From an interview with Neal Stephenson:
Hooke, for example, when he figured out how arches work, published it as an anagram. He condensed the idea into this pithy statement: “The ideal form of an arch is the form of a chain hanging, flipped upside down.” Then he scrambled the letters to make an anagram and published it. That way, he wasn’t giving away the secret, but if somebody came along a few years later and claimed that they’d invented it, he could just unscramble what he’d published. He was establishing precedence.
How long until someone publishes a paper on the arXiv which is just noise and then, after some major result appears, says “No, I did this a long time ago, and here is the key which unscrambles my paper?