I'm working on a solution where JWE is needed between an Android app and a backend written in Node.JS, using
node-jose. I've been struggling a lot since it seems there is no out of the box compatibility between Android - if you want to use the HW backed keystore - and any node JWE library when it comes to the RSA key, because:
- Android supports these ciphers for the HW backed
AndroidKeyStoreprovider. Note, RSA-OAEP-256 (MGF1 SHA-256) is NOT supported; for some reason Android only supports MGF with SHA-1 even for OAEP-256.
node-joseonly seems to support OAEP schemes with the same MD for OAEP and the MGF:
- RSA OAEP with SHA-1 and no explicit MGF1 (meaning MGF1 SHA-1)
- RSA OAEP with SHA-256 and no explicit MGF1 (meaning MGF1 SHA-256)
- Nimbus JOSE Java library doesn't support the Android KeyStore out of the box, but I've patched it to use
- Nimbus JOSE has deprecated RSA-OAEP (SHA-1) in favor of RSA-OAEP (SHA-256)
The incompatibility is surprising to me, you'd think there would be an off-the-shelf solution for implementing JWE between Node.JS and Android. But I'm wondering about RSA OAEP SHA-1. Nimbus JOSE deprecated it, is it discouraged to use it? Has it been proven vulnerable?
Also, in the future, I want to support the iPhone. I don't know much about iOS, but it seems Apple also has an HW protected key store ("Secure Enclave"). However, it only supports EC!
So if one wanted to build a solution where a mobile phone and a backend server uses JWE for encrypted communication, what's my best bet? My idea is that the mobile app creates a key pair in its hardware-backed Keystore, gives the public key to the backend, and the backend can then create JWEs where the public key is used to encrypt the CEK. But considering Android only supports RSA with some flavors such as RSA OAEP with SHA-256 andMGF1+SHA1, and Apple only supports EC, I guess I'd have to support both RSA and EC on the backend, and if needed patch libraries such as node-jose and node-forge to fit my needs. But perhaps I'm going around this all wrong?
Ref: node-jose issue