AES秘钥生成

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
public class Test{
public static void main(String[] args) {
	getKey();
	getKeyByPass();
}

/**
 * 随机生成秘钥
 */
public static void getKey(){  
    try {  
        KeyGenerator kg = KeyGenerator.getInstance("AES");  
        kg.init(128);//要生成多少位，只需要修改这里即可128, 192或256  
        SecretKey sk = kg.generateKey();  
        byte[] b = sk.getEncoded();  
        String s = byteToHexString(b);  
        System.out.println(s);  
        System.out.println("十六进制密钥长度为"+s.length());  
        System.out.println("二进制密钥的长度为"+s.length()*4);  
    } catch (NoSuchAlgorithmException e) {  
        e.printStackTrace();  
        System.out.println("没有此算法。");  
    }  
}  

/**
 * 使用指定的字符串生成秘钥
 */
public static void getKeyByPass(){
	//生成秘钥
	String password="testkey";
    try {  
        KeyGenerator kg = KeyGenerator.getInstance("AES");  
       // kg.init(128);//要生成多少位，只需要修改这里即可128, 192或256  
        //SecureRandom是生成安全随机数序列，password.getBytes()是种子，只要种子相同，序列就一样，所以生成的秘钥就一样。
        kg.init(128, new SecureRandom(password.getBytes()));
        SecretKey sk = kg.generateKey();  
        byte[] b = sk.getEncoded();  
        String s = byteToHexString(b);  
        System.out.println(s);  
        System.out.println("十六进制密钥长度为"+s.length());  
        System.out.println("二进制密钥的长度为"+s.length()*4);  
    } catch (NoSuchAlgorithmException e) {  
        e.printStackTrace();  
        System.out.println("没有此算法。");  
    }  
} 
/**
 * byte数组转化为16进制字符串
 * @param bytes
 * @return
 */
public static String byteToHexString(byte[] bytes){     
    StringBuffer sb = new StringBuffer();     
    for (int i = 0; i < bytes.length; i++) {     
         String strHex=Integer.toHexString(bytes[i]); 
         if(strHex.length() > 3){     
                sb.append(strHex.substring(6));     
         } else {  
              if(strHex.length() < 2){  
                 sb.append("0" + strHex);  
              } else {  
                 sb.append(strHex);     
              }     
         }  
    }  
   return  sb.toString();     
}  
}