The only difference is the absence of the specific envelope with the separate password used for this mutual purpose, but that seems a little cumbersome I think and doesn’t really add anything. As you write – it’s still a case of mutual trust.
I think what Sven was hoping to achieve is a method of distributing a file that would be inaccessible until a sealed envelope was opened.
It’s still an issue of trust because there’s nothing to stop his friend opening the envelope but at least opening the envelope would be detectable, if signed and taped.
Opening the file shared using key-sharing would be undetectable and I can only think that this was what Sven hoped to achieve when he said:
<p style=”text-align: right;”>“Please note that – as far as I understand – the key sharing method in the premium version does not help, as part of our scheme was the ability to keep the information securely deposited until the other party opened the password/key envelope. (Please correct me if I am wrong.)”</p>