TESLA Broadcast Authentication Protocol
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TESLA Broadcast Authentication Protocol

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What is one requirement for TESLA receivers regarding time synchronization?

  • They must be perfectly synchronized with the sender.
  • They must be completely unsynchronized.
  • They need to have real-time synchronization with external sources.
  • They need to be loosely synchronized with the sender. (correct)

    • How is a one-way chain generated according to the protocol?

  • By randomly selecting a starting point and applying a one-way function. (correct)
  • By using a symmetric encryption algorithm.
  • By applying a two-way function multiple times.
  • By generating a series of time-stamped values.

    • What is the purpose of using one-way chains in protocols?

  • To create a consensus among multiple receivers.
  • To ensure secure real-time communication.
  • To commit to a sequence of random values. (correct)
  • To encrypt messages with multiple keys.

    • What does TESLA need for authenticating keys at the receiver?

    <p>An efficient mechanism like one-way chains.</p> Signup and view all the answers

    In the context of a one-way chain, what role does s0 play?

    <p>It is a commitment to the entire one-way chain.</p> Signup and view all the answers

    What is the first use case mentioned for one-way chains?

    <p>One-time passwords by Lamport.</p> Signup and view all the answers

    What must not be strictly required by TESLA for time synchronization?

    <p>Complex time synchronization properties.</p> Signup and view all the answers

    What characteristic do one-way chains possess?

    <p>They allow verification of any element through a single commitment.</p> Signup and view all the answers

    What is required for the sender and receivers in the TESLA protocol?

    <p>They must be loosely time-synchronized.</p> Signup and view all the answers

    What does the sender do with each packet in the TESLA protocol?

    <p>Attaches a MAC computed over the packet contents.</p> Signup and view all the answers

    How does a receiver determine if the MAC key used for a packet is still secret?

    <p>It verifies the time interval of the sender.</p> Signup and view all the answers

    In what manner does the one-way chain function in TESLA?

    <p>It is used in reverse order of generation.</p> Signup and view all the answers

    What happens if the MAC key is found to be non-secret by the receiver?

    <p>The packet is discarded immediately.</p> Signup and view all the answers

    What does the sender provide in addition to the packet?

    <p>The most recent one-way chain value that can be disclosed.</p> Signup and view all the answers

    How is time divided in TESLA for key assignments?

    <p>In uniform intervals of duration $Tint$.</p> Signup and view all the answers

    What does buffering a packet by the receiver indicate in the context of TESLA?

    <p>The MAC key is still secret and undisclosed.</p> Signup and view all the answers

    What is the primary purpose of the nonce in the protocol?

    <p>To provide a random value that prevents replay attacks.</p> Signup and view all the answers

    Which key does the sender use to sign the response message sent to the receiver?

    <p>The private key KS−1.</p> Signup and view all the answers

    What does the receiver do immediately upon receiving the first message from the sender?

    <p>Verifies the digital signature and stores the sender time.</p> Signup and view all the answers

    How does the receiver compute the upper bound on the sender’s clock at the current local time t?

    <p>$t - tR + tS$.</p> Signup and view all the answers

    What does the real synchronization error after the protocol represent?

    <p>The upper limit on how much the sender's clock can differ.</p> Signup and view all the answers

    What does the receiver assume before starting the protocol?

    <p>A mechanism exists for verifying the sender’s public key.</p> Signup and view all the answers

    During which step does the receiver record its local time?

    <p>Before sending the first message.</p> Signup and view all the answers

    What information does the sender include in the message sent back to the receiver?

    <p>Sender's time and the random nonce.</p> Signup and view all the answers

    What is the purpose of using the one-way function F in the key chain?

    <p>To generate derived MAC keys</p> Signup and view all the answers

    How does the sender compute the MAC for packet Pj+3?

    <p>Using key Ki+1</p> Signup and view all the answers

    What action does a receiver take upon receiving the disclosed key Ki?

    <p>Check if it is known or if a later key Kj is available</p> Signup and view all the answers

    What is the key disclosure delay as indicated in the content?

    <p>2 time intervals</p> Signup and view all the answers

    What ensures the legitimacy of the received key Ki?

    <p>Verification against an earlier key Kv</p> Signup and view all the answers

    What is the main focus of time intervals as illustrated in the figure?

    <p>To create uniform timing for key generation</p> Signup and view all the answers

    What happens to keys as time progresses in the system shown?

    <p>Older keys may still be conveyed alongside new keys</p> Signup and view all the answers

    What is the significance of packets in time interval management?

    <p>They illustrate how keys correspond to specific packets</p> Signup and view all the answers

    What is the purpose of the receiver computing Ki = F(Ki)?

    <p>To verify packet authenticity</p> Signup and view all the answers

    What does the security of TESLA primarily depend on?

    <p>The computational intractability for attackers</p> Signup and view all the answers

    What is the relationship between key disclosure delay and network propagation delay in TESLA?

    <p>Key disclosure delay should not be much longer than network propagation delay.</p> Signup and view all the answers

    What assumption is made about the receiver's clock in the TESLA protocol?

    <p>It has a maximum error of ∆ and can be re-synchronized.</p> Signup and view all the answers

    What type of resistance does the function F provide in TESLA?

    <p>Weak collision resistance</p> Signup and view all the answers

    Which of the following is necessary for broadcast authentication in TESLA?

    <p>Asymmetric key encryption</p> Signup and view all the answers

    What role does the timestamping server play in the TESLA protocol?

    <p>It timestamps all TESLA packets it receives.</p> Signup and view all the answers

    What is required for nodes to trust the timestamping server in TESLA?

    <p>All nodes must be loosely synchronized and trust the server.</p> Signup and view all the answers

    What type of document does S.Haber and W.Stornetta propose a method for in their 1991 work?

    <p>Time-stamped documents</p> Signup and view all the answers

    Which aspect of network protocol does D.Mills focus on in his RFC 1305?

    <p>Time synchronization</p> Signup and view all the answers

    What year was the work 'Ariadne: A secure on-demand routing protocol for ad hoc networks' published?

    <p>2002</p> Signup and view all the answers

    Which protocol focuses on authentication using one-time passwords, according to N.Haller's 1992 work?

    <p>S/Key</p> Signup and view all the answers

    In which year was the discussion on 'How to sign digital streams' presented?

    <p>1997</p> Signup and view all the answers

    What is the primary focus of the work done by H.Lipmaa in their PhD thesis?

    <p>Secure and efficient time-stamping systems</p> Signup and view all the answers

    What was one of the main contributions of L.Lamport and P.Melliar-Smith in their 1985 work?

    <p>Fault tolerance in time synchronization</p> Signup and view all the answers

    Which conference proceedings include the work on 'IP multicast channels: EXPRESS support for large-scale single-source applications'?

    <p>ACM SIGCOMM</p> Signup and view all the answers

    Study Notes

    TESLA Broadcast Authentication Protocol

    •  Broadcast communication is becoming more popular for efficient data dissemination (e.g., satellite broadcasts, wireless radio broadcast, IP multicast)
    • A major challenge is source authentication: ensuring receivers can verify the source of broadcast data and that it hasn't been tampered with.
    • Traditional point-to-point authentication methods (using shared secret keys) aren't secure for broadcast because anyone with the secret key can forge packets.
    • TESLA (Timed, Efficient Stream Loss-tolerant Authentication) protocol addresses this, enabling receivers to verify the sender of broadcast packets.
    •  TESLA relies on loosely synchronized clocks between sender and receivers.
    •  It uses symmetric cryptography (message authentication codes - MACs) to authenticate packets.
    • The sender attaches a MAC to each packet, computed with a key only it knows.
    • The receiver buffers the packet.
    • Later, the sender discloses the key, allowing the receiver to authenticate the packet.
    • This protocol has low communication and computational overhead, scaling to large numbers of receivers.

    Time Synchronization

    • TESLA requires loosely synchronized clocks between sender and receivers.
    • Receivers only need an upper bound on the sender's clock.
    • This approach, outlined in the paper, doesn't require special infrastructure for synchronization.
    • The receiver needs an upper bound on the sender’s clock.

    One-Way Chains

    • One way chains are used to commit to a sequence of random values.
    • A one-way chain is a sequence of values, each derived from the previous one using a one-way hash function.
    •  The sender computes the chain and reveals values in a specific order.
    • The receiver can verify elements of the chain.
    •  This method provides commitments without revealing the entire one-way chain.

    TESLA Protocol Details

    • The sender divides time into uniform intervals.
    • A key from a one-way chain is assigned to each interval (one key per time interval).
    • The sender computes a MAC for each packet using the key from the corresponding interval that it will disclose later.
    • The sender discloses keys corresponding to a certain time interval.
    • The receiver checks if the disclosed keys are safe and verify the MAC of the buffered packets.

    Security Considerations

    • TESLA relies on the assumption that receivers and senders are loosely time synchronized with an upper bound on difference.
    • Receivers periodically resynchronize their clocks.
    • The protocol uses secure PRFs (Pseudo-Random Functions).
    • Weak collision resistance is important for the protocol's security.

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    Related Documents

    TESLA Broadcast Authentication Protocol PDF

    Description

    Explore the TESLA protocol designed for source authentication in broadcast communications. This quiz covers the challenges of verifying broadcast packet sources and how TESLA utilizes symmetric cryptography to secure data transmission. Test your understanding of efficient authentication methods and the significance of time synchronization in this context.

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