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COEN 351

COEN 351. Authentication. Authentication. Authentication is based on What you know Passwords, Pins, Answers to questions, … What you have (Physical) keys, tokens, smart-card What you are Biometrics: fingerprints, Iris, voice, … Where you are IP-address (not very secure), …

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COEN 351

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  1. COEN 351 Authentication

  2. Authentication • Authentication is based on • What you know • Passwords, Pins, Answers to questions, … • What you have • (Physical) keys, tokens, smart-card • What you are • Biometrics: fingerprints, Iris, voice, … • Where you are • IP-address (not very secure), … • Who else trusts you • Certification by trusted third party, …

  3. Authentication • Passwords, Pins, … threatened by • External disclosure • Looking over the shoulder, social engineering • Guessing • Brute forcing, dictionary attack, … • Snooping • Finds unencrypted passwords • Circumvention through replay • Host compromise • That hands out password file.

  4. Authentication • Password protection mechanisms • Transformation: Password presented by user to client is hashed, hash is sent to server. Server compares with hash of password. • UNIX Salting: Each hash is different. • Challenge-response • Protects against replay attacks. • Time stamps • Authentication request from client to server depends on time. • Protects against replays. • One-time passwords • Digital Signature with every request. • Zero-Knowledge techniques

  5. Authentication Kerberos: • Authentication system based on symmetric cryptography • For patent reasons

  6. Kerberos • Every user / client / server shares a key with the authentication server. • Authentication server hands out tickets to all other servers.

  7. Kerberos • First exchange between user and Authentication Server establishes a session key. • This way, the same key is used only sparingly.

  8. Key Distribution Center • KDC: • Database of keys for all users • Invents and hands out keys for each transaction between clients. Alice KDC Bob Alice wants Bob KAlice{ KAB for Bob } KBob{KAB for Alice}

  9. Personal Tokens • Small hardware devices that use a pin to unlock. • Storage Token: contains a secret value. • Synchronous one-time password generator • Generates a new password once a minute. • Challenge Response: • Implements the calculation of the response from a challenge according to a secret algorithm. • Digital Signature Token: • Calculates digital signature from message MAC.

  10. Personal Tokens • Human Interface Token. • Handheld with digital display (and keyboard). • Smartcard • Dimensions and contacts standardized by ISO/IEC. • PCMCIA card • USB token

  11. Biometrics • Fingerprint recognition • Voice recognition • Handwriting recognition • Face recognition • Retinal scan • Hand geometry recognition

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