flexcloud: reliable and secure cloud overlay · pdf file# 16 unreliable, proprietary and...

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

FlexCloud: Reliable and Secure Cloud Overlay Infrastructures

2013

Prof. Dr. Alexander Schill

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Who we are

Dr.-Ing. Josef Spillner Dipl.-Medieninf. Marc Mosch Dr.-Ing. Stephan Groß Dipl.-Medieninf. Yvonne Thoß Dr.-Ing. Anja Strunk (from left to right)

EU-funded research group

Exploring Cyber Physical Systems

Network Planning and Security

Internet Information Retrieval

Mobile & Ubiquitous Computing

Real-Time Collaboration

Energy Lab

Service & Cloud Computing

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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

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 applications SaaS/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-demand self service

Broadband network access

Resource pooling

Measured and optimized 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

Ado

pted

fro

m [

MeG

r201

1] a

nd [

BKN

T201

0]

Cloud Architecture Stack

Public

Hybrid

Private

Community

Con

veni

ence

User Control

Cloud Organization

Physical Resource Set (PRS)

Virtual Resource Set (VRS)

Programming Environment Execution Environment

Applications Services Applications

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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 cycle Hybrid cloud platform to integrate a user’s (cloud) resources, services and data. > Unified Cloud

Prevent Vendor-Lock-in + Integration of existing IT > Secure Cloud

Ensure data privacy and security > Managed Cloud

Keep the user in command > Efficient Cloud

Adapt to user preferences and cloud's vital signs

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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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π-Box distinguishes between public and sensitive data and enforces security mechanisms for the latter.

π-Cloud

π-Box

FlexCloud's Approach

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Analysis of structured, unstructured data and context information

PKI π-Cloud

?

Document classification concerning security requirements.

Addressee identification and derivation of respective keys.

Transparent Encryption

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Conceptual design of a user-centric cloud management solution •  Categorization of user groups concerning technical skills and organizational interests •  Guidelines for constructing adaptable graphical user interfaces •  Refinement of user profiles according to individual preferences

Organization of a user’s cloud resources •  Description of cloud resources and their (non-)functional properties •  System architecture for a reliable and scalable cloud resource directory •  Protocols for automatic (de-)registration of cloud resources within the π-Cloud

π-B

ox

π-Service Controller

π-Data Controller

π-Resource Manager

π-Cockpit

Peer-to-Peer Network

private resources (trustworthy)

public resources (not necessarily

trustworthy)

User Interface / GUI

User-controlled reliable data storage in the cloud •  Automatic assurance of availability, integrity and confidentiality •  Easy integration of existing IT environments •  Adaptable and optimizable storage with respect to user preferences

Service execution with respect to security and other non-functional requirements.

Data storage & distribution with

respect to security and other non-

functional requirements.

Infrastructure management

π-Box Architecture

User-controlled reliable service execution in the cloud •  Automatic composition and deployment of services with respect to security and other

non-functional properties •  Easy integration of existing IT environments

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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

Web access

Preprocessing Layer

Fragment level transformation (e.g. encryption)

File level transformation (e.g. compression)

Dispersal routine

Transport Layer Caching

Local persistence

Provider Storage API adapter

Reliable disk storage

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π-Data Controller

π-Cloud = Company Intranet

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Meta Data

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Secure Cloud Storage Integrator for Enterprises (System Architecture)

API FTP

CIFS

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π-Data Controller


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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

glibc glibc

libfuse

CIFS = Common Internet File System NFS = Network File System Ext3 = Third Extended File System SMB = Server Message Block FUSE = Filesystem in Userspace VFS = Virtual File System glibc = GNU C library

Implementation of the Shared Folder

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π-Data Controller


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Storing Files (2/5)

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Ensure availability despite of unreliable cloud storage providers …

n total # of shares a file is split into

k threshold, 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 𝑠∈𝑆 in 𝑛 shares 𝑠↓1 , …, 𝑠↓𝑛  with in 𝑛 shares 𝑠↓1 , …, 𝑠↓𝑛  with shares 𝑠↓1 , …, 𝑠↓𝑛  with 1.  Knowledge of any 𝑘 or more 𝑠↓𝑖  shares makes 𝑠 easily computable. or more 𝑠↓𝑖  shares makes 𝑠 easily computable. easily computable. 2.  Knowledge of any 𝑘−1 or fewer 𝑠↓𝑖  shares leave 𝑠 completely undetermined completely undetermined

(in the sense that all its possible values are equally likely).

Input: 𝑠

𝑠↓1  𝑠↓2  𝑠↓𝑛 

…

Dealer

Share holders store

Sharing

… Share holders

Reconstructor

Reconstruction

Output: 𝑠↑∗ 

s↓i↓1   𝑠↓𝑖↓2   s↓i↓k  

Secret Sharing aka Threshold Schemes

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[Sou

rce:

htt

p://

goo.

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atJC

]

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 a0:=s є S the secret to be shared where S is an

infinite field known to all share holders. Randomly choose (k-1) coefficients a1,a2,…ak-1 є S to build f(x):=Σai·xi. Calculate shares sj:=[j,f(j)] with j є ℕn.

Recovering: Use Lagrange interpolation to find coefficients of the polynomial including constant term a0.

s1

s2

Secret Sharing: More formalism

s3

Gra

phic

s ta

ken

from

Wik

iped

ia.

s

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.

•  Construction Be 𝑎↓𝑖 ≔𝑠∈𝑆 where 𝑖=1, …, 𝑘, i.e. 𝑓(𝑥)≔ ∑𝑖=1↑𝑘▒𝑠∙ 𝑥↑𝑖  . 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 𝑘 times as long as before. •  Length of each share is only 1/𝑘 -th of the length of the secret, and

if 𝑘 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 𝑘 arbitrary shares arbitrary shares

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

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π-Data Controller


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Meta Data

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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


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Storing Files (4/5)

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π-Data Controller


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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 Storage

Protocol Adapter: Storage protocol parameters and provider login data

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π-Data Controller


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Retrieving Files (1/3)

Dispersion parameters: n=6

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π-Data Controller


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Dispersion parameters: n=6, k=3

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π-Data Controller


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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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π-Box

SOHO Enterprise

π-Box Scalability

Embedded systems

AVM FRITZ!OS plugin

Home Server

Enterprise Server

Virtual Machine

SOHO: Small Office and Home Office

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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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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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… by connecting several π-Clouds and propagating data and services within one π-Cloud and to others. Simplified approach: assuming public, i.e. insecure π-Clouds Advanced approach: Trust relationships between π-Clouds

π-Box

π-Cloud

Building a cloud of clouds

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Towards a secure cloud life cycle

Cloud Adaption and Optimization Strategies for the compensation of SLA violations Strategies for minimization of energy consumption Mechanisms for the visuali- zation of complex Cloud Monitoring data

Fine-grained Service Level Agreements

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

Identification of assets and corresponding requirements

Deduction of monitoring targets from SLAs

Cloud Surveillance and Incident Detection Specification of monitoring targets and SLA violations Models for the proactive recognition of SLA violations and the evaluation of a Cloud‘s energy efficiency Mechanisms for reliable distributed Monitoring

Dynamic Provider Selection and Cloud Setup

Flexible distribution mechanisms for Cloud Platforms

Strategies for the performance optimization of Cloud Applications

Reputation consideration to improve reliability and trustworthiness

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Tomorrow's forecast:

still cloudy but sunny spots Contact: [email protected] [email protected] http://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.

flexcloud: reliable and secure cloud overlay · pdf file# 16 unreliable, proprietary and...

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