Outsourcing Database Services

Đỗ Phước Hoàng Tường Lân 50701257Nguyễn Minh Thông 50702368Lê Tuấn Đạt 50700487

Outline

• Service providers models for ODBS

• Two extreme security protocols

• Balancing Security and Efficiency

Introductions

Advances in networking Tech. & growth of the Internet -> New trend towards outsourcing data management (musics, videos, pictures…).

Without exception, Outsourcing Database Services has been being developed incessantly.

Introductions (cont.)

Commercial companies and especially Research community use the Outsourcing Database Services (ODBS) models to store, maintain and retrieve their data. WHY ?

DBMSs

Data owners

Clients

Store & Retrieve

RetrievePay for the services

Introductions (cont.)

Reduce cost in purchasing softwares and hardwares infrastructure.

Needn’t pay for deployment, maintenance and upgrade the system

….

The Reasons :

* But every coins has two sides *

Introductions (cont.)The Problems :Security !!!

Client stores its private data at an external service provider who is typically not fully trusted.

How is clients’ private data protected against sophisticated attackers?

How clients can operate on their outsourced data without worrying about leak of their sensitive information ?

Introductions (cont.)

Security requirements :

Data confidentiality User privacy Data privacy Authentication and data integrity

Data confidentiality : Outsiders and even the server’s operators (database administrators) are not able to see the client’s outsourced data contents in any case

User privacy : Clients do not want the server to know about their queries and the returned results

Data privacy : Clients are not allowed to get more information than what they are querying on the server.

Authentication and data integrity : Clients must be ensured that data returned from the untrusted server has originated from the data owner and has not been tampered with

Example :An organization M has a DNA database containing patterns about various diseases. M stores these DNA patterns on a database server DB and allows a client A to access the database to get information with respect to A’s DNA sequence

Organization M

DNA database(Untrusted server)

Outsourcing(Data confidentiality problem)

Client AQueries

(User privacy problem)

(Data privacy problem)

Responses

The need of data confidentiality, data or user privacy depends on particular scenarios in the ODBS model and this must be considered carefully.

Example : DB is hired just for M to use, i.e. client A is M itself and M is outsourcing its database services only to make use of the advantages of the ODBS model, then, although the data privacy is unnecessary in this case, neglecting the user privacy as mentioned above may potentially lead to expose the outsourced data to danger, even if they have been encrypted

Service providers models for ODBS

Service providers models for ODBS

Four mains service provider (SP) model : UP-DP model (User Privacy – Data Privacy) UP-nDP model (User Privacy – not Data

Privacy) DC-UP model (Data Confidentiality – User

Privacy) DC-UP-DP model (Data Confidentiality – User

Privacy – Data Privacy)

UP-DP model : Data owners are also the SPs. They sell information and charge clients for using their services. The sold information is important and thus the SP is concerned about the data privacy. In this model, the client is concerned about the user privacy.

UP-nDP model : Similarly to the UP-DP model, data owners here are also the SPs and they charge clients only for using their services, but the stored data is public. In this model, the client is also concerned about the user privacy, but the SP is not concerned about the data privacy.

DC-UP model: Data owners are also unique clients and their data is outsourced to the external database server. In this model the data owner (also the client) is only concerned about the data confidentiality and the user privacy

UP-nDP model : Data owners outsource their data and charge clients for using their data information. The data owner is concerned about both the data confidentiality and data privacy .The client, in turn, is concerned about the user privacy. Moreover, the data owner also takes the client role when accessing its outsourced data on the server and, in this case, the data owner is concerned about the user privacy as well.

* Each SP model requires different security objectives and thus different security techniques/ protocols have been invented to satisfy these objectives

For User privacy :

Private information retrieval (PIR) protocol First introduce by Chor and colleagues. Allow a client to access a database without

revealing to the server both the query and the returned result

Database

Data server

Clients

Query (i-th record)

Response (N-record[i])

i-th is hidden from the server

*Not supporting Writing operations*Hight IO-cost

Private information storage (PIS) protocol Support the writing operations privately

Repudiative information retrieval(PIS) protocol

Preserve the user privacy but with a better IO-cost

Reduce IO-cost from O(NlogN) -> O(sqrt(N))User anonymity

Extreme protocol

For Data privacy :Symmetrically private information retrieval (SPIR) protocol

Built on the basis of any PIR protocol with the aim to satisfy both user and data privacy requirements

Extreme protocol

For Data confidentiality :

Index of range, Hashbased methods

Extreme protocol

Proposed by Hacigümüs and team. Relies on partitioning of the domains of client

tables’ attributes into sets of intervals, is suitable for both exact match and range queries

For Authentication and data integrity :Merkle hash tree’s

Use a binary search trees to construct authenticated dictionary structures.

Data Index problems: Nowaday, data are build structurally for the

convenience of insertion, retrieval and removal of records

Tree-based structures are used, B-tree,B+tree…

An Example of B+-tree on Attribute CustomerName.

John

Bob Ha Rose Trang

TrangRose Sam

John Linh

Alice Anne

Bob Carol

Ha

0

1 2

4 5 6 7 8

Base on the sequence of nodes be accessed, the user will get more information showing => Data privacy problem.

Using the this sequence of nodes, by some data mining techniques, server can infer some sensitive information => Data confidentiality problem.

*To solve those security problems, Lin and Candan introduced new techniques to access outsourced tree nodes, called access redundancy and node swapping.

Without employing special security hardware equipment, we can’t prevent attacks made by exploiting outsourced tree-based index structures. How can we deal with this ?

Two Extreme Security Protocols

Two Extreme Security Protocols

In order to protect the outsourced data from possible intruders we encrypt the data prior to outsourcing

NID Node

012345678

(1,John,2,-,-1) (3,Bob,4,Ha,5) (6,Rose,7,Trang,8)(Alice,Anne,4) (Bob,Carol,5) (Ha,-,6) (John,Linh,7) (Rose,Sam,8) (Trang,-,-1)

NID Encryped Node

012345678

D0a1n2g3Kh75nhs& T9&8ra§ÖÄajh³q91 H&$uye”µnÜis57ß@ L?{inh*ß²³&§gnaD Wh09a/[%?Ö*#Aj2k j8Hß}[aHo$§angµG #Xyi29?ß~R@€>Kh ~B³!jKDÖbd0K3}%§ T-§µran&gU19=75m

B+ Table

B+ Encrypted Table

Two Extreme Security Protocols (cont.)

DC-UP model’s formula

DC+UP = Encryption + PIR Protocol

For private reading and writing operationsDC+UP = Encryption + PIS

Protocol

Two Extreme Security Protocols (cont.)DC-UP-DP model

A trusted third-party will be concerned like a secure coprocessors

DB

MA

K root

i-node i-node i-node

leaf leaf leaf leaf leaf

A Security Protocol for the DC-UP-DP Model

Balancing Security and Efficiency

Balancing Security and Efficiency

What is Efficiency ?

• CPU cost• IO cost• Memory cost

DC-UP (and DC-UP-DP as well) model -> PIR Protocol’s efficiency

* The questions is : How will the client’s queries be performed effectively, efficiently and obliviously over encrypted data without revealing any information about both data and queries to unauthorized people?

Balancing Security and Efficiency (cont.)

Modifications for the DC-UP Model

* RIR is used instead of PIR for the goal of reducing cost

DC + UP = Encryption + RIR protocol

* Similarly to PIS, the replacement is RIS

DC + UP = Encryption + RIS protocol

Balancing Security and Efficiency (cont.)

Modifications for the DC-UP Model (cont.)

* In order to support the oblivious search on a single outsourced search tree, new two techniques called Access redundancy and Node swapping was developed. PIR/RIR-like protocols with these techniques can be used for DC-UP model

Access redundancy• This technique requires that whenever a

client accesses a node, called target node, she asks for a set of m-1 randomly selected nodes in addition to the target node from the server.

• Better performance but worse security level. So what is the weakness ?

Node swapping

• Overcome the former technique’s weakness.

• There’s still limitations and weakness.

Balancing Security and Efficiency (cont.)

Modifications Related to the DC-UP-DP Model• All possible modifications for the DC-UP

model can also be suitably applied to the DC-UP-DP model

• DB now stores only leaf nodes of the tree.• It is not necessary to encrypt the meta-data

stored at K

ConclusionsODBS model Outsourcing data Depending on external service providers (untrusted) Dealing with securities issues A trade-off between Security and Efficiency.

Sources• Paper of Mr. Dang Tran Khanh• Wikipeadia