Remember when Hans Reiser successfully destroyed all definitive forensic evidence of his murder of his ex and then got convicted anyway because nobody believed he was innocent then traded handing over her body for a lighter sentence?
Even if you could theoretically create a mathematically plausible doubt it doesn't matter if a judge and or jury doesn't believe it.
Also both Google and the recipient can attest the message hit the server prior to the key being published. You MAY be in a position where your email provider is in a different jurisdiction and not inclined to cooperate but if bob the witness already gave up your message won't he give up the timeline breaking any hope of repudiation?
So all hope of an upside is basically a pipe dream. Lets talk about the downside you can now sign crap with Googles already published key and lie about the timeline. You can have "experts" go on TV and lie about authentication. Since most people know less than nothing on the topic it sounds on its face believable.
Hans Reiser was convicted because there was much circumstantial evidence, he insisted to testify, his explanations were unlikely, and jurors thought he acted guilty. He said he threw away his car's passenger seat after his ex wife disappeared so he could sleep in the car. And removed the rear carpet to make a futon. But threw it away. And so on.
Criminal cases are not the only scenarios when authentication is relevant. Most email providers would not authenticate a message without a court order probably. And they may or may not retain sufficient information. A recipient whose messages were hacked would not want to authenticate the messages usually. A recipient who would benefit from disclosing a message the sender didn't want disclosed would benefit from forging a message usually.
Is it now not possible for people to go on TV and lie to people who know less than nothing about a topic?
Its easier if we can go say something half truthful like your blood was found at the scene even if the scene was a kitchen where you had regularly cooked and the blood was of indeterminate age than to make something up from whole cloth. The later is also legally actionable while the former may well not be.
The jurors heard where blood matching Nina Reiser's DNA was found. It was the entrance of the house where Hans lived after they separated and a sleeping bag cover in his car. Not the kitchen. They heard his claim she cooked there. They heard a witness admit bad technique meant the sample inside the house could have been Hans's blood mixed with other DNA from Nina. Saying the age couldn't be determined didn't help the prosecution. Reports at the time said it was the 1 piece of evidence the defense made reasonably doubtful.
Even if you could theoretically create a mathematically plausible doubt it doesn't matter if a judge and or jury doesn't believe it.
Also both Google and the recipient can attest the message hit the server prior to the key being published. You MAY be in a position where your email provider is in a different jurisdiction and not inclined to cooperate but if bob the witness already gave up your message won't he give up the timeline breaking any hope of repudiation?
So all hope of an upside is basically a pipe dream. Lets talk about the downside you can now sign crap with Googles already published key and lie about the timeline. You can have "experts" go on TV and lie about authentication. Since most people know less than nothing on the topic it sounds on its face believable.