Trusted Protected Module TPM 2.0 Challenge-Response Authentication

Trusted Protected Module (TPM) version 2.0 challenge-response protocols use cryptographic methods to prove the identity of a user or system and authorize sensitive operations. Instead of relying on a shared, static secrets like a password, the protocols use a dynamic exchange to prevent replay attacks and secure key-based operations.

Jay.Mayers@optioauth.io

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Table of Contents

1 - TPM 2.0 Challenge-Response TTP

2 - TPM 2.0 Challenge-Response Protocols

3 - TPM 2.0 HMAC Authorization Sessions

4 - TPM 2.0 Remote Attestation

5 - TPM 2.0 Policy-Based Authorization Data Sealing

6 - TPM 2.0 Challenge-Response Benefits

7 - TPM 2.0 Benefits for Authentication and Access control

8 - TPM 2.0 Benefits for System and Data Integrity

9 - TPM 2.0 Benefits of Hardware-Based Security

10 - TPM 2.0 Benefits of Software-Based Security

11 - TPM 2.0 Challenge-Response Authentication Quiz (1 - 25 )

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1 - TPM 2.0 Challenge-Response TTP

A challenge-response protocol has two main components:

1.1 - The Challenger (Verifier): An entity, like a remote server, that issues a unique "challenge."

1.2 - The Claimant (Provider or Attestor): TPM-enabled entity system that uses cryptographic keys to generate a valid "response" based on the challenge from the Verifier.

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2 - TPM 2.0 Challenge-Response Protocols

TPM 2.0 supports challenge-response protocols through several mechanisms, primarily centered on its ability to perform cryptographic operations using keys and secrets that never leave the security of the TPM itself. By performing the "response" computation within the TPM, it proves to a "challenger" that the system possesses the corresponding private key or secret.

The main challenge-response techniques supported by TPM 2.0 include:

2.1 - HMAC Authorization

2.2 - Remote Attestation

2.3 - Policy-Based Authorization

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3 - TPM 2.0 HMAC Authorization Sessions

This method uses a Hash-based Message Authentication Code (HMAC) to perform a secure challenge-response authentication for access to a TPM-protected device or entity.

3.1 - Challenge: A remote challenger (Verifier) sends a session nonce (random hash value) to the system (Attestor). The local application, acting on behalf of the challenger, then uses the TPM to set up an HMAC authorization session with the target object.

3.2 - Response: The (Attestor) TPM uses the object's secret authorization value and the challenge nonce to compute an HMAC. This response is a proof of possession of the secret, and it is passed to the challenger (Verifier).

3.3 - Verification: The challenger (Verifier) performs the same computation and verifies that the response from the TPM-equipped (Attestors) system is correct. Since the HMAC secret never leaves the TPM, a correct response proves cryptographically that the system possesses the correct key.

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4 - TPM 2.0 Remote Attestation

Remote (TPM2_Quote) attestation is a formal challenge-response process where a remote Verifier validates the integrity and identity of a Attestors TPM device.

4.1 - Verifier Challenge: A verifier sends a random nonce as a challenge to an attesting device.

4.1.1 - The verifier  specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify.

4.1.2 - PCRs are cryptographic registers that contain measurements of a system's boot-up and runtime state.

4.2 - Attestor Response: The Attestors TPM computes a digest of the selected PCR values.

4.2.1 - The Assetors TPM signs the digest, along with the Verifiers nonce using a special Attestation Identity Key (AIK) .

4.2.2 - This signature is called a "quote" and returns this digitally signed quote to the verifier.

4.3 - Verifier Verification:  The verifier uses the attestors TPM's public key to check the signature on the quote. A valid signature proves two things:

4.3.1 - The quote was signed by a legitimate TPM.

4.3.2 - The signed PCR values from the boot process have not been tampered.

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5 - TPM 2.0 Policy-Based Authorization Data Sealing

Policy-based authorization (TPM2_PolicySigned) method allows a sensitive data to be "sealed" within the TPM. This is an advanced protocol that allows for complex authorization rules. It is often used to seal (encrypt) data to a specific TPM and only unseal it under certain conditions.

5.1 - Seal: A piece of data is sealed to the TPM, and a specific set of PCR values is chosen to create an access policy. The TPM will only unseal the data if the current PCRs match the values in the policy.

5.2 - Challenge: When a process requests the unsealing, the TPM internally "challenges" the system's current state by comparing the live PCR values to the sealed-in policy values.

5.3 - Response: If the comparison is successful, the TPM unseals the data and releases it to the requesting application. If the PCRs have changed due to an unauthorized software modification, the challenge fails and the data remains encrypted within the TPM. This creates a powerful challenge-response mechanism for data access bound to system integrity.

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6 - TPM 2.0 Challenge-Response Benefits

TPM 2.0 challenge-response protocols provides a hardware-backed method for verifying a device's identity and integrity, offering stronger security than software-only solutions. These essential protocols are a key component of remote attestation, a process that ensures a device has not been tampered with before granting it access to a network or sensitive data.

6.1 - Benefits for system and data integrity

6.2 - Benefits for authentication and access control

6.3 - Benefits over hardware-based security

6.4 - Benefits over software-based security

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7 - TPM 2.0 Benefits for Authentication and Access control

TPM 2.0 challenge-response protocols provides a hardware-backed method for verifying a device's identity and integrity, offering stronger security than software-only solutions. These essential protocols are a key component of remote attestation, a process that ensures a device has not been tampered with before granting it access to a network or sensitive data.

7.1 - Prevent replay attacks: The use of a nonce (a one-time, unpredictable number) ensures that an attacker cannot simply record a successful challenge-response and replay it later to gain unauthorized access.

7.2 - Bind keys to hardware: These protocols enforce that sensitive keys can only be used by the specific, trusted hardware (the TPM), protecting them from software-based attacks.

7.3 - Secure remote authentication: By providing cryptographically verifiable proof of a system's hardware and software state, these protocols enable secure remote authentication for managing networked devices.

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8 - TPM 2.0 Benefits for System and Data Integrity

TPM 2.0 significantly enhances system and data integrity by providing a hardware-based "root of trust" that protects against software vulnerabilities and physical tampering by isolating critical security functions in a dedicated chip.

8.1 - Proof of device identity: When a TPM 2.0-enabled device attempts to connect to a network, it can use its unique endorsement key (EK) to prove its identity during the challenge-response sequence. This prevents unauthorized or spoofed devices from gaining access.

8.2 - Verification of device integrity: During a measured boot process, the system's firmware and bootloaders measure their own state by generating cryptographic hashes, which are stored in the TPM's Platform Configuration Registers (PCRs). The challenge-response protocol can then generate a signed "quote" of these PCR values. This quote can cryptographically verify that the device's boot sequence and software stack have not been compromised.

8.3 - Tamper evidence: If an attacker modifies any component of the boot process, the resulting TPM2 PCR values will not match the expected values. The signed quote will prove this discrepancy, providing strong evidence of tampering that cannot be erased or hidden a attacker.

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9 - TPM 2.0 Benefits of Hardware-Based Security

Hardware-based security with Trusted Platform Module 2.0 (TPM2) provides a root of trust for your system, protecting it from both software and physical attacks. A TPM is a dedicated, tamper-resistant chip—either on the motherboard or integrated into the CPU—that safeguards sensitive data like encryption keys, certificates, and passwords in a secure vault.

9.1 - Hardware root of trust: The TPM acts as a hardware root of trust, meaning it is implicitly trusted and isolated from the main system. This provides a higher level of security than software alone, which is vulnerable to attacks on the operating system.

9.2 - Protection against physical attacks: TPMs are designed to be tamper-resistant. They resist physical attacks, such as probing the chip, to prevent unauthorized access to the cryptographic keys and sensitive data stored inside.

9.3 - Secure key management: The TPM's secure environment prevents cryptographic keys from being copied or used outside of the module. This protects sensitive information from malware and other software-based attacks, even if the system is compromised.

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10 - TPM 2.0 Benefits of Software-Based Security

TPM2 software-based (vTPM or fTPM) security, often in the form of an emulator, offers critical benefits for developers, virtualized environments, and testing purposes. It provides a flexible and accessible way to work with the TPM2 features in virtual machine and cloud-based deployments.  All Cloud environments are Software-Base TPM 2.0. 

10.1 - Credential protection: Software TPMs can help protect user credentials through features like OptioAuth with OptioCon Authenticator Agent.

10.2 - Isolation: Authentication and Validation functions run in a protected Trusted Execution Environment (TEE).  A TEE is a secure, isolated area within a device's main processor that protects code and data from the rest of the system, ensuring confidentiality and integrity. Instead of a separate hardware chip, a software-based TEE "containerized" fTPM is accessed.  

10.3 - Root of Trust: Stronger than software-only. A software vTPM or fTPM still provides stronger root of trust than a pure software-only solution when leveraged by TEE.

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11 - TPM 2.0 challenge-response (25) Quiz Questions

If you want to walk the walk, you’ve got to talk the talk. The Quiz answers are based solely on the content from this TTP training module.  Answers and explanations provided after the Quiz.

Cheers and Good Luck - OptioAuth Team

TPM 2.0 challenge-response Quiz (1 - 25 )

11.1 - What is a TPM?

1. Total Protection Module

2. Trusted Protected Module

3. Transient Platform Module

4. Trusted Platform Module

TPM 2.0 challenge-response Quiz (2 - 25 )

11.2 - What are two main components of TPM 2.0 challenge-response protocol (Pick two)?

1. The Claimant (Provider or Attestor) of a TPM-enabled entity system.

2. The HMAC authorization session

3. The Challenger (Verifier) entity, like a remote server

4. The TPM Platform Configuration Register

TPM 2.0 challenge-response Quiz (3 - 25 )

11.3  - What are the two TPM 2.0 challenge-response Protocols?

1. HMAC Authorization, Remote Attestation

2. The Challenger (Verifier), The Claimant (Attestor)

3. The Inner TPM 2.0 Policy, The Key Sealing 

4. Create Endorsement Key, Verify Signature

TPM 2.0 challenge-response Quiz (4 - 25 )

11.4 - What are two roles of the TPM 2.0 HMAC Authorization Challenge Verifier (Pick Two)?

1. Performs the same computation as the attestor and verifies that the response from the TPM-equipped (Attestors) system is correct

2. Uses the object's secret authorization value and the challenge nonce to compute an HMAC.

3. Sends a session nonce (random hash value) to the system (Attestor)

4. Uses the TPM to set up an HMAC authorization session with the target object.

TPM 2.0 challenge-response Quiz (5 - 25 )

11.5 - What are two roles of the TPM 2.0 HMAC Authorization Attestor (Pick Two)?

1. Performs the same computation as the attestor and verifies that the response from the TPM-equipped (Attestors) system is correct

2. Uses the object's secret authorization value and the challenge nonce to compute an HMAC.

3. Sends a session nonce (random hash value) to the system (Attestor)

4. Uses the TPM to set up an HMAC authorization session with the target object.

TPM 2.0 challenge-response Quiz (6 - 25 )

11.6 - What are two roles of the TPM 2.0 Remote Attestation Attestor (Pick Two)?

1. Signs the digest, along with the Verifiers nonce using a special Attestation Identity Key (AIK) .

2. Check the signature on the quote to prove was signed by a legitimate TPM

3. Computes a digest of the selected PCR values.

4. Specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify.

TPM 2.0 challenge-response Quiz (7 - 25 )

11.7 - What are two roles of the TPM 2.0 Remote Attestation Verifier (Pick Two)?

1. Signs the digest, along with the Verifiers nonce using a special Attestation Identity Key (AIK) .

2. Check the signature on the quote to prove was signed by a legitimate TPM

3. Computes a digest of the selected PCR values.

4. Specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify.

TPM 2.0 challenge-response Quiz (6 - 25 )

11.6 - What is the purpose of TPM 2.0 Policy-Based Authorization Data Sealing (Pick Two)?

1. Used to seal (encrypt) data to a specific TPM and only unseal it under certain conditions

2. To create a signature "quote" and return this digitally signed quote to the verifier.

3. Allows a sensitive data to be "sealed" within the TPM.

4. Used to send a session nonce (random hash value) to the system (Attestor)

TPM 2.0 challenge-response Quiz (7 - 25 )

11.7 - What is the role of the TPM 2.0 Policy-Based Authorization Data Sealing Challenge?

1. When a process requests the unsealing, the TPM internally "challenges" the system's current state by comparing the live PCR values to the sealed-in policy values.

2. A piece of data is sealed to the TPM, and a specific set of PCR values is chosen to create an access policy

3. If the comparison is successful, the TPM unseals the data and releases it to the requesting application.

4. Specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify.

TPM 2.0 challenge-response Quiz (8 - 25 )

11.8 - What is the role of the TPM 2.0 Policy-Based Authorization Data Sealing Response?

1. When a process requests the unsealing, the TPM internally "challenges" the system's current state by comparing the live PCR values to the sealed-in policy values.

2. A piece of data is sealed to the TPM, and a specific set of PCR values is chosen to create an access policy

3. If the comparison is successful, the TPM unseals the data and releases it to the requesting application.

4. Specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify.

TPM 2.0 challenge-response Quiz (9 - 25 )

11.9 - What are the TPM 2.0 Challenge-Response Benefits?

1. User control over which attestations are linked by a specific verifier, while still maintaining overall anonymity.

2. System and Data Integrity, Authentication and Access Control, Hardware and Software Based Security.

3. User Privacy & Anonymity allows a platform to authenticate itself without revealing its identity, ensuring that a verifier cannot link consecutive attestations from the same device to a specific user.

4. Provides a Private Endorsement Key (EK) to be used for PKI encryption

TPM 2.0 challenge-response Quiz (10 - 25 )

11.10 - What are two TPM 2.0 Benefits for Authentication and Access control (Pick Two)?

1. User control over which attestations are linked by a specific verifier, while still maintaining overall anonymity.

2. Secure remote authentication by providing cryptographically verifiable proof of a system's hardware and software state, these protocols enable secure remote authentication for managing networked devices.

3. Protect against all types of Cyberattacks, malicious software, ransomware or trojans,

4. Prevent replay attacks with use of a nonce (a one-time, unpredictable number) ensures that an attacker cannot simply record a successful challenge-response and replay it later to gain unauthorized access.

TPM 2.0 challenge-response Quiz (11 - 25 )

11.11 - What are the core TPM 2.0 Benefits for Authentication and Access control (Pick One)?

1. Proof of device identity, Verification of device integrity, Tamper evidence

2. Prevent replay attacks, Bind keys to hardware and Secure remote authentication

3. Credential protection, Isolation: Authentication and Validation and Root of Trust

4. Hardware root of trust, Protection against physical attacks and Secure key management

TPM 2.0 challenge-response Quiz (12 - 25 )

11.12 - How does TPM 2.0 Authentication and Access Control prevent replay attacks (Pick One)?

1. A piece of data is sealed to the TPM, and a specific set of PCR values is chosen to create an access policy.

2. The use of a nonce (a one-time, unpredictable number) ensures that an attacker cannot simply record a successful challenge-response and replay it later to gain unauthorized access.

3. The verifier specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify

4. Provides a Private Endorsement Key (EK) to be used for PKI encryption

TPM 2.0 challenge-response Quiz (13 - 25 )

11.13 - What is the purpose of TPM 2.0 Authentication and Access Control binding keys to hardware (Pick One)?

1. To provide cryptographically verifiable proof of a system's hardware and software state.

2. The use of a nonce (a one-time, unpredictable number) ensures that an attacker cannot simply record a successful challenge-response and replay it later to gain unauthorized access.

3. Enforces as unique endorsement key (EK) to prove its identity during the challenge-response sequence.

4. Enforces sensitive keys can only be used by the specific, trusted hardware (the TPM), protecting them from software-based attacks.

TPM 2.0 challenge-response Quiz (14 - 25 )

11.14 - What is the purpose of TPM 2.0 Authentication and Access Control Secure remote authentication (Pick One)?

1. To provide a cryptographically verifiable proof of a system's hardware and software state, these protocols enable secure remote authentication for managing networked devices.

2. The use of a nonce (a one-time, unpredictable number) ensures that an attacker cannot simply record a successful challenge-response and replay it later to gain unauthorized access.

3. Enforces as unique endorsement key (EK) to prove its identity during the challenge-response sequence.

4. Enforces sensitive keys can only be used by the specific, trusted hardware (the TPM), protecting them from software-based attacks.

TPM 2.0 challenge-response Quiz (15 - 25 )

11.15 - What are the core TPM 2.0 Benefits for System and Data Integrity (Pick One)?

1. Proof of device identity, Verification of device integrity, Tamper evidence

2. Prevent replay attacks, Bind keys to hardware and Secure remote authentication

3. Credential protection, Isolation: Authentication and Validation and Root of Trust

4. Hardware root of trust, Protection against physical attacks and Secure key management

TPM 2.0 challenge-response Quiz (16 - 25 )

11.16 - What is TPM 2.0 System and Data Integrity Proof of Device Identity (Pick One)?

1. Protects sensitive information from malware and other software-based attacks, even if the system is compromised.

2. Acts as a hardware root of trust, meaning it is implicitly trusted and isolated from the main system

3. TPM 2.0-enabled device attempts to connect to a network, it can use its unique endorsement key (EK) to prove its identity during the challenge-response sequence.

4. During a measured boot process, the system's firmware and bootloaders measure their own state by generating cryptographic hashes

TPM 2.0 challenge-response Quiz (17 - 25 )

11.17 - What is TPM 2.0 System and Data Integrity Verification of device integrity (Pick One)?

1. Protects sensitive information from malware and other software-based attacks, even if the system is compromised.

2. Provides cryptographically verifiable proof of a system's hardware and software state, these protocols enable secure remote authentication for managing networked devices.

3. TPM 2.0-enabled device attempts to connect to a network, it can use its unique endorsement key (EK) to prove its identity during the challenge-response sequence.

4. During a measured boot process, the system's firmware and bootloaders measure their own state by generating cryptographic hashes.

TPM 2.0 challenge-response Quiz (18 - 25 )

11.18 - What are the core TPM 2.0 Benefits for Hardware-Based Security (Pick One)?

1. Proof of device identity, Verification of device integrity, Tamper evidence

2. Prevent replay attacks, Bind keys to hardware and Secure remote authentication

3. Credential protection, Isolation: Authentication and Validation and Root of Trust

4. Hardware root of trust, Protection against physical attacks and Secure key management

TPM 2.0 challenge-response Quiz (19 - 25 )

11.19 - What is TPM 2.0 Hardware-Based Hardware Root of Trust (Pick One)?

1. Provides cryptographically verifiable proof of a system's hardware and software state, these protocols enable secure remote authentication for managing networked devices.

2. The TPM acts as a hardware root of trust, meaning it is implicitly trusted and isolated from the main system

3. Enforces sensitive keys can only be used by the specific, trusted hardware (the TPM), protecting them from software-based attacks.

4. Provides a Private Endorsement Key (EK) to be used for PKI encryption

TPM 2.0 challenge-response Quiz (20 - 25 )

11.20 - How does TPM 2.0 Hardware-Based Hardware Protection against physical attacks (Pick One)?

1. Provides cryptographically verifiable proof of a system's hardware and software state, these protocols enable secure remote authentication for managing networked devices.

2. Provides Isolation Authentication and Validation functions run in a protected Trusted Execution Environment (TEE)

3. Enforces sensitive keys can only be used by the specific, trusted hardware (the TPM), protecting them from software-based attacks.

4. They resist physical attacks, such as probing the chip, to prevent unauthorized access to the cryptographic keys and sensitive data stored inside.

TPM 2.0 challenge-response Quiz (21 - 25 )

11.21 - What is the purpose of TPM 2.0 Hardware-Based Security Secure key management (Pick One)?

1. The TPM's secure environment prevents cryptographic keys from being copied or used outside of the module.

2. Provides a Private Endorsement Key (EK) to be used for PKI encryption

3. Provides Isolation Authentication and Validation functions run in a protected Trusted Execution Environment (TEE)

4. Provides a TPM 2.0-enabled device connection to a network to uniquely identity the endorsement key (EK) to prove its identity during the challenge-response sequence.

TPM 2.0 challenge-response Quiz (22 - 25 )

11.22 - What are the core TPM 2.0 Benefits for Software-Based Security (Pick One)?

1. Proof of device identity, Verification of device integrity, Tamper evidence

2. Prevent replay attacks, Bind keys to hardware and Secure remote authentication

3. Credential protection, Isolation: Authentication and Validation and Root of Trust

4. Hardware root of trust, Protection against physical attacks and Secure key management.

TPM 2.0 challenge-response Quiz (23 - 25 )

11.23 - How does TPM 2.0 Software-Based Security Isolate Authentication and Validation (Pick One)?

1. TPM-enabled entity system that uses cryptographic keys to generate a valid "response" based on the challenge from the Verifier to Isolate Authentication and Validation

2. When a TPM 2.0-enabled device attempts to connect to a network, it can use its unique endorsement key (EK) to prove its identity during the challenge-response sequence

3. Authentication and Validation functions run in a protected Trusted Execution Environment (TEE).

4. A verifier specifies a selection of Platform Configuration Registers (PCRs) whose values it wants to verify for Authentication and Validation Isolation.

TPM 2.0 challenge-response Quiz (24 - 25 )

11.24 - What is a TPM 2.0 Software-Based Security Trusted Execution Environment (TEE). (Pick Two)?

1. Used to execute a set of PCR values that are chosen to create an access policy.

2. Generates a nonce (a one-time, unpredictable number) ensures that an attacker cannot simply record a successful challenge-response and replay it later to gain unauthorized access.

3. TEE is a secure, isolated area within a device's main processor that protects code and data from the rest of the system, ensuring confidentiality and integrity.

4. Is a separate hardware chip, a software-based TEE "containerized" fTPM is accessed.

TPM 2.0 challenge-response Quiz (25 - 25 )

11.25 - What is Trusted Protected Module TPM 2.0 Challenge-Response Authentication (Choose all that Apply)?

1. Uses cryptographic methods to prove the identity of a user or system and authorize sensitive operations.

2. Uses protocols use a dynamic exchange to prevent replay attacks and secure key-based operations.

3. Supports challenge-response protocols through several mechanisms, primarily centered on its ability to perform cryptographic operations using keys and secrets that never leave the security of the TPM itself.

4. By providing a "response" computation within the TPM, it proves to a "challenger" that the system possesses the corresponding private key or secret.