Java安全（JCA/JSSE）：非对称加密

读一个流这个buffer到底设置多大？你根本就不会知道

所以用下面的方法

privatestaticvoid copyStream(InputStream is,OutputStream os)
throws Exception{
byte[] buff=newbyte[1024];
int
total=0;
int len=is.read(buff);
while(len!=-1){
os.write(buff, 0, len);
len=is.read(buff);
}



或者



byte[] src=newbyte[fisDat.available()];//对于文件流来说就是其长度，而对于像网络流就不是了
int len=fisDat.read(src);
int total=0;
while(total<src.length){
total+=len;
len=fisDat.read(src, total, src.length-total);
}



公钥加密私钥解密
package com.xiongshiyan.security;

import
java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
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 javax.crypto.Cipher;
import
javax.crypto.CipherInputStream;
import javax.crypto.CipherOutputStream;
import
javax.crypto.NoSuchPaddingException;

publicclass PublicSecretTest {

/**
* @param args
* @throws Exception

*/
publicstaticvoid main(String[] args)
throws Exception {
//
TODO Auto-generatedmethod stub

PublicSecretTest.publicEnrypt();
PublicSecretTest.privateDerypt2();
}
privatestaticvoid publicEnrypt()
throws Exception{
Cipher cipher = Cipher.getInstance("RSA");
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
KeyPair keyPair = keyPairGenerator.generateKeyPair();
PublicKey publicKey=keyPair.getPublic();
PrivateKey privateKey=keyPair.getPrivate();
cipher.init(Cipher.ENCRYPT_MODE, publicKey);//使用公钥加密
byte[] secResult = cipher.doFinal("熊诗言".getBytes());
System.out.println(new String(secResult));
//把加密后的数据和key一起给别人
别人拿到了之后进行恢复
ObjectOutputStream oosKey=new ObjectOutputStream(new
FileOutputStream("key2.key"));
oosKey.writeObject(privateKey);//写入加密key
oosKey.close();

FileOutputStream oosDat=new FileOutputStream("dat2.dat");
oosDat.write(secResult);//写入加密dat
oosDat.close();

}
privatestaticvoid
privateDerypt() throws Exception{
ObjectInputStream oisKey=new ObjectInputStream(new
FileInputStream("key2.key"));
Key key=(Key)oisKey.readObject();
oisKey.close();

Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, key);

FileInputStream fisDat=new FileInputStream("dat2.dat");
/*
ByteArrayOutputStream baos=new ByteArrayOutputStream();
SecretKeyTest.copyStream(fisDat,
baos);
byte[] deSecResult=cipher.doFinal(baos.toByteArray());*/

byte[] src=newbyte[fisDat.available()];//对于文件流来说就是其长度，而对于像网络流就不是了
int len=fisDat.read(src);
int total=0;
while(total<src.length){
total+=len;
len=fisDat.read(src, total, src.length-total);
}

byte[] deSecResult=cipher.doFinal(src);
System.out.println(new String(deSecResult));

}



privatestaticvoid privateDerypt2()
throws Exception{
ObjectInputStream oisKey=new ObjectInputStream(new
FileInputStream("key2.key"));
Key key=(Key)oisKey.readObject();
oisKey.close();

Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, key);

FileInputStream fisDat=new FileInputStream("dat2.dat");
/*
ByteArrayOutputStream baos=new ByteArrayOutputStream();
SecretKeyTest.copyStream(fisDat,
baos);
byte[] deSecResult=cipher.doFinal(baos.toByteArray());*/

/*byte[]
src=newbyte[fisDat.available()];//对于文件流来说就是其长度，而对于像网络流就不是了
int len=fisDat.read(src);
int total=0;
while(total<src.length){
total+=len;
len=fisDat.read(src, total,src.length-total);
}

byte[] deSecResult=cipher.doFinal(src);
System.out.println(new String(deSecResult,"utf-8"));*/



//使用CipherInputStream,在读的过程中解密
/*CipherInputStreamcipherInputStream=new CipherInputStream(fisDat,cipher);
ByteArrayOutputStream
baos=new ByteArrayOutputStream();
PublicSecretTest.copyStream(cipherInputStream,
baos);
baos.close();
cipherInputStream.close();
System.out.println(new String(baos.toByteArray(),"utf-8"));*/

//使用CipherOutputStream//在写的时候解密
CipherOutputStream
cipherOutputStream=new CipherOutputStream(System.out,cipher);
PublicSecretTest.copyStream(fisDat,cipherOutputStream);
cipherOutputStream.close();
fisDat.close();


}
privatestaticvoid copyStream(InputStream is,OutputStream
os) throws Exception{
byte[] buff=newbyte[1024];
int
total=0;
int len=is.read(buff);
while(len!=-1){
os.write(buff, 0, len);
len=is.read(buff);
}
}
}



数字摘要：就是数据的指纹，任何两个数据的指纹都不一样，并且都是128位的
一般下载的文件使用一个工具算出它的md5码与给你的比较，如果一样表示没有被破坏



数据校验
数据库密码