This code shows how you can extract a ECDSA private key from two messages signed with the same Nonce value. Every signature requires a unique integer plus the private key to avoid this attack.
In 2011, Sony's private key was revealed by this attack. This allowed anyone with the private key to sign messages and make them appear to be from Sony. Attackers used this to sign binaries, allowing arbitary code to be exectued on Playstation 3 consoles.
Tested on python version 3.6.2,
ecdsa 0.13,
Install command: "pip install ecdsa"