几种加密算法的java实现包括MD5、RSA、SHA256

SHA加密：

package com;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* 对外提供getSHA(String str)方法
* @author randyjia
*
*/
public class SHA {
public static String Encrypt(String strSrc, String encName) {
MessageDigest md = null;
StringBuilder sb = new StringBuilder();

byte[] bt = strSrc.getBytes();
try {
md = MessageDigest.getInstance(encName);
byte[] result = md.digest(bt);
for (byte b : result) {
sb.append(String.format("%02x", b));
}
} catch (NoSuchAlgorithmException e) {
return null;
}
return sb.toString();
}


public static void main(String args[]){
String s = SHA.Encrypt("12345", "SHA-256");
System.out.println(s);

}
}

RSA加密：

package com;

import java.io.*;
import java.security.*;

import javax.crypto.*;
import java.security.spec.X509EncodedKeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import sun.misc.*;

public class Rsa_test {
private KeyPairGenerator kpg = null;
private KeyPair kp = null;
private PublicKey public_key = null;
private PrivateKey private_key = null;

public Rsa_test(int in, String address) throws NoSuchAlgorithmException,
FileNotFoundException, IOException
{
kpg = KeyPairGenerator.getInstance("RSA");
kpg.initialize(in);
kp = kpg.genKeyPair();
public_key = kp.getPublic();
private_key = kp.getPrivate();

sun.misc.BASE64Encoder b64 = new sun.misc.BASE64Encoder();
String pkStr = b64.encode(public_key.getEncoded());
String prStr = b64.encode(private_key.getEncoded());
System.out.print("pkStr length:" +pkStr.length()+" "+pkStr);

FileWriter fw=new FileWriter(address + "/private_key.dat");
fw.write(prStr);
fw.close();

FileWriter fw2 = new FileWriter(address + "/public_key.dat");
fw2.write(pkStr);
fw2.close();
}

private static String encrypt(String source) throws Exception{

FileReader fr = new FileReader("E://public_key.dat");
BufferedReader br=new BufferedReader(fr);
String getPbKey = "";
while(true){
String aLine = br.readLine();
if(aLine==null)break;
getPbKey += aLine;
}
System.out.println( "myBuilderStr : length: " + getPbKey.length() +" "+getPbKey );
BASE64Decoder b64d = new BASE64Decoder();
byte [] keyByte = b64d.decodeBuffer(getPbKey);
X509EncodedKeySpec x509ek = new X509EncodedKeySpec(keyByte);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PublicKey publicKey = keyFactory.generatePublic(x509ek);

Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.ENCRYPT_MODE,publicKey);
byte[] sbt = source.getBytes();
byte [] epByte = cipher.doFinal(sbt);
BASE64Encoder encoder = new BASE64Encoder();
String epStr = encoder.encode(epByte);
return epStr;

}


public static String decrypt(String cryptograph) throws Exception{

FileReader fr = new FileReader("E://private_key.dat");
BufferedReader br=new BufferedReader(fr);
String getPvKey = "";
while(true){
String aLine = br.readLine();
if(aLine==null)break;
getPvKey += aLine;
}
BASE64Decoder b64d = new BASE64Decoder();
byte [] keyByte = b64d.decodeBuffer(getPvKey);
PKCS8EncodedKeySpec s8ek = new PKCS8EncodedKeySpec(keyByte);
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
PrivateKey privateKey = keyFactory.generatePrivate(s8ek);



Cipher cipher = Cipher.getInstance("RSA");
cipher.init(Cipher.DECRYPT_MODE, privateKey);
BASE64Decoder decoder = new BASE64Decoder();
byte[] b1 = decoder.decodeBuffer(cryptograph);
byte[] b = cipher.doFinal(b1);
return new String(b);
}

/*
public static void main(String[] args) {
try {
new Rsa_test(1024, "E:/"); 
System.out.println("");
String getEptStr = encrypt("wuchao");
System.out.println("getEptStr:"+getEptStr);
String drpStr = decrypt(getEptStr);
System.out.println("drpStr:"+drpStr);
}
catch (IOException ex) {
ex.printStackTrace();
}
catch (NoSuchAlgorithmException ex) {
ex.printStackTrace();
}catch(Exception ex){
ex.printStackTrace();
}

}
*/

}

MD5加密：

package com;

import java.security.MessageDigest;

public class Md5 {

public final static String MD5(String s) {
char hexDigits[]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
try {
byte[] btInput = s.getBytes();
MessageDigest mdInst = MessageDigest.getInstance("MD5");
mdInst.update(btInput);
byte[] md = mdInst.digest();
int j = md.length;
char str[] = new char[j * 2];
int k = 0;
for (int i = 0; i < j; i++) {
byte byte0 = md[i];
str[k++] = hexDigits[byte0 >>> 4 & 0xf];
str[k++] = hexDigits[byte0 & 0xf];
}
return new String(str);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.println(Md5.MD5("20121221asfasfasfa"));
System.out.println(Md5.MD5("����"));
}

}