ePOST Serverless Email System

http://www.epostmail.org/POST: A Decentralized Platform for Reli

able Collaborative Applications

Seo, Dong Mahn16th June, 2005

2/37

Contents

Introduction Background Scoped Overlays POST Design ePOST Design Related Work Current Version Conclusions

3/37

Introduction

4/37

Introduction (1)

POSTThree basic services

Secure persistent single-copy storageMetadata based on single-writer logsEvent notification

Wide range of collaborative applicationsScalability, resilience and self-

organizationFrom users

CPU, disk space, network bandwidth

5/37

Introduction (2)

ePOSTCooperative, serverless email systemStorage, Network bandwidth from usersProvides

A severless, peer-to-peer email serviceSecure email among ePOST usersAn organically scaling service that requires no dedic

ated hardwareVery high availability and data durabilityCompatibility with POP/IMAP clients, SMTP mail ser

vers

6/37

Background (1)

Email SystemsSimple Mail Transfer Protocol (SMTP)Post Office Protocol (POP3) Internet Message Access Protocol (IMAP)Webmail

7/37

Background (2)

Peer-to-Peer OverlaysPastry

structured overlay networkself-organizing, highly scalable, and fault

tolerantunique identifier (160-bit id space)

8/37

Background (3)

Peer-to-Peer OverlaysPAST

distributed storage systemDistributed Hash Table (DHT)

Content Hash Blocks Certificate Blocks Public-Key Blocks

9/37

Background (4)

Peer-to-Peer OverlaysScribe

group communication system160 bit groupIdmulticast tree

10/37

Scoped Overlays (1)

DesignMulti-Ring Protocol above the Key-Based

Routing (KBR)

11/37

Scoped Overlays (2) Ring structure

12/37

Scoped Overlays (3)

Gateway nodesone in each ringuse the same nodeId in each ring

Routing target ringIdanycast

Global lookupringId

13/37

Scoped Overlays (4)

Multi-level ring hierarchies

14/37

POST Design (1)

User accounts identity certificate as a certificate block

secure hash of the users’ name as the handle

description of the usercontact address of the user’s current trusted

nodeany references to public metadata

associated with the accountpublic-key blocksigned with user’s private key

15/37

POST Design (2)

Single-copy storeconvergent encryption

allows a message to be disclosed to selected recipients

ciphertext (cryptographic & cipher)

16/37

POST Design (3)

Event notificationalert users and groups of users to

certain eventsavailability of a message. change in the

state of a user, change in the state of a shared object

Advanced Encryption Standard (AES) with a unique session key

17/37

POST Design (4)

Metadatasingle-writer logs Ivy

The log head and each log record are stored at a different set of nodes.

Garbage collectionremoving objects from the DHTLifetime

18/37

POST Design (6)

POST SecurityThreat modelData privacyData integrityData durabilityDenial of serviceFreeloading

19/37

ePOST Design (1)

20/37

ePOST Design (2)

Email storageEmail messages and MIME components in PO

ST’s single-copy store. Email delivery

using POST’s notification service Email folders

encrypted POST log

21/37

ePOST Design (3)

Incremental Deployment interoperate with server-based email

infrastructure Management

Software distributionStorageAccess

DiscussionFeasibility, Mailing Lists, Spam

22/37

Evaluation (1)

Timelinefrom Sept. 19, 2005 to Nov. 12, 2004average

26 nodesLinux and

Windows

23/37

Evaluation (2)

24/37

Evaluation (3)

25/37

Evaluation (4)

26/37

Evaluation (5)

27/37

Evaluation (6)

28/37

Evaluation (7)

29/37

Evaluation (8)

30/37

Evaluation (9)

31/37

Evaluation (10)

Single-Copy Storereduce the storage load by 6.1%30 users

300,000 email messages2.8 GBreduced to 3.2GB of unique datasavings of 15.5%254% increase in the effect of the single-

copy store.

32/37

Evaluation (11)

33/37

Evaluation (12)

34/37

Related Work

Collaborative Applications SENGMSG program, FTP, SMTP, POP3, IMAP Lotus Notes, MS Exchange Scalability

Porcupine System Hotmail, Google

Security spam, phishing scams PGP, GPG, DNS tricks

Peer-to-Peer Applications DHT OceanStore project, Kademlia, eDonkey2000 Coral-CDN, OpenDHT

35/37

Current Version

ePOST 2.4.2 27 May 2005

Rings Rice University Ring (rice.epostmail.org) Open Membership Ring (open.epostmail.org)

based on PlanetLab nodes

Future Features individual domain names multiple, simulations proxies multiple ePOST accounts

36/37

Conclusion

POSTdecentralized, serverless messaging systemhighly resilient and scalable messaging serviceenduring confidentiality, data integrity, and aut

henticationePOSTeasily provide

instant messaging, newsgroups, calendars, and shared whiteboards

37/37