CSCE 522 Identification and Authentication

CSCE Farkas2Reading Reading for this lecture: Required: – Pfleeger: Ch. 4.5, Ch. 4.3 Kerberos – An Introduction to Computer Security: The NIST Handbook, : Chapter 16, Identification and Authentication, pages Recommended: – Smart Card Alliance, – Securing Digital Identities & Information, strong authentication – Certificate Authority GlobalSign Loses Critical Data to ComodoHacker, data-leak.html, Sept 8, data-leak.html Reading for next lecture: – Pfleeger: Ch. 4.3 and 4.4

Identification Establishes the identity of an individual/system/ap- plication/etc. Proof of identity: password, driver’s license, Id card, etc. CSCE Farkas3

4 Authentication Allows an entity (a user or a system) to prove its identity within a context, e.g., computer system Typically, the entity whose identity is verified reveals knowledge of some secret S to the verifier Strong authentication: the entity reveals knowledge of S to the verifier without revealing S to the verifier

CSCE Farkas5 Authentication Information Must be securely maintained by the system.

CSCE Farkas6 Elements of Authentication Person/group/code/system: to be authenticated Distinguishing characteristics: differentiates the entities to be authenticated Proprietor/system owner/administrator: responsible for the system Authentication mechanism: verify the distinguishing characteristics Access control mechanism: grant privileges upon successful authentication

CSCE Farkas7 Authentication Requirements Network must ensure – Data exchange is established with addressed peer entity not with an entity that masquerades or replays previous messages Network must ensure data source is the one claimed Authentication generally follows identification – Establish validity of claimed identity – Provide protection against fraudulent transactions

CSCE Farkas8 User Authentication What the user knows – Password, personal information What the user possesses – Physical key, ticket, passport, token, smart card What the user is (biometrics) – Fingerprints, voiceprint, signature dynamics

CSCE Farkas9 Passwords Commonly used method For each user, system stores (user name, F(password)), where F is some transformation (e.g., one-way hash) in a password file – F(password) is easy to compute – From F(password), password is difficult to compute – Password is not stored in the system When user enters the password, system computes F(password); match provides proof of identity

CSCE Farkas10 Vulnerabilities of Passwords Inherent vulnerabilities – Easy to guess or snoop – No control on sharing Practical vulnerabilities – Visible if unencrypted in distributed and network environment – Susceptible for replay attacks if encrypted naively Password advantage – Easy to modify compromised password.

CSCE Farkas11 Attacks on Password Guessing attack/dictionary attack Social Engineering Sniffing Trojan login Van Eck sniffing

CSCE Farkas12 Guessing Attack Exploits human nature to use easy to remember passwords Trial-and-error attack Easy to detect (failed logins) and block – Problem: if the attacker has access to the password file (even if it is encrypted) Need audit mechanism

CSCE Farkas13 Social Engineering Attacker asks for password by masquerading as somebody else (not necessarily an authenticated user) May be difficult to detect Protection against social engineering: strict security policy and users’ education

CSCE Farkas14 Dictionary Attacks on Passwords Attack 1: – Create dictionary of common words and names and their simple transformations – Use these to guess password Attack 2: – Usually F is public and so is the password file (encrypted) – Compute F(word) for each word in dictionary – Find match

CSCE Farkas15 Password Salt Used to make dictionary attack more difficult Salt is a 12 bit number between 0 and 4095 It is derived from the system clock and the process identifier Compute F(password+salt); both salt and F(password+salt) are stored in the password table User: gives password, system finds salt and computes F(password+salt) and check for match Better!: use a random number, user authenticates by sending F(password+random number) || random number

CSCE Farkas16 Password Management Policy Educate users to make better choices Define rules for good password selection and ask users to follow them Ask or force users to change their password periodically Actively attempt to break user’s passwords and force users to change broken ones Screen password choices

CSCE Farkas17 One-time Password Use the password exactly once! The first use of the password would grant access; a second or subsequent use of the same password would not

CSCE Farkas18 Lamport’s scheme Doesn’t require any special hardware System computes one-way function F, such as F(x),F 2 (x),…, F 1000 (x) System stores user’s name and F 1000 (x) User supplies F 999 (x) the first time If the login is correct, system replaces F 1000 (x) with F 999 (x) Next login: user supplies F9 98 (x) … and so on User calculates F n (x) using a hand-held calculator, a workstation, or other devices

CSCE Farkas19 Time Synchronized There is a hand-held authenticator – It contains an internal clock, a secret key, and a display – Display outputs a function of the current time and the key – It changes about once per minute User supplies the user id and the display value Host uses the secret key, the function and its clock to calculate the expected output Login is valid if the values match

CSCE Farkas20 Time Synchronized Secret key Time One Time Password DES Problem: Need time synchronization between device and server

CSCE Farkas21 Challenge Response Work station Host Network Non-repeating challenges from the host is used The device requires a keypad User ID Challenge Response

CSCE Farkas22 Challenge Response Secret key Challenge One Time Password DES

CSCE Farkas23 Devices with Personal Identification Number (PIN) Devices are subject to theft, some devices require PIN (something the user knows) PIN is used by the device to authenticate the user Problems with challenge/response schemes – Key database is extremely sensitive – This can be avoided if public key algorithms are used

CSCE Farkas24 Smart Cards Portable devices with a CPU, I/O ports, and some nonvolatile memory Can carry out computation required by public key algorithms and transmit directly to the host Some use biometrics data about the user instead of the PIN

CSCE Farkas25 Biometrics Fingerprint Retina scan Voice pattern Signature Typing style

CSCE Farkas26 Problems with Biometrics Expensive – Retina scan (min. cost) about $ 2,200 – Voice (min. cost) about $ 1,500 – Signature (min. cost) about $ 1,000 False readings – Retina scan 1/10,000,000+ – Signature 1/50 – Fingerprint 1/500 Can’t be modified when compromised

Identity Management Distributed, heterogeneous domain User credentials Performance CSCE Farkas27 I am Ann. Here is my Password1. System 1 System 3 System 2 I am Ann. Here is my Password2. I am Ann. Here is my Password3. pswd

Identity Management cont. Need verifiable proof of identity – without being authenticated during every single interaction Digital certificate: links identity and public key together – A user can prove his/her identity by signing the messages with his/her private key CSCE Farkas28

Digital Certificates Most common digital certificate: X.509 Initially issued in 1988 Rely on PKI and hierarchy of certificate authorities Certificate Authority: issue and revoke digital certificates, accepts user notifications, publishes revocation list CSCE Farkas29

Digital Certificates Basic Content – … – Issuer – Validity Not Before Not After – Subject – Subject Public Key Info Public Key Algorithm Subject Public Key – … – Certificate Signature Algorithm – Certificate Signature CSCE Farkas30

Problem with X.509 Large file Long duration  needs validation of certificate for revocation Why are digital certificates revoked? – Exposure of private key – Incorrect/unauthorized issuance – Termination of assignment CSCE Farkas31

Return to Multiple Authentication CSCE Farkas32 I am Ann. Here is my X.509 System 1 System 3 System 2 I am Ann. Here is my X.509 I am Ann. Here is my X.509 CA Verify Certificate

Single Sign On CSCE Farkas33 I am Ann. Here is my X.509. Give me a locally verifiable token. System 1 System 3 System 2 I am Ann. Here is my SAML token I am Ann. Here is my SAML token SAML token CA Verify Certificate

CSCE Farkas34 Next Class Access Control