Audit Control Audit Control EnvironmentEnvironment

Mike SmorulUMIACS

Issues surrounding asserting Issues surrounding asserting integrityintegrity

• Threats to Integrity of Digital Archives– Hardware/media degradation– Hardware/software malfunction– Operational errors– Security breaches, malicious alterations– Technology evolution – Object transformation (format obsolescence)– Infrequent access to most data

Using Hashes to Monitor Using Hashes to Monitor FilesFiles

• 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?

Audit Control Environment Audit Control Environment (ACE)(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 3rd party auditing.

• One number stored externally is used to audit tokens and hashes.

Hash AuthenticationHash Authentication

Hash 1 Hash 6Hash 5Hash 3 Hash 4Hash 2

Intermediate Hash ValuePrevious Round Hash

CSI (one hash value)

ChallengeHash

IHV

IHV

Gather Hashes During RoundCreate Merkel Tree For Supplied HashesLink to previous roundGenerate proof for hash

Token SampleToken Sample<token>

<token-class>SHA-256-0</token-class><digest-service>SHA-256</digest-service><name>/SRB3_2_1f.tar</name><round-id>1223</round-id><time-stamp>2008-07-22T11:03:45.059-0400</time-stamp><proof><element index="0"><hash>2e869e2ce41ede3ceb3af50f8aa2705067b3e67055b5b3d2787e2c294a95a869</hash></element><element index="0"><hash>6a925501991d7b4ff660d499416fd45a20dde161eb68e59fedc0f58208ad86cf</hash></element><element index="0"><hash>134432a6a6527162d24e99435e817511eeb89ddc03afbc6a30f23e404847cc06</hash></element><element index="1"><hash>1aeaf2d76976cf9759b0d63bc7acdf9c6df68875bfc9bcc0e22c19401aab0133</hash></element></proof>

</token>

How to scale?How to scale?• Two layers of Merkel tree

1. Short rounds(seconds), that generate Cryptographic Summary Information(CSI).

2. Each successive round includes previous CSI3. 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.

ComponentsComponents• 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

ACE – System ArchitectureACE – System Architecture

reply

Token Registry

hdd

Archiving Node

cd-romtape drive

request

ACE Audit Manager

Third-Party Integrity Management System

CryptoSummary

Information

reply

Token Registry

hdd

Archiving Node

cd-romtape drive

request

ACE Audit Manager

witnesses witnesses

Audit Policy Audit Policy

ACE AuditACE 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

Audit ManagerAudit 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!

ACE Audit ManagerACE Audit Manager• Dashboard for collection monitoring

LoggingLogging• All events logged

– Files offline, corrupt, re-available– Audit times, last seen

Error ReportingError Reporting• View all files that are not perfectly intact• Remove files from monitoring.• View events associated with files

Audit Manager FeaturesAudit Manager Features• Compare collections to hash list

– Same/different names, same/differing digests• Export collection details

– Hash export, wget crawl export• JSON interface for embedding statistics in

3rd party websites• Gateway to data

Fun with hashesFun with hashes• Ensure everything was uploaded

– Accepts a bag-it style manifest (hash + path)• Extract all the duplicates

– More exist than you think• Ensure collection replicas are complete• Locate renamed files

PerformancePerformance• Audit Manager (1.1beta3)• 1.25 million false digests (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 testChronopolis test• Three sites

– UMD, NCAR, SDSC• Three ACE AM installations• Independent monitoring at all sites• 30 day audit policy• Over 17Tb and 5.5 million files

Chronopolis TestChronopolis TestProvider Files Size(GB

)Time(h) Files/s MB/s

CDL 46,762 4,291 20:32 .63 59.44

SIO-GDC

197,718 815 6:49 8.05 34.00

ICPSR 4,830,625

6,957 122:48 10.93 16.11

NC-State

608,424 5,465 32:14 5.24 48.22

ACE SummaryACE Summary• High performance, Scalable• 3rd party auditable• Version 1.0 publically available

– Support for local files, SRB, iRODS

• http://adapt.umiacs.umd.edu/ace

• Standalone client available