Embodiments of the present invention provide a key insulation method and device. The key insulation method includes: randomly selecting a first parameter s from Z*q, acquiring a helper initial key from a helper, and generating an initial user private key according to the first parameter s, a preset first cryptographic hash function H1, and the helper initial key; and acquiring a helper updated key for a time segment i from the helper, and updating a user private key for a time segment j according to the helper updated key for the time segment i to obtain a user private key for the time segment i. According to the key insulation method and device provided by the embodiments, in a process of generating an initial key and a process of updating a key, lifecycle is not involved, which improves flexibility of a key system.