher.getInstance(RSA);
		cipher.init(Cipher.WRAP_MODE, publicKey);
		return cipher.wrap(key);
	}
	
	public static Key decryptKey(byte[] wrappedKey, PrivateKey privateKey) throws Exception{
		Cipher cipher = Cipher.getInstance(RSA);
		cipher.init(Cipher.UNWRAP_MODE, privateKey);
		return cipher.unwrap(wrappedKey, AES, Cipher.SECRET_KEY);
	}
	
	public static void main(String[] args) throws Exception {
		String filename = ClassLoader.getSystemClassLoader().getResource("resource/key").getFile();
		Key key = Crypto.readKey(filename);
		
		KeyPair keyPair = genKeyPair();
		PublicKey publicKey = keyPair.getPublic();
		PrivateKey privateKey = keyPair.getPrivate();
		
		byte[] wrappedKey = encryptKey(key, publicKey);
		key = decryptKey(wrappedKey, privateKey);
		
		byte[] bytes = encrypt("luoxun".getBytes(), key);
		System.out.println(Arrays.toString(bytes));
		byte[] decode = decrypt(bytes, key);
		System.out.println(new String(decode));
		
	}
	
}