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Merritt Fixity Authenticity for Managed Digital Assets

Merritt Fixity Authenticity for Managed Digital Assets. University of California Curation Center California Digital Library April 7, 2011. Fixity. A means for determining whether a digital resource is authentic; in other words, that it conforms to a known (and trusted) state

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Merritt Fixity Authenticity for Managed Digital Assets

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  1. Merritt FixityAuthenticity for Managed Digital Assets University of California Curation Center California Digital Library April 7, 2011

  2. Fixity A means for determining whether a digital resource is authentic; in other words, that it conforms to a known (and trusted) state • A guard against various preservation threats, such as media degradation, software/hardware failure, natural disaster, and inadvertent or malicious human behavior hn, http://www.flickr.com/photos/neumeyer/3729267245/ Pyroclastichawk, http://www.flickr.com/photos/neumeyer/3729267245/

  3. Fixity A means for determining whether a digital resource is authentic; in other words, that it conforms to a known (and trusted) state • Codified as an important element of an OAIS information model in ISO 14721 [http://public.ccsds.org/publications/archive/650x0b1.pdf] • Identified as an important criterion for a TDR in the TRAC audit checklist [http://www.crl.edu/sites/default/files/attachments/pages/trac_0.pdf, B4.4] Timothy Valentine, http://www.flickr.com/photos/el_ramon/4221629185/

  4. Message digests The goal of digital preservation management is to preserve information, but that information is always represented by bits • Bits can be verified for authenticity by comparison of message digests (aka checksums) • Different digest types trade off computational efficiency with cryptographic security • Adler-32, CRC-32 • MD2, MD5 • SHA-1, SHA-256, SHA-384, SHA-512 MarcinWichary, http://www.flickr.com/photos/mwichary/2355783479/

  5. Preservation management Fixity is one component of any pro-active preservation management program • Persistent identifiers • Persistent storage • Fixity • Replication • Characterization • Discovery • Transformation • Annotation

  6. Preservation management Fixity is one component of Merritt’s pro-active preservation management http://merritt.cdlib.org • Persistent identifiers • Persistent storage • Fixity • Replication • Characterization • Discovery • Transformation • Annotation EZID CAN/Pairtree/Dflat/ReDD Fixity Version2 Replication JHOVE2 XTF

  7. Assumptions • Digital resources may be managed in a variety of services and systems • Fixity verification should be performed periodically • If the size of a resource doesn’t match, it is not necessary to verify the checksum • The “known” size and digest value for a resource may change over time Litchfield District Council, http://www.flickr.com/photos/30084068@N08/3813864085/

  8. Features • The unit of verification is the item • Items are represented by URLs • Items are associated with a known size and message digest value, and a status: • unverified, verified, size mismatch, digest mismatch, unavailable • All items are verified periodically at a configurable interval • “Free” link checking Rafael Anderson Gonzalez Mendoza, http://www.flickr.com/photos/andercismo/2349098787/

  9. Features • Verification can be suspended and resumed gracefully • Summary reports are issued after each complete iteration • Items may be associated with one or more contexts, so they can be grouped together in context-sensitive query results Aaron Smith, http://www.flickr.com/photos/theartguy/178700752/

  10. Questions? http://www.flickr.com/photos/thecuriousoysters/4458657148/

  11. Feedback we’d like from you • What is the appropriate periodicity of iteration? • Currently, any fixity violations are reported to UC3 staff, not to owners or curators • Are there use cases in which you would want to receive notification directly? • Are there other kinds of desirable reporting of results? MattiMattila, http://www.flickr.com/photos/mattimattila/4863055461/

  12. Feedback we’d like from you • Do you anticipate using this service to verify non-Merritt content? Are you interested in deploying the service locally for this purpose? • How often do anticipate your content changing? http://www.flickr.com/photos/bala_/1420171699/

  13. For more information UC Curation Center http://www.cdlib.org/uc3 uc3@ucop.edu Merritt repository http://merritt.cdlib.org/ UC3 Stephen Abrams Margaret Low Lisa Colvin David Loy Patricia Cruse Mark Reyes Scott Fisher Tracy Seneca Alex Genadinik Joan Starr Erik Hetzner Marisa Strong Greg Janée Perry Willett John Kunze

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