verify-chunk

Purpose

Verifies a chunk's Ed25519 signature against the server's public key as the gate that runs on receipt of every chunk — before persistence, before decryption, before reassembly. A mismatched or corrupted signature surfaces as ChunksError(CHUNKS.SIG_INVALID) so callers can drop bad chunks without ever exposing them to the rest of the pipeline.

Features

verifyChunkSig(raw, pubKey): void — reads the embedded signature out of the raw bytes, recomputes the signed payload, and verifies in constant-time via @noble/curves/ed25519.
Single-pass — runs over the original raw buffer without re-encoding.
Throws on failure rather than returning false, matching the rest of the pipeline's error contract.

Usage: Basic Example

import { verifyChunkSig } from "@suaveplan/drive-plugin-chunks";

verifyChunkSig(rawChunk, serverPubKey);
// throws ChunksError(CHUNKS.SIG_INVALID) on mismatch

Usage: Advanced Example

import {
    CHUNKS_CODES,
    ChunksError,
    parseChunk,
    verifyChunkSig,
} from "@suaveplan/drive-plugin-chunks";

async function ingestPeerChunk(raw: Uint8Array) {
    try {
        verifyChunkSig(raw, expectedServerPub);
    } catch (err) {
        if (err instanceof ChunksError && err.code === CHUNKS_CODES.SIG_INVALID) {
            return reportPeerCorruption(raw);
        }
        throw err;
    }
    const parsed = parseChunk(raw);
    return persist(parsed);
}

API Reference

verifyChunkSig(raw: Uint8Array, pubKey: Uint8Array): void — validates that raw carries a correct signature for its embedded metadata + ciphertext under pubKey. Throws ChunksError(CHUNKS.SIG_INVALID) on any failure (including under-length buffers, since parseHeader runs first).

Implementation Notes

The function rebuilds the signed payload as metadata || ciphertext rather than treating the raw bytes as already-signed because the signature occupies a fixed offset between metadata and ciphertext — re-encoding metadata after parsing keeps verification independent of any future header padding changes. suaveplan pins to @noble/curves for both signing and verification, which is constant-time and audited.

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