# Covid Certificate Checker Library
This Javascript-Library is for parsing and verifying EU Electronic Health Certificates (like the digital EU Covid Certificate) in Web-Applications.
## Why another Library
There are already some great Javascript-Libraries, who are helping to decode and verify a digital Covid-Certificate. 
But most of them targets a NodeJS Environment or make it necessary to use polyfills for NodeJS-Functions. 
Like the Buffer-Api or the NodeJS-Crypto-Module. The library is intended for web browsers and mobile first.
## How does it work?
Have a look at the official repository of the European eHealth network. 
There is a [overview](https://github.com/ehn-dcc-development/hcert-spec/blob/main/README.md) about the Design Principals. And also a [rudimentary Implementation-Example](https://github.com/ehn-dcc-development/ehn-sign-verify-javascript-trivial).
## Usage
You can easily use the Library as ES6 Module.

### Install
``npm i covid-certificate-checker``
### Read Certificate
```
import ElectronicHealthCertificateChecker from "covid-certificate-checker";

//Readout String form QR-Code
const testCertificate = "HC1:....";
const healthCertificateClaim = ElectronicHealthCertificateChecker.decode(testCertificate);
console.log(healthCertificateClaim);
```
Example:
```
{
  "iss": "DE",
  "iat": 1643356073,
  "exp": 1622316073,
  "hcert": {
    "v": [
      {
        "ci": "URN:UVCI:01DE/IZ12345A/5CWLU12RNOB9RXSEOP6FG8#W",
        "co": "DE",
        "dn": 1,
        "dt": "2021-05-29",
        "is": "Robert Koch-Institut",
        "ma": "ORG-100031184",
        "mp": "EU/1/20/1507",
        "sd": 2,
        "tg": "840539006",
        "vp": "1119349007"
      }
    ],
    "dob": "1964-08-12",
    "nam": {
      "fn": "Mustermann",
      "gn": "Erika",
      "fnt": "MUSTERMANN",
      "gnt": "ERIKA"
    },
    "ver": "1.0.0"
  }
}
```

### Verify Signature
There are two ways to verify the signature. You can use a Document Signing Certificate like published in the German DSCList (field rawData):
* [Test Document Signing Certificate List](https://de.test.dscg.ubirch.com/trustList/DSC/)
* [Production Document Signing Certificate List](https://de.dscg.ubirch.com/trustList/DSC/)
* [Schema Definition](https://github.com/Digitaler-Impfnachweis/certification-apis/tree/master/dsc-update)

For Verifying it's required that the Browser supports the Web Crypto Api
```
const {
  healthCertificateClaim,
  isVerified
} = await ElectronicHealthCertificateChecker.verify(testCertificate, rawKey);
```
Or you can verify the Signature by submitting a TrustList-Object in the format of the German DSCList. The matching is done over the Key Identifier (kid).
```
const {
  healthCertificateClaim,
  isVerified
} = await ElectronicHealthCertificateChecker.verifyWithTrustList(testCertificate, trustList);
```

## Inspiration
Other projects and libraries I used as inspiration:
* [Simple Javascript Implementation of Sign and Verify](https://github.com/ehn-dcc-development/ehn-sign-verify-javascript-trivial)
* [Digital Covid Certificate Library](https://github.com/btielen/covid-certificate)
* [DCC-Utils Implementation of the Italien Health Ministry](https://github.com/ministero-salute/dcc-utils)
* [COVID Tracker App of Ireland](https://github.com/HSEIreland/covid-tracker-app)

## Build
The build is done with the Typescript-Compiler. Run ``npm run build``.
## Testing
You can run the [Jasmine-Tests](https://jasmine.github.io/setup/browser.html) with ``npm run test:serve`` or ``npm run test``.
## Further Readings
* [Hert Spec](https://github.com/ehn-dcc-development/hcert-spec/blob/main/hcert_spec.md)
* [Technical Specifications](https://ec.europa.eu/health/system/files/2021-04/digital-green-certificates_v3_en_0.pdf)
## Contribute
You can find Testdata under: [DGC Testdata](https://github.com/eu-digital-green-certificates/dgc-testdata)
## Contribute
The classes I wrote in the src folder are under the MIT license. Not affected by this are for example used schemas, Qr-Codes, files, Documentation or test data that come from other authors.
Please feel free to contribute or contact me if you have some Questions.