How to loop in the file of array byte

Question

public byte[][] createShares(byte[] secret, int shares, int threshold, Random rnd) 

{
// some code here
}

I have this method and i am going to apply SSS for file of byte array . byte [] secret is method parameter where i am going to pass as argument each byte of the file and then apply for each byte the SSS algorithm. I have also implemented a java code of how to read the file and then convert it to a byte array. I am stuck of how to implement this SSS algorithm for each byte of files. I know i need a for loop for that . The point is i want to call to my main method this byte [] secret and assign to it each byte of the file but i am stuck of how to do it .

My method which will read the file and convert it to the array of bit is as below:

public  byte[] readFile(File fileName) throws IOException {
      InputStream is = new FileInputStream(fileName);

  // Get the size of the file
  long length = fileName.length();


  // to ensure that file is not larger than Integer.MAX_VALUE.
  if (length > Integer.MAX_VALUE) {
    throw new IOException("Could not completely read file " + fileName.getName() + " as it is too long (" + length + " bytes, max supported " + Integer.MAX_VALUE + ")");
  }

  // Create the byte array to hold the data
  byte[] secret = new byte[(int)length];


  int offset = 0;
  int numRead = 0;
  while (offset < secret.length && (numRead=is.read(bytes, offset, bytes.length-offset)) >= 0) {
      offset += numRead;
  }

  // Ensure all the bytes have been read in
  if (offset < secret.length) {
      throw new IOException("Could not completely read file " + fileName.getName());
  }

  // Close the input stream and return bytes
  is.close();
  return secret;


 }

Can anyone help me how to loop for each byte of the file and then pass it as the argument to my createshares method ?

You should use any of this methods to read the file (so you are not reinventing the wheel) http://stackoverflow.com/questions/858980/file-to-byte-in-java Also you should explain better your issue. — Paco Abato, Mar 03 '16 at 15:19
@PacoAbato suppose OP tries to implement kind of this: https://en.wikipedia.org/wiki/Shamir's_Secret_Sharing — Alex Salauyou, Mar 03 '16 at 15:25

score 0 · Accepted Answer · answered Mar 03 '16 at 16:39

I understand you are trying to read bytes from the file and also trying to loop through the byte[].

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Random;
import java.nio.file.Path;


public class SSSAlgorithm {

public static void main(String[] args) {
    System.out.println("Reading file");
    try {
        byte[] secret = readFile();
        createShares(secret, 2, 3, 100);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

public static byte[][] createShares(byte[] secret, int shares, int threshold, int i) 
{
    // some code here
    for (byte coeff : secret){
        System.out.println("Use the byte here " + coeff);
    }

    return null;
}


public static byte[] readFile() throws IOException {
    Path path = Paths.get("/Users/droy/var/crypto.txt");
    try {
        byte[] secret = Files.readAllBytes(path);
        return secret;

    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}
}

**Output:

Stored secret as 1234
byte array representation: [49, 50, 51, 52, 10]

Use the byte here 49
Use the byte here 50
Use the byte here 51
Use the byte here 52
Use the byte here 10

this is working fine but still when i use this i do not have my file shared for each byte . I just got something like your output below. Can you help me how can i get each file of my byte shared — john smith, Mar 03 '16 at 18:52
public byte[][] createShares(byte[] secret, int shares, int threshold, Random rnd) {byte[][] share = new byte[shares][m + 1]; for (int i = 0; i < shares; i++) share[i][0] = (byte) (i + 1); byte[] a = null; try { a = new byte[threshold]; for (int i = 0; i < m; i++) { rnd.nextBytes(a); a[0] = secret[i]; for (int j = 0; j < shares; j++) share[j][i + 1] = (byte) eval(share[j][0], a); } } finally { if (a != null) Arrays.fill(a, (byte) 0); } return share; } — john smith, Mar 03 '16 at 18:57

How to loop in the file of array byte

1 Answers1