CS6262 Lecture 19 - Property Preserving Encryption

What makes shared resources in cloud computing both beneficial and risky?

Shared resources increase efficiency but also create security vulnerabilities

In a cloud environment, what is a common target for attackers?

Data stored or processed in the cloud

Why is data considered a valuable target in cloud environments?

Attackers aim to steal sensitive information stored or processed in the cloud

What is the main challenge when encrypting data for cloud applications?

Encryption protects data from adversaries but prevents applications from using it directly

How does property-preserving encryption differ from standard encryption?

It preserves selective properties of plaintext such as equality or order

What is the purpose of searchable encryption?

To enable searching of encrypted data using encrypted keywords

What does secure computation enable in a multi-party setting?

Multiple parties can compute a function with inputs that remain private

How does homomorphic encryption work?

Computations performed on ciphertext produce results equivalent to computations on plaintext

What is functional encryption designed to do?

Provides the ability to learn a function of encrypted data without learning the data itself

What is the main advantage of Property Preserving Encryption in cloud environments?

Applications can work on encrypted data without modification

What is a potential concern with Property Preserving Encryption?

Preserving properties may leak sensitive information

In equality-preserving encryption, what property is maintained?

Equality between values

What type of information is leaked in equality-preserving encryption?

Frequency of repeated values

In order-preserving encryption, what property of the plaintext is preserved?

Relative ordering

What types of information are leaked in order-preserving encryption?

Order and frequency distributions

What is the goal of an inference attack in a cloud environment?

Recover plaintext from ciphertext using auxiliary information

What type of public information can help inference attacks?

Auxiliary data such as statistical distributions

What type of attack can defeat equality-preserving encryption?

Frequency analysis attack

How does an attacker begin a frequency analysis attack?

Sort encrypted values and record their frequencies

How does an attacker match ciphertext to plaintext during a frequency attack?

By comparing encrypted frequency histograms to known plaintext distributions

What is the goal in a generalized frequency analysis attack?

To find the best mapping between ciphertext and plaintext minimizing histogram mismatch

What does the cost function represent in a generalized frequency attack?

The mismatch between ciphertext and plaintext histograms

What type of attack is more effective than sorting for order-preserving encryption?

Cumulative attack

What can an adversary learn from a column encrypted with order-preserving encryption?

Frequencies and relative ordering of values

What is the empirical cumulative distribution function (CDF) used for in cumulative attacks?

Matching ciphertext to plaintext using ordering information

How does a cumulative attack improve plaintext matching?

Uses both frequency and CDF information to minimize mismatch

Which mathematical problem category does cumulative attack mapping fall into?

Linear Sum Assignment Problem

What is the main privacy risk when encrypting data on a cloud server but keeping keys locally?

Data access patterns may reveal sensitive information

Why is fetching encrypted data locally for computation inefficient?

Access patterns still leak usage information

What is the main goal of Oblivious RAM (ORAM) in cloud computing?

To hide access patterns from the cloud provider

How does ORAM make access patterns independent of real operations?

Uses fixed-size blocks, dummy operations, and re-encryption/shuffling

What type of encryption does ORAM use?

Standard encryption

Why are dummy accesses used in ORAM?

To make read and write operations indistinguishable

How does ORAM handle data objects to prevent distinguishing them?

All objects are fixed size and appear identical

What is the current status of ORAM research?

It is an active and ongoing research area

Why does an ORAM client need a private source of randomness?

To generate unpredictable access sequences

Is data encryption still required when using ORAM?

Yes, encryption protects data content from the cloud provider

What is the purpose of performing both a read and a write for each ORAM access?

To hide whether the operation is actually a read or write