Easy VAPID generation

A set of VAPID encoding libraries for popular languages.

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VAPID is a draft specification for providing self identification. see https://datatracker.ietf.org/doc/draft-ietf-webpush-vapid/ for the latest specification.

TL;DR:

In short, you create a JSON blob that contains some contact information about your WebPush feed, for instance:

{
    "aud": "https://YourSiteHere.example",
    "sub": "mailto://[email protected]",
    "exp": 1457718878
}

You then convert that to a JWT encoded withalg = "ES256". The resulting token is the Authorization header "Bearer ..." token, the Public Key used to sign the JWT is added to the Crypto-Key set as "p256ecdsa=..."