Kalcifer

This one actually isn't so bad. If a person opts out of their edit history being shown, at least this would be a sort of red flag for the reader that should trigger skepticism in the content's trustworthiness. That being said, it would still be inferior to having a mandatory edit history.

Editing a post may be to remove the password or email address you accidentally copy pasted in, or removing some potentially doxxing information, or one of many reasons you want that content gone.

Why not just delete the post, and then make a new one with the correct information?

Github has edit history, but it also allows users to delete revisions so it seems your main concern would not be resolved by this implementation.

If this were to be allowed, the edit history would then be pointless.

And as you point out, there is already a message that says the post was edited and what time.

That is the only information that is provided. One is unable to find out what was changed.

Nah, never liked the feature, wouldn’t appreciate it here.

Would you mind elaborating on why you feel that way?

Side note, external images can be embedded in markdown like this:

![alt description](https://example.com/cool-image.png)

Thank you for that info! I'll update my post.

Your are absolutely right. I guess I had accidentally copied the wrong link. Thank you for letting me know! I have now updated my post.

Post a link to a channel of 1k users and 1k users send a request to the website, instead of only the server once?

That would only happen if the URL is generated on the recipients side. What Signal does, for example, is it generates the preview on senders side, and sends the preview with the URL, so the preview is only generated once.

/edit: From a privacy standpoint I’d really trust my chat server provider over random websites. So I definitely don’t see how it’s a terrible choice for these two reasons.

What do you mean? How would "random websites" come into play?

That being said, if you’re concerned, disabling previews is the answer.

Thankfully, they are disabled by default.

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OP can edit comment, sign with a different key and claim his comment was edited by the admins.

Dang, that is a scenario that I hadn't considered. I'm not sure that there's anything that can be done about it.

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This is indeed an obstacle in practicality. You are absolutely right in that any channel under control by the admin could be used as a means to orchestrate a MITM attack and replace my public key with theirs. The only way for this to work is for me to personally provide my public key in a separate, and secure channel like Matrix.

I would like to emphasize that this is all just an experiment for my own interest. I would certainly not recommend what I am doing to anyone else.

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Using a bot to generate a URL preview is an interesting workaround.

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Can’t the admins just edit it and sign with a new key?

Of course, but if the signature were to change, it would no longer match the public key.

Either way there won’t be a way to know for sure who edited the comment

The goal is only to know if the OP edited it or not. It doesn't really matter who edited it if it wasn't the OP. The only important information would be that it wasn't the OP.

but well they can just tell you that.

Verifying with the user's public key accomplishes the same, and is independent of a direct audit from the user.

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I certainly could link my server into play as well just to keep an always online device in the mix

Yep! That should work perfectly fine.

What is this post signature [...] Also, what is the purpose?

I'm testing out some ideas that I've had for my posts -- the signature and the edit history. They are a result of the current status of the following two issues on GitHub:

• Add the ability to view an edit history for posts
• Sign a user's posts and comments with a private key that only the user possesses, so that server admins are unable to secretly modify a user's content

Recently (as of 2023-10-02T03:28Z), one of the maintainers/developers for Lemmy closed those two issues with either little, or no rationale. I personally think that they are good features. Since it appears that those features are not going to be seamlessly added to Lemmy, I'm trying to see if it is practical to manually add them to posts.

Regarding the edit history: The purpose of an edit history is to solve the issue of people not knowing what changed in a post when it was edited. The main issue with a user-created, and maintained edit history, however, is its inherent the lack of trust. Its existence increases transparency, but you still have to trust that the user hasn't lied about what is in the diff. The implementation would be to have the server generate it, but, unfortunately, the dev has removed that possibility for the time being.

Regarding the signature: The purpose of the signature was a means to ensure censorship resilience from the admins of an instance. As it currently stands, any admin can freely edit the content of a user's posts, or comments with no one being the wiser. A signature would provide a sort of check against this. If a user signs a post with their own private key, then, by verifying the post's signature with the user's public key, one can be certain that that user was the one that wrote it, and not a server admin, or any other external entity. But, again, this feature has been blocked on GitHub.

The long, and short of it is this is me trying to protest what I think are silly decisions made by the devs of Lemmy.

how does one use it and create one for their own post?

The way that I am currently doing it is I take the raw content of the post, or comment (the body, and it's formatting, including the edits, if they exist, and excluding the signature code block), generate a SHA-256 hash of it, and sign the hash using RSA-2048. For example to sign one's post's content, the following could be done:

1. Put the raw post content into a file, post-content.txt.
2. Generate an RSA-2048 private key, and output it to a file, private-key.pem:

openssl genrsa -out private-key.pem 2048

3. Generate the public key, and put it in a file, public-key.pem:

openssl rsa -in private-key.pem -pubout public-key.pem

4. Hash, and sign the content of the post, then output the signature to a file, post-content.sig:

openssl dgst -sha256 -sign private-key.pem -out  post-content.sig post.txt

5. To then be able to paste the signature as text, it must be base64-encoded:

openssl base64 -in post-content.sig -out post-content.sig.b64

If you would like to verify your signature, you could then do:

openssl dgst -sha256 -verify public-key.pem -signature post-content.sig post.txt

If the signature is correct, then it will return Verified OK

There likely exists other, simpler methods of going about this, but this method is functional.

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Neat idea! Although, it would probably be more practical to use a centralized model since if one peer is offline, then the syncing would not occur. That is, if my assumption is correct that you are thinking of directly syncing between 2 devices.