Require information on decoding/decompressing the QR certificate information

[venkyms]

Hi All
I am working on a java solution to read the Vaccination QR certificate. I am able to read the QR code but need some reference on how to decode the data in the certificate. I saw the JS implementation uses JSZIP to decode the document but while I try similar unzip using gzip, I am unable to do so.

Is there any reference guide to decode the certificate data read from the QR code?

Thanks!

[dileepbapat]

standard zip format will work for deflate, please note gzip will not work.

[shahns]

@venkyms have you figured out which apis for qr code are working correctly? I think most of the readers out there do not support the encoding or partially output the string with some bytes missing (such as zxing based java and react libraries). Which library are you using and what alternative are you using for JSZip?

[di1]

zxing works, I will try to share the sample shortly (binary mode, raw bytes)

[shahns]

@di1 Thanks! That would be really great!

I tried zxing java library--I could get raw bytes and write them to a file.

Upon trying file --mime <filename> I get mime-type as octate-sream (which should be zip) with binary charset (QR code string conforms to zip header in little endianess 0x04034b50). Extraction using unzip locally was not successful and gives following error.

Archive: certificate.json warning [certificate.json]: 818 extra bytes at beginning or within zipfile (attempting to process anyway) error [certificate.json]: start of central directory not found; zipfile corrupt. (please check that you have transferred or created the zipfile in the appropriate BINARY mode and that you have compiled UnZip properly)

In my application I am using zip4j in place of JSZip.

[shahns]

@di1 have you posted the code snippet or gist somewhere?

Thanks!

[di1]

https://gist.github.com/di1/b187c778b255f2f639ba4bb49d160eeb