In Poland you can use "podpis zaufany" to sign a file, which also records the date of signing. The only thing you need is a bank account which was verified usin

In Poland you can use "podpis zaufany" to sign a file, which also records the date of signing. The only thing you need is a bank account which was verified using your physical ID. The best UX, I think, is with PDF files - others are encapsulated in an XML Base64 container. Everyone can verify a signature with no account necessary.