I need to

  • encrypt JSON payload (not just sign)
  • not share private key
  • verify the payload is generated with the shared public key and RSA fitting all of these.

As I’ve only made auth with JWT so far, I’m not sure. If I use RSA, I guess I have to put the encrypted text in the body.

Do you think it can be used? Any other suggestions?

  • alex_02@infosec.pubEnglish
    4·
    1 year ago

    Idk why the other person said to not use RSA because of PKCS#1 padding vulns since 2048 RSA-OAEP should be fine for your use case. Just make sure to rotate keys and encrypt first with AES or some other symmetric encryption than RSA. Also, double check the libraries you’re using and try to implent boring encryption which will reduce the probability of a misconfigured encryption algorithm. Also, make sure to secure the private key which can be done a number of ways.

    I personally wouldn’t use RSA for this, but that’s just me.

    • isoOPAEnglish
      1·
      1 year ago

      I don’t want to use RSA too but nothing better comes to my mind :)

      • alex_02@infosec.pubEnglish
        2·
        1 year ago

        This might help: https://www.scottbrady91.com/jose/json-web-encryption

        Looks like it uses RSA so what I said above I think still applies.

        EDIT: It is called JWE or JSON Web Encryption for help with what keywords you should search. There are also other symmetric algos you can use with RSA like chacha20, but I think it is best to start with AES just because it has been used for years and is very well documented.

        • isoOPAEnglish
          1·
          1 year ago

          TIL that RSA allows maximum 245 character payload. But I guess that doesn’t apply to JWE. Thanks for the suggestion, I’m researching 🙏🫡

  • colossus@infosec.pubEnglish
    2·
    1 year ago

    Sounds like you’re proposing WebAuthn which already exists. Keep in mind that there are attacks against RSA with PKCS1 padding. I’d use a more secure cryptographic primitive than RSA (I.e. elliptic curves) - there’s a reason cryptographic experts don’t look towards RSA these days.

  • mwguy@infosec.pubEnglish
    11·
    1 year ago

    If you’re already using JWTs for the auth it seems like JWE.

    However unless you’re storing your tokens and payloads (like in a job queue) that might be overkill. If your standard REST/Graphql api is backed by SSL/TLS you get encryption in transit for free.