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Tuesday, July 19, 2016
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Creating digests (e.g. SHA-256)

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Example

// Convert string to ArrayBuffer. This step is only necessary if you wish to hash a string, not if you aready got an ArrayBuffer such as an Uint8Array.
var input = new TextEncoder('utf-8').encode('Hello world!');

// Calculate the SHA-256 digest
crypto.subtle.digest('SHA-256', input)
// Wait for completion
.then(function(digest) {
  // digest is an ArrayBuffer. There are multiple ways to proceed.

  // If you want to display the digest as a hexadecimal string, this will work:
  var view = new DataView(digest);
  var hexstr = '';
  for(var i = 0; i < view.byteLength; i++) {
    var b = view.getUint8(i);
    hexstr += '0123456789abcdef'[(b & 0xf0) >> 4];
    hexstr += '0123456789abcdef'[(b & 0x0f)];
  }
  console.log(hexstr);

  // Otherwise, you can simply create an Uint8Array from the buffer:
  var digestAsArray = new Uint8Array(digest);
  console.log(digestAsArray);
})
// Catch errors
.catch(function(err) {
  console.error(err);
});

The current draft suggests to provide at least SHA-1, SHA-256, SHA-384 and SHA-512, but this is no strict requirement and subject to change. However, the SHA family can still be considered a good choice as it will likely be supported in all major browsers.