Department of Computer Science | Institute of Systems Architecture | Chair of Computer Networks

FlexCloud: Reliable and Secure Cloud Overlay Infrastructures

2013

Prof. Dr. Alexander Schill

# 3

Cloud Computing …

• What is it all about?

• Problems

• π-Box: Building your personal secure cloud

• π-Data Controller: Secure Cloud Storage

• Conclusion & Future Work

Outline

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The shape of a cloud …

… is in the eye of the beholder.

IaaS/PaaS*

Cloud Operating System, part of Azure Platform

* SaaS = Software as a Service PaaS = Platform as a Service IaaS = Infrastructure as a Service

PaaS*

Development and hosting of web applicationsSaaS/PaaS*

Business cloud services focussing on customer

relationship management

IaaS*

Migration of virtual machines between private

and public clouds

SaaS*

Customized applications for business and home user, based on Google

App Engine, e.g. collaboration tools

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Cloud Computing Characteristics

Cloud Computing is …

… the on-demand and pay-per-use application of

virtualised IT services over the Internet.

On-demandself service

Broadband networkaccess

Resource pooling

Measured andoptimized service

Rapid elasticity

Adopted from the NIST Definition of Cloud Computing [MeGr2011]

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Service & Deployment Models

Software Services (SaaS)

Platform Services (PaaS)

Infrastructure Services (IaaS)

User Interface Machine Interface

Components Services

Compute Network Storage

User/Clients

Ad

op

ted

fro

m [

MeG

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11

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[B

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Cloud Architecture Stack

Public

Hybrid

Private

CommunityC

onvenie

nce

User Control

Cloud Organization

Physical Resource Set (PRS)

Virtual Resource Set (VRS)

Programming Environment

Execution Environment

Applications Services

Applications

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Cloud Computing …

• What is it all about?

• Problems

• π-Box: Building your personal secure cloud

• π-Data Controller: Secure Cloud Storage

• Conclusion & Future Work

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Reliability and security when giving up physical possession> Failure of monocultures> Cloud providers‘ trustworthiness> Staying in control

Problems of Cloud Computing

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FlexCloud Objectives

π-Cloud: Establishing a secure cloud computing life cycleHybrid cloud platform to integrate a user’s (cloud) resources, services and data.

> Unified CloudPrevent Vendor-Lock-in + Integration of existing IT

> Secure CloudEnsure data privacy and security

> Managed CloudKeep the user in command

> Efficient CloudAdapt to user preferences and cloud's vital signs

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Cloud Computing …

• What is it all about?

• Problems

• π-Box: Building your personal secure cloud

• π-Data Controller: Secure Cloud Storage

• Conclusion & Future Work

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Subsume all end devices within a Personal Secure Cloud (π-Cloud) controlled by the π-Box.

π-Cloud

π-Box

FlexCloud's Approach

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Analysis of structured, unstructured data andcontext information

PKIπ-Cloud

?

Document classification concerning security requirements.

Addressee identification and derivation of respective keys.

Transparent Encryption

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Cloud Computing …

• What is it all about?

• Problems?

• π-Box: Building your personal secure cloud

• π-Data Controller: Secure Cloud Storage

• Conclusion & Future Work

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Unreliable, proprietary

and insecure

cloud storage

Unreliable, low quality hard disk

Increasing Availability: from RAID to RAIC

RAID:Redundant Array of Independent Disks

RAIC:Redundant Array of Independent Clouds

Integration Layer

Logical partition

Preprocessing Layer

RAID level redundancy routine (mirror, stripe, …)

Transport Layer

Block resources

Reliable, universal

and secure cloud

storage

Integration Layer

Versioning

Distributed file system

Webaccess

Preprocessing Layer

Fragment level transformation (e.g. encryption)

File level transformation(e.g. compression)

Dispersal routine

Transport LayerCaching

Local persistence

Provider Storage API adapter

Reliable disk storage

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π-Data Controller

π-Cloud =Company Intranet

Clo

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Secure Cloud Storage Integrator for Enterprises (System Architecture)

WebDAV

HTTP

APIFTP

WebDAVHTTP

CIFS

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π-Data Controller

π-Cloud =Company Intranet

Clo

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Storing Files (1/5)

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• Technology: FUSE (Filesystem in Userspace)

• CIFS/SMB network share on proxy file server

• Unified user interface for arbitrary cloud storage services

• Utilizing CIFS access control mechanisms

User space

Kernel

VFS

FUSE

NFS

Ext3

…

ls - /tmp/fuse

./xmp /tmp/fuse

glibcglibc

libfuse

CIFS = Common Internet File System NFS = Network File SystemExt3 = Third Extended File System SMB = Server Message BlockFUSE = Filesystem in Userspace VFS = Virtual File Systemglibc = GNU C library

Implementation of the Shared Folder

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π-Data Controller

π-Cloud =Company Intranet

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Storing Files (2/5)

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Ensure availability despite ofunreliable cloud storage providers …

ntotal # of shares a file is split into

kthreshold, i.e. # of necessary shares to reconstruct

E.g. k=6, n=8 If k < n, we need redundant information.

File Dispersion

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Objective: Divide a secret in shares with

1. Knowledge of any or more shares makes easily computable.

2. Knowledge of any or fewer shares leave completely undetermined (in the sense that all its possible values are equally likely).

Input:

𝑠1 𝑠2 𝑠𝑛…

Dealer

Share holders store

Sharing

… Share holders

Reconstructor

Reconstruction

Output:

si1𝑠𝑖2 sik

Secret Sharing aka Threshold Schemes

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Secret Sharing:An informal example with 2 shares

Visual Cryptography [NaSh1994]

Simplification: n = k = 2

Secret cannot be determined independently!

… revealed!

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Shamir's scheme [Shamir1979]

Idea: It takes k points to define a polynomial of degree k-1.Sharing: Be a

0:=s є S the secret to be shared where S is

an infinite field known to all share holders.Randomly choose (k-1) coefficients a

1,a2,…a

k-1 є S to build

f(x):=Σai·xi.

Calculate shares sj:=[j,f(j)] with j є ℕ

n.

Recovering: Use Lagrange interpolation to find coefficients of the polynomial including constant term a

0.

s1

s2

Secret Sharing: More formalism

s3

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Blakley's scheme [Blakley1979]

Idea: Any n nonparallel n-dimensional hyper-planes intersect at a specific point.

Sharing: Encode the secret as any single coordinate of the point of intersection.

Recovering: 1. Calculating the planes' point of intersection.2. Take a specified coordinate of that

intersection.

Example:n≥3, k=3

1 share available 2 shares available 3 shares available

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Information Dispersal:Computationally secure secret sharing

Rabin's scheme [Rabin1989]

• Guarantees only availability but no secrecy.

• ConstructionBe where , i.e. .Rest as with Shamir's secret sharing.

• Properties• With a polynomial and shares of the same size as before, we can now

share a value times as long as before.• Length of each share is only -th of the length of the secret, and

if shares must be sufficient for reconstruction, one can obviously not get shorter.➔ Space optimal

• However, one might gain some information if he gets access to several shares.➔ Computationally secure

More efficient information dispersal schemes• Need to be maximum distance separable to use arbitrary shares

for reconstruction.• Examples: Cauchy-Reed-Solomon, Liberation, Blaum-Roth [PSS2008]

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π-Data Controller

π-Cloud =Company Intranet

Clo

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Storing Files (3/5)

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+ SHA256

+ SHA256

+ SHA256

+ SHA256

AES-CBC

AES-CBC

AES-CBC

AES-CBC

Cryptography: Confidentiality & Integrity

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π-Data Controller

π-Cloud =Company Intranet

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Storing Files (4/5)

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π-Data Controller

π-Cloud =Company Intranet

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Storing Files (5/5)

Stored Meta Data per component• Shared Folder: General file system information, e.g. file size, access

rights …

• File Dispersion: Used dispersion algorithm/parameters (n, k), shares‘ locations

• Cryptography: Used cryptographic keys and calculated checksums per share

• Cloud StorageProtocol Adapter: Storage protocol parameters and provider login data

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π-Data Controller

π-Cloud =Company Intranet

Clo

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Pro

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Retrieving Files (1/3)

Dispersion parameters: n=6

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π-Data Controller

π-Cloud =Company Intranet

Clo

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Pro

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Retrieving Files (2/3)

Dispersion parameters: n=6, k=3

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π-Data Controller

π-Cloud =Company Intranet

Clo

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Pro

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Retrieving Files (3/3)

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[SGS11] web interface for π-Cockpit

[SBM+11]π-Cockpit desktop application

ResUbic Cloud Storage Allocator for Cyber Physical Systems

Prototype Implementation

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Performance Evaluation Upload

Towards User Centric Data Governance and Control in the Cloud

Test case π-Box used # local storage # cloud storage # encrypted shares

1 No 0 1 0

2 Yes 0 1 0

3 Yes 8 0 0

4 Yes 4 4 4

5 Yes 0 8 8

File size: 24 MB; Dispersion parameters: n=8, k=6;Cryptography parameters: AES (256 bit, 14 iterations), SHA256;Network Up/Downlink: 10/20 Mbit/s

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Performance Evaluation Download

Towards User Centric Data Governance and Control in the Cloud

Test case π-Box used # local storage # cloud storage # encrypted shares

1 No 0 1 0

2 Yes 0 1 0

3 Yes 8 0 0

4 Yes 4 4 4

5 Yes 0 8 8

File size: 24 MB; Dispersion parameters: n=8, k=6;Cryptography parameters: AES (256 bit, 14 iterations), SHA256;Network Up/Downlink: 10/20 Mbit/s

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Cloud Computing …

• What is it all about?

• Problems?

• π-Box: Building your personal secure cloud

• π-Data Controller: Secure Cloud Storage

• Conclusion & Future Work

# 38

Results so far & future work (π-Data Controller)

• Integration of existing cloud storage services (Cloud-of-Clouds)• Proxy server for transparent mediation

➔ easy to use for end-user, common scheme for enterprises• Good performance, high security & data control for the user

• Data store for database system (block-based dispersion)• Collaboration scenarios, file sharing, access by external

entities• Securing the meta data database• Automatic classification of data• Improving performance, e.g. scheduling algorithms,

caching/prefetching, parallelization• Optimized cloud storage

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Towards a secure cloud life cycle

Cloud Adaption and Optimization

Strategies for the compensation ofSLA violationsStrategies for minimization ofenergy consumptionMechanisms for the visuali-zation of complex CloudMonitoring data

Fine-grained Service Level Agreements

Methods to determine fine-grained non-functional properties of Cloud Services

Identification of assets andcorresponding requirements

Deduction of monitoringtargets from SLAs

Cloud Surveillanceand Incident Detection

Specification of monitoringtargets and SLA violationsModels for the proactive recognition ofSLA violations and the evaluation of aCloud‘s energy efficiencyMechanisms for reliable distributed Monitoring

Dynamic ProviderSelection and Cloud Setup

Flexible distribution mechanisms forCloud Platforms

Strategies for the performance optimization ofCloud Applications

Reputation consideration to improve reliabilityand trustworthiness

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Tomorrow's forecast: still cloudy but sunny spots

Contact: alexander.schill@tu-dresden.destephan.gross@tu-dresden.dehttp://flexcloud.eu/

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References

[BKNT2010] C. Baun, M. Kunze, J. Nimis and S. Tai: Cloud Computing. Web-basierte dynamische IT-Services. Springer Verlag, 2010.

[Blakley1979] G. R. Blakley: Safeguarding cryptographic keys; AFIPS Conference Proceedings Vol. 48, National Computer Conference (NCC) 1979, 313-317.

[MeGr2011] P. Mell and T. Grace: The NIST Definition of Cloud Computing. NIST Special Publication 800-145, September 2011.

[NaSh1994] M. Naor and A. Shamir, Visual Cryptography , Eurocrypt 94.

[PSS2008] J. S. Plank, S. Simmerman, C. D. Schuman: Jerasure: A Library in C/C++ Facilitating Erasure Coding for Storage Applications – Version 1.2. Technical Report CS-08-627, University of Tennessee, 2008.

[Rabin1989] M. O. Rabin: Efficient Dispersal of Information for Security, Load Balancing, and Fault Tolerance; Journal of the ACM 36/2 (1989) 335-348.

[SBM+2011] J. Spillner, G. Bombach, S. Matthischke, R. Tzschicholz, and A. Schill: Information Dispersion over Redundant Arrays of Optimal Cloud Storage for Desktop Users. In: IEEE International Conference on Utility and Cloud Computing. Melbourne, Australien, December 2011.

[SGS2011] R. Seiger, S. Groß, and A. Schill: A Secure Cloud Storage Integrator for Enterprises. In: International Workshop on Clouds for Enterprises. Luxemburg, September 2011.

[Shamir1979] A. Shamir: How to Share a Secret; Communications of the ACM 22/11 (1979) 612- 613.