Alison Flood in The Guardian:
The mysterious jötunvillur code, which dates to 12th or 13th-century Scandinavia, has been unravelled by K Jonas Nordby from the University of Oslo, after he studied a 13th-century stick on which two men, Sigurd and Lavrans, had carved their name in both code and in standard runes. The jötunvillur code is found on only nine inscriptions, from different parts of Scandinavia, and has never been interpreted before.
“The thing that solved it for me was seeing these two old Norse names, Sigurd and Lavrans, and after each of them was this combination of runes which made no sense,” said Nordby, who is writing his doctorate on cryptography in runic inscriptions from the Viking Age and the Scandinavian Middle Ages. He then realised, he continued, that in jötunvillur, the rune sign is swapped for the last sound in the rune's name, so for example the “m” rune, maðr, would be written as the rune for “r”.
“I thought 'wow, this is the system, this is the solution, now we can read this text,” said Nordby. But the code turned out to be extremely confusing, because many runes end in the same sound, “so you have to decide which one to choose”.
More here.