Authentication Advanced Software Engineering (CSE870)

Instructor: Dr. B. ChengContact info: chengb at cse dot msu dot edu

Authentication Advanced Software Engineering (CSE870)

Instructor: Dr. B. ChengContact info: chengb at cse dot msu dot edu

Eduardo Diaz

Dan Fiedler

Andres Ramirez

Eduardo Diaz

Dan Fiedler

Andres Ramirez

Road MapRoad Map

Introduction to Authentication Needham-Schroeder, Otway-Rees, Kerberos

Commonalities Additional Requirements Class Diagrams State Diagrams Conclusions

Introduction to Authentication Needham-Schroeder, Otway-Rees, Kerberos

Commonalities Additional Requirements Class Diagrams State Diagrams Conclusions

AuthenticationAuthentication

Meet: Alice (Staff)

Bob (MISys)

Meet: Alice (Staff)

Bob (MISys)

AuthenticationAuthentication

Purpose Key exchange.

Allow Alice to secretly communicate with Bob using a shared cryptographic key.

Methods Private keys, shared keys, public keys…

Potential Problems Trustworthy? Safe handling of private keys?

Purpose Key exchange.

Allow Alice to secretly communicate with Bob using a shared cryptographic key.

Methods Private keys, shared keys, public keys…

Potential Problems Trustworthy? Safe handling of private keys?

Needham-SchroederNeedham-Schroeder

1. Alice Cathy: {Alice || Bob || rand1}

2. Cathy Alice: {Alice || Bob || rand1}Ksess

|| {Alice || Ksess}kbob}kalice

3. Alice Bob: {Alice || ksess}kbob

4. Bob Alice: {rand2}ksess

5. Alice Bob: {rand2 - 1}ksess

1. Alice Cathy: {Alice || Bob || rand1}

2. Cathy Alice: {Alice || Bob || rand1}Ksess

|| {Alice || Ksess}kbob}kalice

3. Alice Bob: {Alice || ksess}kbob

4. Bob Alice: {rand2}ksess

5. Alice Bob: {rand2 - 1}ksess

Needham SchroederNeedham Schroeder

Motive? Prevent replay attacks

A valid data transmission is retransmitted maliciously.

Nonces Randomly generated numbers to identify

exchanges. Key idea: Cathy is trusted by Alice and

Bob.

Motive? Prevent replay attacks

A valid data transmission is retransmitted maliciously.

Nonces Randomly generated numbers to identify

exchanges. Key idea: Cathy is trusted by Alice and

Bob.

Otway-ReesOtway-Rees

1. Alice Bob: num || Alice || Bob || { rand1 || num || Alice|| Bob}kalice

2. Bob Cathy: num || Alice || Bob ||

{rand1 || num || Alice || Bob}kalice || {rand2 || num || Alice || Bob}kbob

3. Cathy Bob: num || {rand1 || ksess}kalice || {rand2 || ksess}kbob

4. Bob Alice: num || {rand1 || ksess}kalice

1. Alice Bob: num || Alice || Bob || { rand1 || num || Alice|| Bob}kalice

2. Bob Cathy: num || Alice || Bob ||

{rand1 || num || Alice || Bob}kalice || {rand2 || num || Alice || Bob}kbob

3. Cathy Bob: num || {rand1 || ksess}kalice || {rand2 || ksess}kbob

4. Bob Alice: num || {rand1 || ksess}kalice

Otway-ReesOtway-Rees

Motivation Needham-Schroeder assumes all cryptographic

keys are secure… in practice generated pseudorandomly… but it can be predicted.

Num Verify that num agrees through the exchanges.

Key Idea Cathy is again the trustworthy element.

Motivation Needham-Schroeder assumes all cryptographic

keys are secure… in practice generated pseudorandomly… but it can be predicted.

Num Verify that num agrees through the exchanges.

Key Idea Cathy is again the trustworthy element.

KerberosKerberos

1. Alice Cerberus: Alice || Barnum

2. Cerberus Alice: {kalice,barnum}kalice || Talice,barnum

3. Alice Barnum: Guttenberg || Aalice,barnum ||

Talice,barnum

1. Barnum Alice: Alice || {kalice,guttenberg}kalicebarnum

|| Talice,guttenberg

1. Alice Guttenberg: Aalice,guttenberg ||

Talice,guttenberg

6. Guttenberg Alice: {t+1}kalice,guttenberg

1. Alice Cerberus: Alice || Barnum

2. Cerberus Alice: {kalice,barnum}kalice || Talice,barnum

3. Alice Barnum: Guttenberg || Aalice,barnum ||

Talice,barnum

1. Barnum Alice: Alice || {kalice,guttenberg}kalicebarnum

|| Talice,guttenberg

1. Alice Guttenberg: Aalice,guttenberg ||

Talice,guttenberg

6. Guttenberg Alice: {t+1}kalice,guttenberg

KerberosKerberos

What is T? Talice,barnum = Barnum || {Alice || Alice Address ||

valid time || kalice,barnum}kbarnum

What is A? {Alice || generation time || kt}kalice,barnum

Kt… not used.

What is T? Talice,barnum = Barnum || {Alice || Alice Address ||

valid time || kalice,barnum}kbarnum

What is A? {Alice || generation time || kt}kalice,barnum

Kt… not used.

KerberosKerberos

Motivation Separate authentication of the user to ticket granting

server and resource being requested.

2 Servers Authenticate first Obtain ticket second

Key Idea: Time windows Separation of trusted parties

Motivation Separate authentication of the user to ticket granting

server and resource being requested.

2 Servers Authenticate first Obtain ticket second

Key Idea: Time windows Separation of trusted parties

CommonalitiesCommonalities

Message Passing Authentication Requests Encryption / Decryption Key Passing … other than that, not much!

Each protocol has slight variants.

Message Passing Authentication Requests Encryption / Decryption Key Passing … other than that, not much!

Each protocol has slight variants.

Additional RequirementsAdditional Requirements

Same as other groups plus: Incorporate 2 design patterns

1 must be a security design pattern Strategy Design Pattern (encryption algorithms) Single Access Point (entry and logging)

Instantiate the framework at MISys At the whitebox level

Same as other groups plus: Incorporate 2 design patterns

1 must be a security design pattern Strategy Design Pattern (encryption algorithms) Single Access Point (entry and logging)

Instantiate the framework at MISys At the whitebox level

Whitebox Class DiagramWhitebox Class Diagram

N.S. Class DiagramN.S. Class Diagram

O.R. Class DiagramO.R. Class Diagram

Kerberos Class DiagramKerberos Class Diagram

Whitebox Class Diagram-MISysWhitebox Class Diagram-MISys

State Diagrams, NSState Diagrams, NS

State Diagrams, N.S.State Diagrams, N.S.

State Diagram, O.R.State Diagram, O.R.

State Diagram, O.R.State Diagram, O.R.

State Diagram, KerberosState Diagram, Kerberos

Graybox Class DiagramGraybox Class Diagram

BlackBox Class DiagramBlackBox Class Diagram

ConclusionsConclusions

Questions? Questions?