Model Crypto (Go WASM)

Browser-side decryption package for encrypted SOG Gaussian model files stored in R2.

Build

cd wasm/model-crypto
./scripts/build.sh "your-arbitrary-key-string" "citizenshub.app,localhost"

• 1st arg: key material (arbitrary string / hex: / base64:)
• 2nd arg (optional): allowed hostnames for origin check, comma-separated (default: citizenshub.app)
• Env key fallback: MODEL_CRYPTO_BUILD_KEY, CCU_HISTORY_BUILD_KEY, CCU_HISTORY_ENCRYPTION_KEY
• Env host fallback: MODEL_CRYPTO_ALLOWED_HOSTS, CCU_HISTORY_ALLOWED_HOSTS, CCU_HISTORY_ALLOWED_HOST

The build script will:

• derive a 16-byte key with SHA-256 using the same rule as the Worker backend and ccu-history-crypto
• compile src/main.go to pkg/cmc.wasm
• copy Go runtime loader to pkg/wasm_exec.js

Usage

import { fetchModelBytes } from '@eduarte/cmc';
import wasmUrl from '@eduarte/cmc/cmc.wasm?url';
import wasmExecUrl from '@eduarte/cmc/wasm_exec.js?url';

const fileBytes = await fetchModelBytes(modelUrl, {
  encrypted: true,
  algorithm: 'xtea-ctr-v1',
  nonce: model.encryptionNonce,
  wasmUrl,
  wasmExecUrl
});

Pass fileBytes into Spark's SplatMesh({ fileBytes, fileName }).

Behavior

• Uses the same XTEA-CTR implementation, static nonce convention, key derivation, and Go WASM hostname check as ccu-history-crypto.
• Intended for binary payloads, not JSON envelopes.
• SOG uploads are encrypted on the Worker before being stored in R2. R2 custom metadata carries encrypted, algorithm, nonce, and original content details.