Hardware Back Doors

Another potential “back door” into the Bitcoin network could be via the mining hardware. It is theoretically possible that Bitmain or one of the other large manufacturers of Bitcoin mining hardware could have included circuitry in its ASICs that allows someone to effectively flip a switch and take over the hardware remotely via an Internet connection.

This sort of risk appears quite unlikely due to scanning technology that allows scrutiny of the circuitry of the ASICs used to mine Bitcoin. Bitcoin ASICs are much simpler than motherboards for personal computers and commonly used data center servers. ASICs are designed solely to perform the SHA-256 hash calculation, which is far less complex than the functions that most computers perform. If anyone were to examine mining equipment and discover a back door, the manufacturer’s future equipment sales would likely go to zero instantly. Nobody wants to buy mining equipment that can be instantly deactivated by the manufacturer! Since the Bitcoin ASIC manufacturing business is probably worth billions of dollars as of this writing, it appears extremely unlikely that the major hardware manufacturers would risk their profits by including back doors in their products.

Notwithstanding that it is already low, this hardware back door risk will probably reduce further over time as the ASIC manufacturing business becomes larger (and therefore more equity value is at stake). The risk will also probably reduce as the rate of improvement in ASIC circuitry slows. The industry has already reached seven-nanometer spacing on its chips,¹⁵² which is approaching the maximum transistor density possible before quantum effects lead to interference. Such effects limit further miniaturization based on existing two-dimensional silicon-based chip architecture. Three-dimensional (stacked) chip architecture will probably emerge eventually, but that could take years.