There are two kinds of Hasso--Fuho Hasso (eight forefathers from Dainichinyorai to Kukai) and Denji Hasso (eight forefathers who appeared during the period of history in which the teachings of the Shingon sect had been introduced to Japan)--and Kukai described the origin of Shingon Mikkyo, the biographies of the seven forefathers of Fuho and seven forefathers of Denji (seven forefathers of Fuso and Denji Hasso except Kobo-daishi) and lineage of Fuho in his works 'Himitsu Mandala Kyo Fuho Den (秘密曼荼羅教付法伝)' and 'Shingon Fuho Den (真言付法伝).'
付法（ふほう）の八祖と伝持（でんじ）の八祖の二つがあり、空海は著作「秘密曼荼羅教付法伝」・「真言付法伝」で、真言密教の起源と付法の七祖・伝持の七祖（付法・伝持の八祖の内、弘法大師を除く七祖）の伝記や付法の系譜を記している。