Pasture Node State Specification

Pasture [5] is a secure messaging and logging library that enables secure off-line data access on untrusted user devices by leveraging commodity trusted hardware. Pasture does not trust the application, OS, or hypervisor and even admits hardware snooping attacks, while providing two important safety properties: access-undeniability (a user cannot deny any off-line data access obtained by his device without failing an audit) and verifiable-revocation (a user who generates a verifiable proof of revocation of unaccessed data can never access that data in the future). Each node running Pasture uses its Trusted Platform Module to protect and log access to encryption keys that shield the data. Permanently forfeiting the ability to access an unused decryption key is the basis of revocation.