Cryptography Seny Kamara Cryptography Group Microsoft Research - - PowerPoint PPT Presentation

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Cryptography Seny Kamara Cryptography Group Microsoft Research - - PowerPoint PPT Presentation

Nov 22, 2023 282 likes •640 views

Cloud Cryptography Seny Kamara Cryptography Group Microsoft Research Outline Cloud Architecture What is cloud computing? o Cloud Ecosystem Who provides and who consumes cloud services? o Cloud Cryptography What are the security

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Cloud Cryptography

Seny Kamara Cryptography Group Microsoft Research

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Outline

  • Cloud Architecture
  • What is cloud computing?
  • Cloud Ecosystem
  • Who provides and who consumes cloud services?
  • Cloud Cryptography
  • What are the security concerns & how can cryptography help?

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Computing as a Service

  • Computing is a vital resource
  • Enterprises, governments, scientists, consumers, …
  • Computing is manageable at small scales…
  • e.g., PCs, laptops, smart phones
  • …but becomes hard to manage at large scales
  • build and manage infrastructure, schedule backups, hardware

maintenance, software maintenance, security, trained workforce, …

  • Why not outsource it?

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Computing Architecture

Email, WWW, DBs,…

Applications

Windows, Linux, MacOSX,…

Platform

memory, disk, network,

Infrastructure

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Cloud Services

  • Infrastructure as a service
  • Service: customer can store data in the cloud
  • Customer: enterprise, developers
  • e.g., MS Azure storage, Amazon S3
  • Platform as a service
  • Service: customer can run its apps in the cloud
  • Customer: developers
  • e.g., MS Azure, Amazon EC2, Google AppEngine,
  • Software as a service
  • Service: customer makes use of app in the cloud
  • Customer: consumers & enterprise
  • e.g., web-based email, Flickr, delicious, Facebook, Office Web, Google

Docs, …

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Cloud Deployment Models

Public Private

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The Cloud Ecosystem

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Who Provides Cloud Services?

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Cloud Infrastructure Providers

  • Provide access to infrastructure
  • e.g., Amazon, Microsoft, Google, IBM, EMC, Equinix, AT&T, Verizon
  • Characteristics
  • Requires very large investments
  • build data centers
  • acquire expertise
  • provide physical security
  • energy consumption
  • …
  • Large (often) publicly traded companies
  • Have a reputation to uphold

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Cloud Service Companies

  • Provide cloud-based applications
  • e.g., Salesforce, GoGrid, NetSuite
  • Characteristics
  • Requires small investment
  • developers
  • Platform/infrastructure services from larger cloud providers
  • Startups (often) privately held

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Who Consumes Cloud Services?

  • Consumers
  • e.g., Facebook (500+ M), Web-based email (840 M), Flickr, Dropbox, …
  • Enterprise
  • E.g., Amazon EC2/S3, MS Azure, Google AppEngine, Google Apps
  • Governments
  • 120,000 US Dept. of Agriculture employees will move to MS cloud services
  • 17,000 Gen. Serv. Admin. Employees will move to Google cloud services
  • Local Governments
  • 100,000 NYC emplyees will move to MS cloud services
  • 34,000 L.A. emplyees will move to Google cloud services

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Cloud Cryptography

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Concerns

  • Outsider security
  • Can other tenants, hackers, competitors access my data?
  • Insider security
  • Can the cloud operator (and its employees) access my data?
  • Intellectual property
  • Can outsiders or insiders see my code and algorithms?
  • Compliance
  • Can I remain compliant if I move to the cloud?
  • Availability
  • Can I access my data or service at all times?

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Modern Cryptography

  • Primitives
  • e.g., encryption, digital signatures, hash functions, pseudo-random

generators, …

  • Protocols
  • e.g., key agreement, zero-knowledge proofs, multi-party computation
  • Security definitions
  • Formal definition of what it means to be secure
  • “Proofs” of security
  • Proof that primitive/protocol meets security definition
  • Unconditional security (e.g., one-time pad)
  • Conditional security (e.g., RSA, El Gamal,…)
  • Leads to very strong security guarantees
  • e.g., digital signatures are widely accepted in court
  • SHA-2, AES, ECC are certified for government use by NIST & NSA

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Modern Cryptography

EncK( )

Encryption No! Signatures $45B $5B

 

Secure Comp.

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Cloud Cryptography

  • Current crypto tools are inappropriate for the cloud
  • Due to assumptions about how tools will be used
  • Results in efficiency loss & insecurity
  • New tools
  • Homomorphic encryption
  • Searchable/Structured encryption
  • Proofs of storage
  • Server-aided secure computation

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Homomorphic Encryption

  • Encryption that supports comp. on encrypted data
  • Fully homomorphic [G09, DGHV10]
  • Partially homomorphic [SYY99, BGN05, IP07,GHV10a,GHV10b,KR11]
  • Guarantees that
  • Cloud never sees plaintext/message
  • Pros
  • FHE is general-purpose
  • Partial & parallel HE can be efficient
  • Cons
  • FHE is inefficient (but improvements are being made rapidly)

[…,G09,…]

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Homomorphic Encryption

K

EncK , F EncK F

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Searchable Encryption

  • Encryption that supports search on encrypted text
  • Symmetric key [SWP01,Goh03,CM05,CGKO06]
  • Public key [BDOP06, BKOS07,…]
  • Guarantees that
  • Cloud never sees documents
  • Cloud never sees search keywords
  • Pros
  • Symmetric variant is very efficient!
  • Cons
  • Reveals access and search patterns
  • [GO96] shows how to hide this but it is expensive

[SWP01]

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Searchable (Symm.) Encryption

tw

EncK EncK EncK

K

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Structured Encryption

  • Encryption that supports queries on encrypted data
  • Query over encrypted graphs [CK10]
  • Query over encrypted web graphs [CK10]
  • Guarantees that
  • Cloud never sees data
  • Cloud never sees queries
  • Pros
  • Symmetric variant is very efficient!
  • Cons
  • Reveals access and search patterns

[CK10]

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Structured Encryption

t

EncK EncK EncK

K

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Proofs of Storage

  • Tamper detection without knowing original file
  • Symmetric-key [JK07, SW08, DVW10]
  • Public-key [ABC+07, SW08, AKK10]
  • Guarantees that
  • Cloud will be caught if it tampers with data
  • Pros
  • Symmetric variant is efficient!
  • Verification does not require copy of original data
  • Cons
  • [JK07, ABC+07]

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Proofs of Storage ?

O(1) ≈ 200 bits

Petabytes

proof

K

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Server-Aided Secure Comp.

  • Joint computation w/o revealing inputs
  • (plain) secure computation [Yao82,GMW87,…]
  • Guarantees that
  • Parties will not learn each other’s inputs
  • Cloud will not learn parties’ inputs
  • Pros
  • General-purpose (e.g., data mining, voting, negotiations,…)
  • Efficient
  • Cons
  • [KMR11]

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Server-Aided Secure Comp.

y x f(x,y)

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Questions?

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References

  • [MG09]
  • The NIST Definition of Cloud Computing
  • http://csrc.nist.gov/groups/SNS/cloud-computing/cloud-def-v15.doc
  • [G09]
  • Craig Gentry
  • Fully Homomorphic Encryption from Ideal Lattices.
  • ACM Symposium on Theory of Computing, 2009.
  • [DGHV10]
  • Martin van Dijk, Craig Gentry, Shai Halevi and Vinod Vaikuntanathan
  • Fully Homomorphic Encryption Over the Integers
  • [SYY99]
  • Tomas Sanders, Adam Young and Moti Yung
  • Non-interactive Cryptocomputing for NC1
  • IEEE Symposium on the Foundations of Computer Science, 1999

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References

  • [BGN05]
  • Dan Boneh, Eu-Jin Goh and Kobi Nissim
  • Evaluating 2-DNF Formulas on Ciphertexts
  • Theory of Cryptography Conference, 2005
  • [IP07]
  • Yuval Ishai and Anat Paskin
  • Evaluating branching programs on encrypted data
  • Theory of Cryptography Conference, 2007
  • [GHV10a]
  • Craig Gentry, Shai Halevi and Vinod Vaikuntanathan
  • A Simple BGN-style Encryption Scheme from LWE
  • Advances in Cryptology – Eurocrypt, 2010

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References

  • [GHV10b]
  • Craig Gentry, Shai Halevi and Vinod Vaikuntanathan
  • i-hop Homomorphic Encryption Schemes
  • Advances in Cryptology – CRYPYO, 2010
  • [KR11]
  • Seny Kamara and Mariana Raykova
  • Parallel Homomorphic Encryption
  • Under submission
  • [SWP01]
  • Dawn Song, David Wagner and Adrian Perrig
  • Practical Techniques for Searches on Encrypted Data
  • IEEE Security and Privacy Symposium, 2000

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References

  • [Goh03]
  • Eu-Jin Goh
  • Secure Indexes
  • http://eprint.iacr.org/2003/216
  • [CM05]
  • Yang-Chen Chang and Michael Mitzenmacher
  • Privacy preserving keyword searches on remote encrypted data
  • Conference on Applied Cryptography and Network Security, 2005
  • [CGKO06]
  • Reza Curtmola, Juan Garay, Seny Kamara and Rafail Ostrovsky
  • Symmetric Searchable Encryption: Improved Definitions and Efficient

Constructions.

  • ACM Conference on Computer & Communication Security, 2006

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References

  • [BDOP04]
  • Dan Boneh, Giovanni di Crescenzo, Rafail Ostrovsky and Giuseppe

Persiano

  • Public-Key Encryption with Keyword Search
  • Advances in Cryptology – Eurocrypt, 2004
  • [BKOS07]
  • Dan Boneh, Eyal Kushilevitz, Rafail Ostrovsky, William E. Skeith III
  • Public Key Encryption That Allows PIR Queries
  • Advances in Cryptology – CRYPTO, 2007
  • [CK10]
  • Melissa Chase and Seny Kamara
  • Structured Encryption and Controlled Disclosure
  • Advances in Cryptology – Asiacrypt, 2010

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References

  • [JK07]
  • Ari Juels and Burt Kaliski
  • PORs: Proofs of Retrievability for Large Files
  • ACM Conference on Computer & Communications Security, 2007
  • [ABC+07]
  • Giuseppe Ateniese, Randal C. Burns, Reza Curtmola, Joseph Herring, Lea

Kissner, Zachary N. J. Peterson, Dawn Xiaodong Song

  • Provable Data Possession at Untrusted Stores
  • ACM Conference on Computer & Communications Security, 2007
  • [SW08]
  • Hovav Shacham, Brent Waters
  • Compact Proofs of Retrievability
  • Advances in Cryptology – Asiacrypt, 2008

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References

  • [DVW09]
  • Yevgeniy Dodis, Salil P. Vadhan, Daniel Wichs
  • Proofs of Retrievability via Hardness Amplification
  • Theory of Cryptography Conference, 2009
  • [AKK10]
  • Giuseppe Ateniese, Seny Kamara and Jonathan Katz
  • Proofs of Storage from Homomorphic Identification Schemes
  • Advances in Cryptology – Asiacrypt, 2010
  • [KMR11]
  • Seny Kamara, Payman Mohassel and Mariana Raykova
  • Server-Aided Secure Computation
  • Under submission

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