Core Private keys

[kuk]

Hallo Guys

i'm reading a few things about importing/exporting  private keys and core and on some sites there are warning like this

"Before reading this page, users should note that messing with ECDSA private keys is very dangerous and can result in losing bitcoins, even long after the import. It is recommended that outside of self-generated vanity addresses, users should never import (or export) private keys."

Whats that about an wheres the danger if i export the key in core and Import it to another wallet. Isnt it so that importing and exporting a private key gives us the advantage of beeing in full controll of our bitcoins so that this should be a good thing in core not sth i should worry about!? Altough in most cases i would just send it to another adress without exporting/importing the key but in case of August 1. and bitcoin cash i probably have to export my core key and import it to f.e abc wallet

Big thanks in advance for every answer

[achow101]

Exporting and Importing private keys makes the private key exposed to many more things. When you are using Bitcoin Core, you are already in control of your private keys. The keys are protected by the software. If your wallet is encrypted (and it should be), then the unencrypted keys only exist in the software's allocated memory for a short period of time. However, as soon as you decide to export your private keys to import elsewhere, you are exposing your private keys to many many more things. They are now exposed to your video card and its drivers. It becomes exposed to your monitor, to your clipboard, to other software which may not have the same protection that Core provides, etc. Any one of these things, if infected with malware or if it has a vulnerability, could reveal your private keys to an attacker. Furthermore, you are now also vulnerable to shoulder surfers, or if you are in a public place, security cameras that can see your screen. Since exporting your private keys exposes it to so many more things that could have vulnerabilities, it is recommended for you to not handle them directly and let the software do it. This means that you shouldn't be exporting and importing keys.

Furthermore, exporting and importing keys implies that you will have multiple wallet instances with the same private keys. This is also inadvisable as having one of those instances compromised will compromise all of your private keys and all of your Bitcoin. That means that an attacker has more things he can try attacking. Doing that is also inadvisable since transactions that you make from one wallet instance may not necessarily appear on another wallet instance and result in you accidentally making double spends.

If you have a Bitcoin Core wallet and want to spend your BCC after the fork, you don't need to handle the private keys directly by importing and exporting them. Rather you can just install Bitcoin ABC and use your wallet file with Bitcoin ABC and spend your Bitcoin from there. Bitcoin ABC uses the same wallet format as Bitcoin Core as it is a fork of Bitcoin Core. The wallet.dat files are compatible with both clients.

[kuk]

thank you for your answer