/**
 * push/encryption.ts
 *
 * Browser-push payload encryption, implemented with Node's built-in crypto
 * (node:crypto), no third-party web-push dependency. This is the daemon-side
 * (Node/Bun) delivery path only; nothing here is imported by the runtime-neutral
 * or browser bundles (see scripts/browser-compat-check.ts).
 *
 * Two standards are combined here, exactly as a browser Push service expects:
 *
 *  - RFC 8291 (Message Encryption for Web Push): derive a shared secret from an
 *    ephemeral P-256 keypair and the subscription's public key + auth secret.
 *  - RFC 8188 (aes128gcm content encoding): expand that secret into a
 *    content-encryption key + nonce and encrypt one record, then frame it with
 *    the salt / record-size / sender-public-key header the receiver reads back.
 *
 * The output Buffer is the raw request body sent to the subscription endpoint
 * with `Content-Encoding: aes128gcm`.
 */
/** The subscription's own key material, base64url-encoded (browser PushSubscription shape). */
export interface SubscriptionKeyMaterial {
    /** The receiver's public key, 65-byte uncompressed P-256 point, base64url. */
    readonly p256dh: string;
    /** The receiver's 16-byte authentication secret, base64url. */
    readonly auth: string;
}
export interface EncryptedPushPayload {
    /** The aes128gcm request body: header || ciphertext || GCM tag. */
    readonly body: Buffer;
    /** Always `aes128gcm`, the value for the Content-Encoding request header. */
    readonly contentEncoding: 'aes128gcm';
}
/**
 * Encrypt `plaintext` for a subscription's key material.
 *
 * A fresh ephemeral sender keypair and salt are generated per call (RFC 8291
 * requires this, the same salt/key pair must never encrypt two messages), so
 * the result is non-deterministic by design.
 */
export declare function encryptPushPayload(keys: SubscriptionKeyMaterial, plaintext: Buffer): EncryptedPushPayload;
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