Thread: Setting up a loop for a SHA-256 hash for multiple outputs

Originally Posted by Norm

methods must all be defined at the class level. The code for a method must be inside a {} pair.
Move the prependZeros() method after the } that ends the method where it was coded in post#16

I'll give it a go. Taking a break for a few hours and will let you know what I get.

Originally Posted by Norm

methods must all be defined at the class level. The code for a method must be inside a {} pair.
Move the prependZeros() method after the } that ends the method where it was coded in post#16

I moved it like you said, but it still must be recognizing it as a method in a method. will use // to describe what I am trying to do.

import java.security.MessageDigest;
 
public class SHAHashingExample  {
    public static void main(String[] args)throws Exception {
    	String a = "0000000000000000"; // defines Original value
 
        for (int b=Integer.parseInt(a);b<=17;b++); { 
		String strHexNumber = Integer.toHexString(b); // loop to change integer to a hex value 
		}
		String prependZeros(int b); { // number >= 0  **Compiling Error at parantheses**
		String s= "000000000000000000"+b; // 16 zeros prepended
		return s.substring(s.length()-16); // keep the rightmost 16 chars  
			System.out.println("Original : " + strHexNumber); // Outputs 17 hex values from 0 to 11
			}	
		MessageDigest md = MessageDigest.getInstance("SHA-256");
        	md.update(a.getBytes());
 
        	byte byteData[] = md.digest();
 
        	//convert the byte to hex format
        	StringBuffer hexString = new StringBuffer();
    		for (int i=0;i<byteData.length;i++) {
    			String hex=Integer.toHexString(0xff & byteData[i]);
   	     		if(hex.length()==1) hexString.append('0');
   	     		hexString.append(hex);
    		        }
        	System.out.println("Hash : " + hexString.toString()); //Output of Hash
 
    }
}

Trying to compile, I still get:

SHAHashingExample.java:11: error: ';' expected
	String prependZeros(int b); { // number >= 0
                           ^
SHAHashingExample.java:11: error: ';' expected
	String prependZeros(int b); { // number >= 0
                                 ^
2 errors

Do I need a different variable besides b now so it will compile? I'm not sure what I am missing since I feel like I have tried everything else. But will keep working.

Originally Posted by Norm

methods must all be defined at the class level. The code for a method must be inside a {} pair.
Move the prependZeros() method after the } that ends the method where it was coded in post#16

import java.security.MessageDigest;
 
public class SHAHashingExample  {
    public static void main(String[] args)throws Exception {
    	String a = "0000000000000000"; // defines Original value
 
        for (int b=Integer.parseInt(a);b<=17;b++); { 
		String strHexNumber = Integer.toHexString(b); // loop to change integer to a hex value 
		}
 		String prependZeros(int b); { // number >= 0  **Compiling Error at parantheses**
		String s= "000000000000000000"+b; // 16 zeros prepended
		return s.substring(s.length()-16); // keep the rightmost 16 chars 
		}
		System.out.println("Original : " + strHexNumber); // Outputs 17 hex values from 0 to 17
 
		MessageDigest md = MessageDigest.getInstance("SHA-256");
        	md.update(a.getBytes());
 
        	byte byteData[] = md.digest();
 
        	//convert the byte to hex format
        	StringBuffer hexString = new StringBuffer();
    		for (int i=0;i<byteData.length;i++) {
    			String hex=Integer.toHexString(0xff & byteData[i]);
   	     		if(hex.length()==1) hexString.append('0');
   	     		hexString.append(hex);
    		        }
        	System.out.println("Hash : " + hexString.toString()); //Output of Hash
 
    }
}

I've moved the code to this now, still get same compiling error. When you say "method", do you mean the for loop statement or do you mean I have to create a whole new section with a new "public static void main(String[] args) {" that begins at every coding... But I don't think that will help. Hahaha I feel like I am so close too!

Finally got it with a little bit of help from other sources.

import java.security.MessageDigest;
public class SHAHashingExample 
{
	public static void main(String[] args)throws Exception
	{
		for(int j=0; j<17; j++) // loop to create consecutive "Original" output
		{
			String a = "0000000000000000"; // Define Starting number
			a=appendHash(j,a); // replaces the last digit(s) of a, with the value in j 
			MessageDigest md = MessageDigest.getInstance("SHA-256");
			md.update(a.getBytes());
 
			byte byteData[] = md.digest();
 
			//convert the byte to hex 
			StringBuffer hexString = new StringBuffer();
			for (int i=0;i<byteData.length;i++) 
			{
				String hex=Integer.toHexString(0xff & byteData[i]);
				if(hex.length()==1) hexString.append('0');
				hexString.append(hex);
			}
			System.out.println("Original : " + a); // outputs original 16 digit hex code         
			System.out.println("Hash : " + hexString.toString()); //outputs Hash of Original
		}
	}
 
 
 
 
	public static String appendHash(int b, String s) // New Method defined to keep 16 digit hex
	{
		s+=Integer.toHexString(b); // convert b to a hex, and only then appends it to s 
 
		return s.substring(s.length()-16); // keep the rightmost 16 chars 
 
	}
}

I wasn't quite sure what you meant by new method until it was explained to me to place it under it's own "public static etc". What you said makes WAY more sense now! Made a few other changes and put // next to them as I understood what line does what. Thanks again!

Originally Posted by Norm

Is it working now?

Yes, but I guess I was curious what changes I could make to reference this as "long" expressions instead of int. Int is only 32 bit and could only do the first 2147483647 (16^8-1) without error. My original intention was to do the entire string of 18 quintillion+ possible hashes from 0000000000000000 to ffffffffffffffff, but forgot it's max limit. My computer is STILL processing the program so I can test the speed and how soon it will actually be done with just 2 billion. Even with long expression, the max I can get is 9223372036854775808 and I'd just run it twice with different limits. That's one big text file... HAHA!

But thanks again guys unless you want to assist with anything of the above I mentioned.