Iron Age Scottish written language?

DiscoveryNews reports:

The ancestors of modern Scottish people left behind mysterious, carved stones that new research has just determined contain the written language of the Picts, an Iron Age society that existed in Scotland from 300 to 843.

The highly stylized rock engravings, found on what are known as the Pictish Stones, had once been thought to be rock art or tied to heraldry. The new study, published in the Proceedings of the Royal Society A, instead concludes that the engravings represent the long lost language of the Picts, a confederation of Celtic tribes that lived in modern-day eastern and northern Scotland.

The paper ("Pictish symbols revealed as a written language through application of Shannon entropy") is open access.