WebPush.Encryption (web_push v0.1.0)

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aes128gcm content encoding (RFC 8188) layered over the Web Push message encryption (RFC 8291).

Encrypts a plaintext payload into the binary body POSTed to the push service endpoint. The receiving user agent decrypts it with the subscription's private key + auth secret and hands the plaintext to the service worker's push event.

Single-record only: payloads must fit in record_size - 17 bytes (4079 for the default 4096). Notifications are usually well under 250 bytes, so records are never split.

Summary

Functions

encrypt(plaintext, p256dh, auth)

Returns the binary body to POST. p256dh and auth come from the subscription (URL-safe base64, no padding).

encrypt_with(plaintext, p256dh, auth, arg, salt)

Same as encrypt/3 but takes the application-server keypair and salt explicitly, making the output deterministic. Exposed for testing against RFC 8291 §5 vectors; production callers should use encrypt/3.

Functions

encrypt(plaintext, p256dh, auth)

@spec encrypt(plaintext :: binary(), p256dh :: String.t(), auth :: String.t()) ::
  binary()

Returns the binary body to POST. p256dh and auth come from the subscription (URL-safe base64, no padding).

Generates a fresh application-server ECDH keypair and salt for each call.

encrypt_with(plaintext, p256dh, auth, arg, salt)

@spec encrypt_with(
  plaintext :: binary(),
  p256dh :: String.t(),
  auth :: String.t(),
  keypair :: {binary(), binary()},
  salt :: binary()
) :: binary()

Same as encrypt/3 but takes the application-server keypair and salt explicitly, making the output deterministic. Exposed for testing against RFC 8291 §5 vectors; production callers should use encrypt/3.