Where did the 15 promises of the Rosary come from?

According to tradition, the Blessed Mother gave these 15 promises to St. Dominic and Blessed Alan de la Roche.

These promises are promoted by the Rosary Confraternity, an association of people around the world who strive to pray 15 decades of the rosary each week (the Joyful, Sorrowful, and Glorious Mysteries). Also, they encourage (but do not require) the members to pray the Luminous Mysteries. There are certain plenary and partial indulgences associated with being part of the Confraternity. Finally, since the members of the Confraternity pray for the intentions of the rest of the society, this means that each member receives a share of hundreds of thousands of prayers every day.