electronic signature development

Hello. This is our project: We want to develop an Advanced e-Signature app to integrate with our software. It must be in accordance with the European Union law, which defines 3 types of e-signatures: Simple, Advanced and Qualified. We want the Advanced version. Basically, 2 things are needed for this: (1) certify with as much data as possible that it was that specific person who signed the document and not somebody else in his/her name; (2) ensure that the document has not been altered after it was signed. The process could be something like this: 1. The salesman sends a URL to the client. The ideal case would be to send it through WhatsApp. But, if not enough information could be collected this way, the link should be sent through email. The client must open the link his/her own cell phone (not the salesman tablet or cell phone). This ensures that the person did it from his/her trusted device. If made through email it also ensures that the person must have accessed his/her personal email to sign the document. The following data should be collected from both the sender and the receiver of the URL: time stamps, geolocation, IP, internet provider, phone model. If possible, it would also be nice to collect the phone number and MAC. All this information is to prove, in the case of a lawsuit, who sent and who signed the document, with as much data as possible. It should prove, for example that they were together in the same location at the same date and time. Everything must be collected with timestamps and geolocation. All time stamps must be certified by a TSA (Time Stamp Authority) in PKI (Public Key Infrastructure) format. If less information could be collected and the e-signature would still count as “advanced”, it would be perfect to simplify the data collection. Actually, we’d like to make the process as easy as possible to both the salesman and the client. That’s why it would be ideal if it could be done through WhatsApp. But for this, enough data should be collected as to confirm the identity of the signer without being necessary for him/her to access his/her email account. 2. The client opens the link and goes to a webpage that contains the text of the document. We collect the time stamp of the access, and the client is obliged to scroll down the whole text before signing. At the end of the text there could be 2 options: either the client finds a place to draw his/her signature directly or he/she must press a button saying "I’ve read the document and wish to sign it". The first option would be preferable, to improve usability. Unless we find it is mandatory to ask for the customer’s permission. It is not necessary to capture the “pen’s” pressure, but if the salesman wants to buy a special e-pen that captures pressure, the signature drawing should show the pressure variation. Then either the customer must press a “Send” button or it sends automatically, making usability easier. The client must immediately receive a copy of the document in his/her email. The salesman will keep a copy of the whole information in our software, and he will be able to print it if needed for a trial or other use. 3. The document is encrypted so that it can be guaranteed that it could not have been modified after signing. The time stamp of the encryption is registered. 4. All the information collected must be sent to our software, because it must be available for printing if the salesman needs it. Some softwares offer the option of editing the document with the client (like Google Docs) before signing it. This would not be the case for every document, but it would be nice to offer this option for some cases. We’d like to maybe redirect them to Google Docs and then, when the document is approved by both, send the text to our app and follow the same steps explained above. We would also like to explore if blockchain could be used to optimize this process. Finally, we need to know the operating costs the app would have after completion. Thanks