Researchers at Ben-Gurion University of the Negev in Israel have successfully transmitted private keys out of digital wallets that were physically separated from the internet and other networks, Ars Technica reported Monday. The news is likely to alarm cryptocurrency holders who think their keys are safe if their devices are offline. The researchers’ attacks make an important assumption — that a device has already been infected by malware. Professor Mordechai Guri and colleagues used a variety of techniques, including electromagnetic emissions from USB devices and radio signals from a computer’s video card, to extract data from “cold wallets,” which are stored on devices not connected to the internet. They found that the most effective techniques require only seconds to pull a 256-bit bitcoin (BTC) key from a wallet running on an infected computer. Read more here.