Alternative for digital signing applet under Chrom

At the moment we have developed a system that can digitally sign documents using a java applet. However with the ban of applets under chrome we are looking for an alternative solution for digital signing.

At the moment the signing works the following way:

A HTTP GET is sent to a servlet to get the document that is going to be signed;
The applet gets started, the digital signature driver gets extracted from the file system and the user enters the PIN;
The applet gets the certification chain, checks CRLs/OSCP and signs the document;
The applet sends a multipart post with the already signed file to a servlet in the system.

One alternative solution would be to import the certificate in the browser and use js to do the signing. But that won't be an user friendly solution.

Another solution could be to ask the user to download a run a program using JNLP that downloads and signs the document and automatically uploads it using HTTP multipart POST. The drawback of this approach would be it requires additional user interactions (the download action) and we lose browser http session, so we have to authenticate again.

Which is more viable? Can you think of alternative?

All post below suggests RSA based signing.

You may sign it in pure Javascript+ Web Crypto api.

Key points is extracting key with HTML5 <file> tag, use forge js library to deal with keys and hashes and canonize xml with deoxxa and use web crypto for sign/verify (in addition, forge also may sign/verify but web crypto is faster).

If you are signing xmls with exclusive canonicalization, use deoxxa (you should browserify it before using). If you sign xml and need to do inclusive canonicalization use my fork of deoxxa (hosted on own gitlab server). I was too lazy to rename exclusive to inclusive but my .js file performs inclusive, believe me) Example of usage forge+deoxxa+html5_p12_file_read in signJs, verifyJs files.

Also, forge supports signing binary files (CMS or in older naming style PKCS#7) but my JSP files doesn't have such example. About OCSP and chain test in JS - I opened the issue in forge, but it seems too difficult to handle CRL/OCSP and TSP protocols in JS, that's why you may sign in JS, but verify may be splitted - hash checking doing in JS(forge usage and additional code showed in my JSP) but smart checks like CRL, chain e.t.c do in your web service - you may extract X509Certificate and send it to your web service and use bouncycastle or any other cool library to do smart checks. X509Certificate is anyway public info, no problem in sending it to service, but digest checking requires files and you may not want to send files to service and thus use forge for checking digest which is showed in my verifyJS file.

My JS code is not refactored and even not in OOP and currently I'm not working on that project but on some stage I had fully working xml RSA siging with p12 keys in file system.

Latest JSP in my repo uses forge just for parsing p12 files and providing keys from them to Web Crypto API but my repo history also has pure Javascript sign/verify (if you don't like web crypto api). see history of the project branches.