Square has designed custom ASICs before. One of the older Square readers did crypto just based on power from the phone's 3.5mm headphone jack, so they had to ge

Square has designed custom ASICs before. One of the older Square readers did crypto just based on power from the phone's 3.5mm headphone jack, so they had to get creative. Then in 2015 they bought Kili, a Canadian company whose entire business was a custom payments ASIC [1]. I didn't work on hardware when I was at Square, but I expect many members of the Kili team contributed to this effort. [1]: https://techcrunch.com/2015/03/11/square-buys-kili-technology-for-payment-hardware-hq-to-become-toronto-office/ https://techcrunch.com/2015/03/11/square-buys-kili-technolog...