Outages have been compounded by cryptocurrency mining, which uses banks of high-powered computers. Cities across Iran have been cloaked in thick layers of toxic smog and darkened by blackouts, as the alleged use of low-quality fuel and power-sucking cryptocurrency mining deepen the country’s hardships. Tehran’s Hamshahri newspaper, the country’s most-read daily, ran the headline, “20 Days Living in Smoke,” on Wednesday over a photo of the capital covered in smog. Power plants have been forced to switch to burning low-grade fuel oils to generate electricity because high levels of domestic consumption have led to natural-gas shortages, the semi-official Iranian Students’ News Agency reported. Oil Minister Bijan Namdar Zanganeh denied earlier this week that any of Iran’s power stations are us...