Discussion on: JavaScript: How to decode the GreenPass QR code

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Hi Lorenzo,

Thanks for your post.
I was trying your code using the string contained in my UE QR CODE but when I used decodeAllSync I got the following error :
[ERR_ENCODING_INVALID_ENCODED_DATA]: The encoded data was not valid for encoding utf-8

Any idea of what could have went wrong ?

Lorenzo Millucci • Jul 16 '21

Have you decoded data from Base45 format and have you decompressed it using zlib before using cbor?

Comment deleted

Lorenzo Millucci • Jul 16 '21

I've decoded your QR

{
  "v": [
    {
      "ci": "urn:uvci:....",
      "co": "FR",
      "dn": 2,
      "dt": "2021-07-01",
      "is": "CNAM",
      "ma": "...",
      "mp": "...",
      "sd": 2,
      "tg": "840539006",
      "vp": "...."
    }
  ],
  "dob": "1980-...",
  "nam": {
    "fn": "GR....",
    "gn": "LUD...",
    "fnt": "GR...",
    "gnt": "LUD..."
  },
  "ver": "1.3.0"
}

PS: I suggest you to remove your data from the post above as anyone can decode it

lgrauser • Jul 16 '21

Oh yes thank you. (gonna remove the QR data)

Here's my code

const greenpassJpeg = fs.readFileSync('qrcodelgr.jpg');
const greenpassImageData = jpeg.decode(greenpassJpeg, {useTArray: true});
const decodedGreenpass = jsQR (greenpassImageData.data, greenpassImageData.width, greenpassImageData.height);
console.log('pass decode');
console.log(decodedGreenpass.data);
const greenpassBody = decodedGreenpass.data.substr(4);

const decodedData = base45.decode(greenpassBody);

console.log('Post B45 decode');
console.log(decodedData);

const output = pako.deflate(decodedData);
console.log('apres zlib');
console.log(output);
const results = cbor.decodeAllSync(output);
consol.log('apres decodeallsync');
[headers1, headers2, cbor_data, signature] = results [0] .value;

const greenpassData = cbor.decodeAllSync(cbor_data);

console.log (JSON.stringify(greenpassData[0].get(-260).get (1), null, 2));