Desperate to find a new supply of protective face masks, executives at an American health care services company last month began poring over videos shot inside Chinese factories — and listening closely for gibberish.

Nonsensical sayings that accompanied the videos were a kind of code — a requirement that Premier Inc., the prospective buyers, insisted on to ensure authenticity.

"It seems ridiculous,” said Soumi Saha, a senior director at Premier, which buys medical supplies for more than 4,000 U.S. hospitals and health systems. "But we’d have to ask folks at the manufacturing facilities to say ridiculous statements that you wouldn’t say in conversation to know that the videos are legitimate — not scams.”