Signing Documents with Blockchain and IPFS

Question

For my little project I need help and if it's possible. The project is about signing documents using blockchain and IPFS. I try to create a DApp with following features:

1. Signer has to LogIn
2. After LogIn has been successful you can upload a document.
3. You can sign uploaded document.
4. DocumentHash is generated. DocumentHash should be stored on Ethereum Blockchain. Signed document is stored on IPFS.

Now I am trying to write my smart contract. The signature should be created as a object. So a signature is made of Name and actual time. This means signature should be created out of the information of the LogIn-process (first Name, last Name, SignerID (is unique, like password).

Is this possible with a Smart Contract? I don't know what to do so I don't know how to create this Signature within a Smart Contract and put the signature to the document. Then I know what to do with hashing the whole document and push it to IPFS... Thank you!

Answer 1

The good news is: All your problems are already solved. The bad news (for you): Without blockchain.

I'm also not smart which this is smart in any way, but typically that's the way you want to go:

1. Take a hash over all the documents you want to sign

2. Looking at the public key cryptography (https://en.wikipedia.org/wiki/Public-key_cryptography), sign the hash with your private key. Signing the hash will proof the authenticy later.

3. Put the hash in any blockchain you want

By the way: There are a lot of Certificate Authorities that would also sign your hash from 2) without any high engery-consuming smart and inefficient blockchain stuff. Just saying.