Secret phrases that lie at the heart of modern data encryption standards were accidentally forgotten decades ago – but now cryptographers are offering a cash bounty for anyone who can figure them out. While this won’t allow anyone to break these encryption methods, it could solve a long-standing puzzle in the history of cryptography.

“This thing is used everywhere, and it’s an interesting question; what’s the full story? Where did they come from?” says cryptographer Filippo Valsorda. “Let’s help the trust in this important tool of cryptography, and let’s fill out this page of history that got…