@northerner can't really tell, maybe it's part if the utility's initial setup

@northerner The creator of the file would need to sign it somehow with their own private key first, no?

They would then provide the paired public key for public download, which you could use for verification.

If the creator encrypts something with their private key, when you decrypt it with the public key, you know that the message came from the owner because only the owner has private key.

If you encrypt something with public key, then only the owner of the private key can read it

I think

But you shouldn't need your own key to verify something signed by someone else

right?

Yeah, creating your own key doesn't make sense. You'd have to use a key provided by the author of the file

Isn't that the way PGP works, you need to sign a key (with your own) to trust it. So you do need your own key pair before you can use anyone else's key?

no?

author creates file, and verification file/data using (file + private key)

I just tried deleting my own key and now when I try to verify a file with the authors key, I get the error message 'The used key is not certified by you or any trusted person.'

you can use the latter to verify the former using the public key

But PGP needs to know you trust the public key you got, and that's why you sign it with your own. Or no?

you don't need a key to verify a file signed with a private key

if you're using pgp, it might ask you "do you trust this public key"

it's been a while since I did anything like that

When download a file over a secure connection like HTTPS or SFTP does it really add integrity to use PGP to verify the file with the public key?

@northerner SSL (the encryption technology used by HTTPS and SFTP) ensures that the data cannot be viewed or modified while it is traveling from the server to your computer.

So, you can be safe in knowing that the file wasn't modified in transit, but if the server itself was hosting a comprised file, then SSL will not protect you from that

SSL uses public key encryption to safely transmit a one-way encryption key to your computer. That key is then used by your computer and the server to encrypt all communication.

@Michael so then where do people usually get the public key from? If the server hosting the file was compromised then it would seem easy to replace the public key?

I get that ideally the key fingerprint is given to the person over the phone or something, but I'm wondering about public websites like KeePass

Your browser automatically retrieves it during the connection process. It also checks to see if the public key validates against a certificate authority, and if it doesn't, it shows you a warning

You can see which certificate authority the site uses by clicking the Lock icon in the address bar.

I am talking about PGP and downloading the public key to verify the downloaded file wasn't tampered with.

If KeePass's web server was compromised then the attackers could post their own public key on the website and then regenerate the signatures using their own private key.

Not sure what the point of posting those signatures is tbh

The hashes ensure that the file wasn't corrupted during download

OK that's what I was wondering.

Also what do people call the file ending in .asc ?

@Michael isn't the point that the the signatures can't be generated except with the private key of the dev

so if the website hosting the <whatever> (software, intel, grandma's famous cookie recipe) is compromised, Ms McBlackhat can replace the <whatever> with her version of compromised software/intel/recipe

but she would have to replace the verification / signing info too

@bertieb Yes but if an attacker gains access to the web server, then the attacker could just regenerate the signatures with their own private key.

@Michael which she can only do with a different private key, not the one that belongs to Mr Dev Eloper

which is why you need to check what the signing info is telling you

unless they also somehow get hold of the receiving person's mail account or manage to confuse you into using a different address, that only gets that person to receive a message they can't decrypt

@bertieb Right. And then she posts her own public key on the website and acts like it's the developer's public key.

she can't put up a file which says, essentially, "the hash of <this file> + <Dev Eloper's> private key" is XYZ

@Michael well yeah, if you keep all your eggs in one basket...

but ideally you can verify a key OOB

How else are you supposed to get Mr Dev Eloper's public key?

SE sites are responding very slowly again... new DoS attack?

(trusted keyserver, by phone, whatever)

but yes, if the only storage of the public key is the same as the thing the public key is verifying, it does not work well

I guess getting the public key from another server than the one hosting the download helps confirm the authenticity - it's less that two servers on separate networks are compromised.

But that's not what's happening with websites like KeePass's

it also semi-suffices to describe the pubkey else

post pubkey on website, then elsewhere (twitter, reddit, etc) say "my pubkey ends in 'DEADBEEF'"

Mine is tattooed on my forehead

Are encryption keys longer than 40 bits still considered 'munitions'? :x

geekytattoos.com/illegal-tattoos-rsa-tattoos

@Michael I imagine ending up in prison with a PGP tattoo on your forehead will pretty much make you anyone's bitch

0_o

@MiG Ha that's cool

@Michael they have been having trouble. Not sure what yet