The Ledger Nano is a smartcard based hardware wallet. Private keys are generated and signed offline in the smartcard’s secure environment. The Nano is setup using the Ledger Chrome Application. A random 24-word seed is generated upon setup and backed offline by writing it down on a piece of paper. In case of theft, damage or loss, the entire wallet can be recreated with the seed. A user selected PIN code is also assigned to the device to protect against physical theft or hacking.
Various potential attacks on the bitcoin network and its use as a payment system, real or theoretical, have been considered. The bitcoin protocol includes several features that protect it against some of those attacks, such as unauthorized spending, double spending, forging bitcoins, and tampering with the blockchain. Other attacks, such as theft of private keys, require due care by users.
A backdoor like Antbleed, if utilized, would give an ASIC manufacturer the power to effectively silence miners who support a version of the Bitcoin protocol that it doesn’t agree with. For instance, Bitmain could have flipped a switch and shut down the entire facility in Ordos if the company found itself in disagreement with the other shareholders.
The receiver of the first bitcoin transaction was cypherpunk Hal Finney, who created the first reusable proof-of-work system (RPOW) in 2004. Finney downloaded the bitcoin software on its release date, and on 12 January 2009 received ten bitcoins from Nakamoto. Other early cypherpunk supporters were creators of bitcoin predecessors: Wei Dai, creator of b-money, and Nick Szabo, creator of bit gold. In 2010, the first known commercial transaction using bitcoin occurred when programmer Laszlo Hanyecz bought two Papa John's pizzas for 10,000 bitcoin.