Security without identification -

By,

Ajinkya Kulkarni

A presentation on

Department of Computer Science

University of Alabama in Huntsville

Author : David Chaum, Communications of the ACM, vol. 28, 1985.

(20 Jan 2009)

Transaction systems to make big brother obsolete

About the author

David Chaum is the inventor of many cryptographic protocols, including blind signature schemes, commitment schemes, and digital cash.

In this In this presentationpresentation

1) Problems addressed by Authors

2)Typical Solution and its Problem

3) New Approach proposed by Author

4) The Feasibility of New Approach

4.1) Communication Transaction

Problems Solution

4.2) Payment Transaction

Problems Solution

4.3) Credential Transaction

Problems Solution

Unconditional UntraceableCommunication

Digital Signature

Blind Signatures for Untraceable Payment

Individuals can not control the way in which information about themselves is used Sometimes information may be obsolete , inaccurate or otherwise inappropriate.

1 Problems (1/3)1 Problems (1/3)

Bank

Mobile Operator

Shops

Websites

BlogsEmployer

Fitness Center

University

Bob

1 Problems (2/3)1 Problems (2/3)Computers could be used to infer individuals’ life styles and habits

Fitness Center6 PM Wall Mart

Every Friday

PC Lab8 AM On Campus Job

9 AM

Big Brother is Watching You

Classes2 PM

Bank

Job

FC

WM

8 AM

9 AM

Gas

6 PM

Friday

1

2

3

4

5

Schedule

2 PM

Bob

Bad Guys

1 Problems (3/3)1 Problems (3/3)

Uncertainty about security of personal information

May cause people to alter their observable activities

Organization are vulnerable to abuses by individuals.

Bank

Job

FC

WM

8 AM

9 AM

Gas

6 PM

Friday

1

2

3

4

5

Schedule

2 PM

Bad Employee

Bad GuysInternet

2 Typical Solution and it’s 2 Typical Solution and it’s ProblemProblem

Perhaps in combination with national identity cards or even finger prints .

To devise more pervasive, efficient, and interlinked computerized record-keeping system,

But, this would exacerbate the problem of individuals’ loss of monitorability and the control

Would likely be unacceptable to many

3 New Approach (Proposed by 3 New Approach (Proposed by Author)Author)

3Differences

3 New Approach Details3 New Approach Details

Current systems emphasize the one-sided security of Organizations attempting to protect themselves from individuals

Personal card computers Wall Mart

The new approach allows all parties to protect their own interests

Wall Mart BillItems Purchased

1 Box

Total Bill Amount : $10

Pay

Bob

4 The Feasibility of New Approach 4 The Feasibility of New Approach

The feasibility of new approach can be demonstrated for a comprehensive set of three kinds of consumer transaction

Communication Transaction

4.1

Payment Transaction

4.2

Credential Transaction

4.3

4.1 Communication Transaction4.1 Communication Transaction

As more communication travels in electromagnetic and digital form

Possibility of exposure of tracing information.

It becomes easier to learn more about individual from their communication

Morning

Afternoon

Evening

Bob

System Administrator

SSN

Call HistoryAddress

4.1.1 Problems in Communication 4.1.1 Problems in Communication TransactionTransaction

Current systems provide inadequate protection

Hand written signature are easily forged

▶ By installing tamper resistant identity card

But these approach rely on tracing information

▶ By keeping records of message delivered, to provide certificate delivery

Solution under Current Approach

And thus are in fundamental conflict with individuals' ability to control access to information about themselves

4.1.2 Solution for Communication 4.1.2 Solution for Communication Transaction (Using New Approach)Transaction (Using New Approach)

Messages are untraceable

4.1.2.1 Unconditional Untraceable

4.1.2.2 Digital Signature

Except for the recipient's ability to authenticate them as having been sent by the owner of a particular pseudonym

4.1.2.1 Unconditional Untraceable 4.1.2.1 Unconditional Untraceable

Welcome

One of the three of you has already

paid for coffee

Who paid?If Bob has

paid, we must know,

because we invited him for coffee

But if one of us paid, Bob should not

know about it

B

A

4.1.2.1 Unconditional Untraceable 4.1.2.1 Unconditional Untraceable

Bob

We will say aloud which side the coin

falls onB

A

Let’s flip a coin

behind menu card

Agree

If one of us paid , then we should

say the opposite side

Menu Card

4.1.2.1 Unconditional Untraceable 4.1.2.1 Unconditional Untraceable

Bob

B

A

Head

Case 1: B has paid Tail

I know, one of them has

paid, but can not

determine who?Menu Card

4.1.2.1 Unconditional Untraceable 4.1.2.1 Unconditional Untraceable

Bob

B

A

Head

Case 2: Bob has paid Head

Menu Card

4.1.2.2 Digital Signature4.1.2.2 Digital Signature

I

Won

1 Billion Dollar

我

Digital Codebook

韩元

1 亿美元

1 亿美元

韩元

我

1 Billion Dollar

Won

I

我 韩元 1 亿美元

Bob Alice

I Won 1 Billion Dollar

English Chinese

Private Key

Public Key

4.2 Payment Transaction 4.2 Payment Transaction

Automation is giving the providers of these systems easy access to revealing and extensive information about individuals

Today many paper transaction records of when, how much, and to whom payment was made are translated into electronic form

Payment systems are being automated

E.g. Shopping, Travelling, Bank , Education

Computerization is extending data capture potential of payment systems

4.2.1 Problems in Payment 4.2.1 Problems in Payment TransactionTransaction

Uncollectable Payments by consumer

Check drawn against insufficient funds

Credit card misuse

Theft of paper currency

Envelope

4.2.2 Solution for Payment Transaction 4.2.2 Solution for Payment Transaction (Using New Approach)(Using New Approach)

Blind Signatures for Untraceable Payment

----------------------------Slip

Carbon Paper

Bank Signature worth $ X

Bank deducts $ X from Bob Account

Bank can not see the slip through the envelope

Bob

Bank

4.2.2 Solution for Payment Transaction 4.2.2 Solution for Payment Transaction (Using New Approach)(Using New Approach)

Blind Signatures for Untraceable Payment

----------------------------Slip

Envelope

Verifies proper signature markBob

Shop

Bank also verifies signature mark

Since it uses same signature for all account holder, it can not learn which account the funds were withdrawn from

Thus, Payment are untraceable

Bank

4.3 Credential Transactions4.3 Credential Transactions

Individuals must show credentials in relationships with many organizations.

Problem arise when unnecessary data are revealed in the process

Some credentials, such as passports , drivers’ licenses, and membership cards, are commonly shown by individuals in the form of certificates.

Bob

Show me your National

IdentificationDate of

BirthMother’s Name

Password

Bad Guy

4.3.1 Problems in Credential 4.3.1 Problems in Credential TransactionTransaction

Credential systems are subject to widespread abuse by individuals

Widespread use of highly secure identity documents providing links to centrally maintained credentials

Such as the modification and the copying of many kinds of paper ,plastic, and digital certificates

Are antithetical to the ability of individuals to determine how information about themselves is used

4.3.2 Solution for Credential Transaction 4.3.2 Solution for Credential Transaction (Using New Approach)(Using New Approach)

Individual takes a specially coded credential issued underone pseudonym

These coded credentials are maintained and shown onlyby individuals

Individuals can also tailor the coded form shown

And to transform it into a similarly coded form of the same credential that can be shown under the individual’s other pseudonyms

So that it provides only the necessary information and ensure that obsolete information become unlink able to current pseudonyms.

They provide control similar to that provided by certificates.

4.3.2.1 The Basic Credential 4.3.2.1 The Basic Credential SystemSystem

Carbon PaperEnvelope

2dD&^tvgS

Bob makes another one time userandom pseudonym. E.g 2dD&^tvgS

----------------------------

Slip

2dD&^tvgS

Bank

We need National Identity

and Address proof

Take one pseudonym . E.g. B2847dE forAll his credentials, such as, Address, Photo, National Identity, etc

Credential Issuing Organization

Give me National

Identity and Address

proof Credentials

for 2dD&^tvgS

B2847dE

Envelope

2dD&^tvgS

Bob

Thank Thank YouYou