Signing messages with a PCKS12 certificate on the client side (browser)?

Question

Digital certificates

Good afternoon. I wasn’t particularly familiar with cryptography until the last moment, so don’t kick too hard if the question is noob (I’ve been googling this topic for two days, and still nothing).
Disposition: the user accesses the site using his favorite browser via https. Specifies the certificate to be used to establish a connection with the server. The certificate is valid, it is allowed, and it needs to send a text message signed by its certificate to the server.
The server has only the public part of the key, that is, the signature on the server side disappears (this was done to protect against falsification of messages by the server owners).
Actually the question is: is there a way to sign a message with a client certificate on the browser side? I found a solution in JS, but it is based on ActiveX, i.e. exclusively for IE. Signing by hand through the shell is also not suitable.
Thanks in advance for your replies.

Answer 1

The only thing I can advise is to look at the javascript registration code on startssl.com (it's free) - at least a key is generated there by javascript. Perhaps you will find something ... In any case, you will achieve support for this only in ie and ff, nothing works in chrome for the same startssl.
In general, the standard for signing something on the client side is java applets.