SPEED BOUNTY · POLLARD'S KANGAROO

Catch the wild kangaroo

When a key's public key is known and its range is small, Kangaroo finds it in about √W steps instead of W. A tame herd hops from known points, a wild herd hops from the target; when they land on the same marked spot, the key falls out. This only works for revealed public keys — not Puzzle #71.