Re: Why has my newly created Bitcoin address already been used?
here is a better thought: instead of using websites or even their source code you can use a popular wallet to create a paper wallet. wallets such as bitcoin core or electrum.
just download them, verify their signature and then go offline on an airgapped machine. run the wallet and create a new key or better yet create a mnemonic with an HD wallet such as electrum. then write that down on a piece of paper as your paper wallet.
if you like the design that those sites offer you can always find their source code (or even through the HTML in the site that is open) and save the picture which is usually a jpg file and print your key on that.
+1. just download them, verify their signature and then go offline on an airgapped machine. run the wallet and create a new key or better yet create a mnemonic with an HD wallet such as electrum. then write that down on a piece of paper as your paper wallet.
if you like the design that those sites offer you can always find their source code (or even through the HTML in the site that is open) and save the picture which is usually a jpg file and print your key on that.
I never felt secure when using paper wallets generated by a website.If you are not new to PCs, there is one more thing you can do: securely flash Tails (a Linux distro) on a 8GB+ USB stick and use Electrum over there offline (or online, your choice).
Just make sure you store the seed correctly and you should be good to go. Once you shut down or reboot your PC, everything will be reset and any new change/file will be deleted.
Plug out your Ethernet cable, optional step: physically disconnect all hard drives from your PC, insert the bootable USB, boot Tails and there you have an offline, airgapped PC to safely use Electrum with. And as far as I know, you could use Tails online with Electrum - as long as you've verified the flashed ISO signatures correctly, risks should be minimum.
The advantage of this is that afterwards you can just shut down your PC, plug out the USB stick and use it again whenever you like. Moreover, your bootable Tails will run on Tor all the time.