#Runtime compatibility

#Why this matters

Nagad's protocol uses RSA encryption with PKCS#1 v1.5 padding. Since the fix for CVE-2023-46809 (the Marvin attack), OpenSSL 3.0 builds used by some Node.js versions refuse PKCS#1 v1.5 private-key decryption.

#What we observed

nagad-server declares engines.node >= 18. On Node 22 and 24 it uses node:crypto. On Node 18 and 20 it switches automatically to a BigInt implementation of the decryption step (see below). CI runs the full suite on Node 20, 22 and 24; Node 18 is covered by a full create-and-verify smoke run.

#The capability check

await nagad.init(); // runs checkCapability() on first use

With the default provider on an unsupported runtime, the client switches to the pure-JS decryption. If you passed your own cryptoProvider and it fails the check, NagadCryptoCapabilityError is thrown with the Node and OpenSSL versions instead of failing in the middle of a payment.

#Options on older Node.js

1. Upgrade to Node.js 22 or 24 (recommended; uses the native provider).

2. Do nothing. When you do not set cryptoProvider, nagad.init() (called automatically before the first request) detects the restriction, logs a warning and switches to the pure-JavaScript decryption. You can also choose it explicitly:

   import { createNagad, PureJsCryptoProvider } from 'nagad-server';
   createNagad({ /* … */, cryptoProvider: new PureJsCryptoProvider() });

3. The pure-JS decryption is not constant-time. It decrypts responses that come from Nagad over TLS; it is not meant for an endpoint that accepts attacker-chosen ciphertexts. Only the decryption is pure JavaScript; signing, verifying and encryption still use node:crypto.

4. Running Node with --security-revert=CVE-2023-46809 re-enables the old behaviour. It reintroduces the timing weakness the fix addressed; we do not recommend it.

#Edge runtimes

Cloudflare Workers and Vercel Edge use WebCrypto, which has no RSAES-PKCS1-v1_5. They are not supported. Call a Node.js backend, or use a forward proxy for the egress IP only while keeping signing on Node.