Microsoft Technology Licensing, LLC

Simon Wai Leong Leet

Sarjana Sheth

Patrick T O'Brien, Jr

Jack R Davis

An archive of an object set may include various security features that enable a detection of alterations of the contents of the objects. However, the security measures of an archive may fail to detect an inadvertent or intentional alteration of the structure of the object set, including the addition of new objects, changes to the metadata (e.g., the name, position within the object set, and location and size within the archive) of respective objects of the object set, and the deletion of directory entries for the objects. Therefore, an archive may be generated with verifiers (e.g., hashcodes) calculated not only for the contents of objects, but for the directory of the archive, and may be included in the signature of the archive. This verification may extend the detecting of alteration of the archive to include the structure of the archive as well as the contents of the objects contained therein.

Protecting archive structure with directory verifiers

The objects of an archive may be verified with a cryptographic signature stored in the archive. However, when an object is extracted, the authentication involves re-authenticating the entire archive, re-extracting the object, and comparing the extracted object with the current object, which is inefficient or unachievable if the archive is unavailable. Instead, the archive may include a block map signed with the signature and comprising hashcodes for respective blocks of the objects of the archive. When an object is extracted, the signature and block map may also be extracted and stored as objects outside of the archive. The extracted signature and block map may later be verified by authenticating the signature, verifying the block map with the signature, and matching the hashcodes of the block map with those of the blocks of the extracted objects, thus enabling a more efficient and portable verification of extracted object with extracted authentication credentials.

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Simon Wai Leong Leet