Using SHA-256 with NodeJS Crypto

Question

I\'m trying to hash a variable in NodeJS like so:

var crypto = require(\'crypto\');

var hash = crypto.createHash(\'sha256\');

var code = \'bacon\';

code = has         


        

Answer 1

Similar to the answers above, but this shows how to do multiple writes; for example if you read line-by-line from a file and then add each line to the hash computation as a separate operation.

In my example, I also trim newlines / skip empty lines (optional):

const {createHash} = require('crypto');

// lines: array of strings
function computeSHA256(lines) {
  const hash = createHash('sha256');
  for (let i = 0; i < lines.length; i++) {
    const line = lines[i].trim(); // remove leading/trailing whitespace
    if (line === '') continue; // skip empty lines
    hash.write(line); // write a single line to the buffer
  }

  return hash.digest('base64'); // returns hash as string
}

I use this code ensure generated lines of a file aren't edited by someone manually. To do this, I write the lines out, append a line like sha256: with the sha265-sum, and then, upon next run, verify the hash of those lines matches said sha265-sum.