The technology disclosed herein provides a proof-of-work key wrapping system that uses integrated key fragments to cryptographically control access to data. An example method may include encrypting a first cryptographic key to produce a wrapped key, wherein the first cryptographic key enables a computing device to access content; determining a plurality of key fragments of a second cryptographic key, wherein the second cryptographic key is for decrypting the wrapped key and at least one of the plurality of key fragments is derived using one of the key fragments as input; selecting a set of cryptographic attributes for deriving the plurality of key fragments, wherein the set of cryptographic attributes are selected in view of a characteristic of the computing device; and providing the wrapped key and the set of cryptographic attributes to the computing device, the set of cryptographic attributes facilitating determination of the second cryptographic key.