SecureRandom 사용하기

package jce;

import java.security.NoSuchAlgorithmException;
import java.util.FormattableFlags;
import java.util.Formatter;


public class SecureRandom {
	public static void main(String[] args) throws NoSuchAlgorithmException {
		java.security.SecureRandom random = java.security.SecureRandom.getInstance("SHA1PRNG");
		byte bytes [] = new byte[16];
		random.nextBytes(bytes);
		
		
		System.out.println(bytesToHexString(bytes));
		
		
	}
	
	public static String bytesToHexString(byte[] bytes){
		/*	StringBuilder sb = new StringBuilder(bytes.length*2);
			Formatter formatter = new Formatter(sb);
			for(byte  b : bytes){
				formatter.format("%02x", b);
			}
			return sb.toString();
			*/
		  final char[] hexArray = {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
	        char[] hexChars = new char[bytes.length * 2];
	        int v;
	        for ( int j = 0; j < bytes.length; j++ ) {
	            v = bytes[j] & 0xFF;
	            hexChars[j * 2] = hexArray[v >>> 4];
	            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
	        }
	        return new String(hexChars);

	}
}

 

 

덤 2. HexTobytes

  public byte[] hexToByteArray(String hex) { 
     if (hex == null || hex.length() == 0) { 
         return null; 
     } 
    
     byte[] ba = new byte[hex.length() / 2]; 
     for (int i = 0; i < ba.length; i++) { 
         ba[i] = (byte) Integer.parseInt(hex.substring(2 * i, 2 * i + 2), 16); 
     } 
     return ba; 
 }