Sign data using private key on client-side (javascript)

Question

I know, it looks strange, but I need to sign some data on client-side using javascript only, no ajax backdoor to server-side openssl available. Could someone suggest some client-side solution to sign data using private key? Is it possible?

Thanks.

Madrigal

Answer 1

Found great signing tool. It implements RSA-SHA1 (works perfectly) and RSA-SHA256 (works strange), and allow both to generate signature using private key and to verify signature using certificate.

Madrigal

How can we use it? Is there any simple sample for signing? – Cabalist

Answer 2

The W3C Web Cryptography API may be able to help. Can I use indicates modern browsers now support it.

For additional digital signature support, look at GlobalSign/PKI.js

PKIjs is a pure JavaScript library implementing the formats that are used in PKI applications (signing, encryption, certificate requests, OCSP and TSP requests/responses). It is built on WebCrypto (Web Cryptography API) and requires no plug-ins. http://pkijs.org

Trolly

For API docs I found mozilla's, especially SubtleCrypto -> sign() – Porett

Answer 3

I've gone down the same road as you, you're probably better off implementing something like oAuth.

The problem with what you're proposing is that there's absolutely no reliable way of storing the private key on the client machine, nor of now securely getting the public key back to the server other than HTTPS (and if you're using HTTPS, what's the point of this?)

If you really want to continue, there are some implementations out there: http://shop-js.sourceforge.net/crypto2.htm

And you probably want something horribly annoying like PersistJS (http://pablotron.org/?cid=1557) to try and save the private key as long as possible.

Frisian

Thank you for suggestion. I have already played with this tool, this is for symmetric encryption/decryption, but I need asymmetric signing/verifying, like in nodejs crypto module: sign some data (not encode) using private key, and verify in another script (using native openssl verifier by certificate) – Madrigal

Ahh, sorry, I mis-interpreted your question. Mind if I ask what the point is? Unless you have access to a key on the user's disk, all you're doing is validating that you're speaking with the same user that you previously did, and since the traffic is from client-server encryption performs the same task, doesn't it? Mozilla has a built-in crypto object if you have the luxury of telling people to use Firefox. – Frisian

My goal is demonstrate standalone client which can digitally sign some data. I dont care about security, safe storing private key. This is prototype for demonstrating purposes only. – Madrigal

@Mark Kahn given the choice of signing and keeping my private key in my machine or uploading the (decrypted) private key to a server to sign a document I'd choose the former. – Veolaver

Answer 4

Web Crypto appears to be the answer. Here is a tutorial (not mine). As for the comment, if you are using https, why do you need signing - these are needed for two different purposes. In infosec lingo, the former gives confidentiality and the latter non-repudiation.

Aftergrowth

Answer 5

You can use jose

    import * as jose from 'jose'
    const privateKey= '449f9c8d5a4b71c829f2f670965bd67fd5332a146019r0870a2a659e114c185d'
    const SECRET_KEY = new TextEncoder().encode(privateKey)
    const payload = {
      params: {
        example: 'Hi'
      }
    }
    const alg = 'HS256'
    const token = await new jose.SignJWT(payload)
      .setProtectedHeader({ alg })
      .setIssuedAt()
      .setIssuer('urn:example:issuer')
      .setAudience('urn:example:audience')
      .setExpirationTime('2h')
      .sign(SECRET_KEY)

Note: If you put the privateKey in js client, it is indeed insecure.

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