Gemalto, the world’s biggest manufacturer of SIM cards—the tiny plastic-encased chips that allow mobile-phone handsets to connect to networks—today responded to claims that it had been hacked by the American and British governments’ cyber-spies. The hacking allegation was the latest fallout from the trove of documents taken from America’s National Security Agency by Edward Snowden, a former contractor. The documents outlined an apparently successful operation to steal millions of encryption keys, one of which is contained in each SIM card. Possessing those keys would let spies to listen in on mobile-phone calls, which are encrypted by default. Today Gemalto said that although its office networks were breached, there was no “massive theft” of encryption keys, and any keys stolen from elsewhere would have allowed access only to old-fashioned 2G networks, not modern 3G or 4G ones. Its shares, which had fallen by 8% when the news emerged, rebounded.