ACE: A Software Tool to Ensure the Integrity of Digital Archives Principal Investigator: Joseph JaJa Graduate Student: Sangchul Song Lead Programmer: Michael Smorul University of Maryland, College Park

September 2009 GeoMapp 2 Using Hashes to Monitor Files Strong hashes can assert a file has not changed How to manage millions of hashes? How do you prove the hash value hasn’t changed? How do you prove a hash value was issued at a given time?

September 2009 GeoMapp 3 Audit Control Environment (ACE) Solves the problem of storing and verifying hashes. Secures hashes by issuing token for each file/hash to me monitored. Tokens contain a cryptographic proof that allows for 3 rd party auditing. One number stored externally is used to audit tokens and hashes.

September 2009 GeoMapp 4 Hash Authentication Hash 1Hash 6Hash 5Hash 3Hash 4Hash 2 Intermediate Hash Value Previous Round Hash CSI (one hash value) Challenge Hash IHV Gather Hashes During RoundCreate Merkel Tree For Supplied HashesLink to previous round Generate proof for hash

September 2009 GeoMapp 5 Token Sample SHA SHA-256 /SRB3_2_1f.tar T11:03: e869e2ce41ede3ceb3af50f8aa b3e67055b5b3d2787e2c294a95a869 6a d7b4ff660d499416fd45a20dde161eb68e59fedc0f58208ad86cf a6a d24e99435e817511eeb89ddc03afbc6a30f23e404847cc06 1aeaf2d76976cf9759b0d63bc7acdf9c6df68875bfc9bcc0e22c19401aab0133

September 2009 GeoMapp 6 How to scale? Two layers of Merkel tree 1.Short rounds(seconds), that generate Cryptographic Summary Information(CSI). 2.Each successive round includes previous CSI 3.Second, daily rounds comprised of all CSI’s for previous day. Daily tree root, called Witness can validate all CSI’s for a day. –Only 365/year generated. Very manageable! Two components, an Integrity Management Service(IMS), and Audit Manager(AM) were developed.

September 2009 GeoMapp 7 Components Integrity Management Service (remote) –Runs all hash aggregation, round generation, witness publication. –Stores CSI values –Generate proofs from CSI to witness –ims.umiacs.umd.edu Audit Manager (local) –Monitors local files –Determines audit policy –One or more per archive –Locally stores hashes and tokens

September 2009 GeoMapp 8 ACE – System Architecture

September 2009 GeoMapp 9 ACE Audit  Audit Local Files: Audit Manager periodically scans all files and compares stored digests with computed digests.  Assume valid hashes in database  Audit Local Manager: Manager computes round summary for each digest using that digest and its token. This is compared to value stored on the IMS.  Assume IMS returns valid summary information, do not trust hashes in database  IMS Audit: Round summaries are used to compute witness values. These are compared with offsite witness values.  Do not trust IMS, force IMS to prove its CSIs link to a witness

September 2009 GeoMapp 10 Audit Manager Downloadable, one or more per archive Monitors local files Simple Requirements –Java 1.6+ –Tomcat –MySQL Managed by archivist/librarian after install Monitor multiple collections on different architectures Hides all the complexity you just saw!

September 2009 GeoMapp 11 Performance Audit Manager (1.1beta3) 1.25 million false hashes (no bytes read) –Registration: 3h, 6m (112 files/s) –Audit: 1h, 15m (277 files/s) 1.25 million false data files (1.25Tb data) –Registration: 5h, 7m (67.8 files/s, 67.8MBytes/s) –Audit: 4h, 30m (77.2 files/s, 77.2MBytes/s) In practice, bottleneck tends to occur at archival resource, not AM. Chronopolis –5.5m files, over 20Tb in size

September 2009 GeoMapp 12 Future Directions Statistical sampling –Low-rate auditing, probability of error detection Cloud auditing –Data transfer costs $$$ –Is the cloud lying? Additional Storage Support –Web, ftp, smb

September 2009 GeoMapp 13 ACE Summary Third-party auditable Cryptographically rigorous yet cost-effective Scalable, High Performance Current Efforts –Provide public IMS –Create simple audit manager for local use