not signing screens, and not signing whatever is put in front of you

A local heating firm just came to service the boiler.  This is part of the rented house, so I don't seem to have a choice in supplier.  Having finished the job, they put a blank screen in front of me, and asked me to sign.  The optimistic interpretation of this would be "signing a blank piece of paper means nothing; therefore signing this blank screen means nothing.  My signature is not itself confidential, and by providing it here I do not commit to anything.  At most, the implied meaning of signing a blank sheet for someone who's just done a job in the house is "they visited".

Being conservative about what I sign, I asked, in very bad German, what am I signing here.  At this point he did something on the touchscreen, and there was a picture of an invoice on a sheet of A4 paper.  He continued to hold the device facing himself, and I was unable to read it upside-down and at a large angle and held by another person.  But the decision was already made (and really was just an application of existing policy): I ain't signing no screen.  Especially since you tried to get me to sign a blank screen, only after showing me what I am supposedly signing.  And the point is, of course, that devices can be diddled, so they can attach my signature to arbitrary content, and no one is any the wiser, in a process known as "SBB Signature Fraud" [0].  He tried calling the boss, and got no reply.  I said I'll pay the bill no problem, I just don't sign screens, and even got him to understand, in my bad German, what the issue is.  I did ask if he could print it, but he said no.

[0] <https://wibblement.blogspot.com/2022/03/sbb-signature-fraud.html>

My general requirements for signing documents, and I do not yet apply these without exception, are:

• provide me with two identical copies, on paper: one to keep, and one to sign and give back
• there is a clear reason that a signature should be used in this situation
• I consider signing to be in my interest, and there is, at least implicitly, an answer to "what happens if I don't sign this?"
• I went in to the situation expecting to sign something, and had an opportunity to do any preparation
• the signed content is simple enough, and I understand it fully enough, to sign it without obtaining legal advice on it

Almost no one requesting my signature is able to fulfill the requirement involving two bits of paper.  Presumably, the world is full of people who just go round affixing their signatures to this and that, keeping no records, and then wondering what went wrong.

It may be possible to do electronic signatures, but they look nothing like this.  A system for doing so would have to decide whether an electronic signature is a way of using gadgetry to apply one's hand to a document so as to agree to it, or whether a private cryptographic key can be applied to the document by analogy with applying one's seal (Job 38:14).  The latter type of mechanism is called, in a metaphor that we would have been better off without, since it begs that question: "digital signature" (or cryptographic signature, still a bad name).

Signatures have power.  Look at the obsession of regimes, from gulag-era Soviets to contemporary Merka, with the getting of the signed confession, or the signed "we own you now".  I wonder if lackadaisical signing of whatever is put in front of you, or even whatever is not put in front of you (via a screen), could even be a defence against this, in an EU-cookie-directive-isation (de facto anullment) of all "agreement".  But then we are in a world without contracts, and in any case this is not the approach I have decided to take for now.