In a remarkable exchange that occurred after Laszlo Hanyecz shared his GPU miner code with Satoshi, Satoshi reciprocated by sharing his own independently developed GPU mining code. This revelation showed that Satoshi had been working on GPU mining before Hanyecz’s public announcement — not to mine coins, but as a contingency plan to defend the network against potential 51% attacks.
As Hanyecz later recounted:
And he actually shared with me his version of it. So even though it wasn’t in Bitcoin, he did have GPU mining code and he said he was just keeping it ready in case he had to defend the network with it.
Satoshi had developed several versions of the GPU mining algorithm but deliberately chose not to include it in the public Bitcoin software. His strategic reasoning was twofold: he wanted to keep GPU mining capability as a defensive weapon against potential attackers, and he did not want to prematurely increase network difficulty, which would have discouraged ordinary CPU miners from participating.
Hanyecz noted that his own GPU code actually performed better than Satoshi’s version, but that Satoshi had intentionally avoided optimizing it:
And I got the feeling, that part of it was that he didn’t want to prematurely optimize it because he didn’t want to run up the difficulty on the network.
This exchange reveals a fascinating aspect of Satoshi’s strategic thinking: he was simultaneously discouraging public GPU mining to protect accessibility while privately maintaining GPU mining capability as insurance against adversarial attacks. It demonstrates that Satoshi had thought deeply about potential attack vectors and had prepared defensive measures well in advance.
Source: Based on Laszlo Hanyecz’s public statements in interviews with Cointelegraph and other outlets. The full private email correspondence has not been publicly released, but Hanyecz has shared these details in multiple interviews.