Secure communications between peers using a verified virtual trusted platform module

• US 10,592,678 B1
• Filed: 09/09/2016
• Issued: 03/17/2020
• Est. Priority Date: 09/09/2016
• Status: Active Grant

• Current Assignee: Musarubra US LLC (Musarubra US SellCo LLC)
• Original Assignee: FireEye, Inc. (Alphabet Inc.)
• Inventors: Ismael, Osman Abdoul, Tews, Hendrik
• Primary Examiner(s): Lagor, Alexander
• Assistant Examiner(s): Tran, Wu V
• Application Number:
  US15/261,104
• Time in Patent Office: 1,285 Days
• CPC Class Codes: G06F 11/3692 for test results analysis
• CPC Class Codes: G06F 21/53 by executing in a restricted environment, e.g. sandbox or secure virtual machine
• CPC Class Codes: G06F 21/62 Protecting access to data via a platform, e.g. using keys or access control rules
• CPC Class Codes: H04L 2209/127 Trusted platform modules [TPM]
• CPC Class Codes: H04L 2209/26 Testing cryptographic entity, e.g. testing integrity of encryption key or encryption algorithm
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords
• CPC Class Codes: H04L 9/0897 involving additional devices, e.g. trusted platform module [TPM], smartcard or USB

Abstract

The embodiments herein are directed to a technique for providing secure communication between nodes of a network environment or within a node of the network using a verified virtual trusted platform module (TPM) of each node. The verified virtual TPM illustratively emulates a hardware TPM device to provide software key management of cryptographic keys used to provide the secure communication over a computer network of the network environment. Illustratively, the verified virtual TPM is configured to enforce a security policy of a trusted code base (TCB) that includes the virtual TPM. Trustedness denotes a predetermined level of confidence that the security property is demonstrated by the verified virtual TPM. The predetermined level of confidence is based on an assurance (i.e., grounds) that the verified virtual TPM demonstrates the security property. Trustedness of the virtual TPM may be verified by subjecting the virtual TPM to enhanced verification analysis configured to ensure conformance to an operational model with an appropriate level of confidence over an appropriate range of activity. The operational model may then be configured to analyze conformance to the security property. A combination of conformance by the virtual TPM to the operational model and to the security property provides assurance (i.e., grounds) for the level of confidence and, thus, verifies trustedness.

Claims

1. A method for establishing secure communications over a network in accordance with verifiable secure software key management, comprising:

verifying a virtual trusted platform module (TPM) being software that emulates operations of a hardware TPM, the virtual TPM is configured to manifest a security property that enforces a security policy preventing alteration of content within a secure memory by software external to the virtual TPM, wherein the security property is manifested by subjecting code including at least a first portion of the virtual TPM to enhanced verification analyses to confirm that (i) the code conforms to an operational model including key elements of the code and (ii) the virtual TPM demonstrates the security property; and

providing the virtual TPM for deployment within a node, wherein the virtual TPM being configured to generate one or more cryptographic keys on the node, store the one or more cryptographic keys within the secure memory, and safeguard content of the secure memory including the one or more cryptographic keys for use in establishing secure communications over the network.

2. The method of claim 1 wherein the virtual TPM demo security policy provides for the virtual TPM to be immutable.

3. The method of claim 1 wherein the virtual TPM demonstrates the security property by at least verifying that at least a predetermined level of confidence exists based on a comparison of at least states associated with at least the first portion of the virtual TPM to states produced by the operational model.

4. The method of claim 3 wherein the comparison of at least the states associated with at least the first portion of the virtual TPM to the states produced by the operational model comprises:

generating an executable of the operational model;

initiating a state dump of the operational model;

initiating a corresponding state dump of the first portion of the virtual TPM;

iteratively comparing the states of the executable operational model and the first portion of the virtual TPM; and

continuing iterative comparison of the states of the executable operational model and the first portion of the virtual TPM until a predetermined number of states match, wherein the predetermined number of matched states form a sufficient test coverage between the executable operational model and the first portion of the virtual TPM.

5. The method of claim 1 wherein the virtual TPM includes the first portion being a verified subset of a fully compliant TPM interface and a second portion implementing a remaining subset of the fully compliant TPM interface, and wherein the second portion is not verified for the security property.

6. The method of claim 1 wherein the security property is verified by proving the security property on a theorem prover.

7. The method of claim 1 wherein the code includes a trusted code base and the virtual TPM corresponds to a software module of the trusted code base.

8. The method claim 1 wherein the code conforms to the operational model with an appropriate level of confidence over an appropriate range of activities including inputs, outputs and operational states.

9. The method of claim 1 wherein storing the cryptographic key in the secure memory comprises protecting the cryptographic key stored in the secure memory with a password provided by a peer.

10. The method of claim 7 wherein a combination of conformance by the virtual TPM to the operational model and to the security property provides assurances for a level of confidence that verifies trustedness to yield the virtual TPM.

11. The method of claim 10 wherein the trustedness of the virtual TPM is set by demonstrating that an instruction issued by a module external to the code and having one or more arguments configured to alter an expected behavior or state of the virtual TPM related to the security property results in a violation in which the instruction is rejected or ignored and prevented from execution.

12. The method of claim 1 wherein the virtual TPM includes the first portion being a verified subset of the code functioning to verify access to the secure memory and a second portion being software module, separate from the code and non- verified, for handling encrypting of data for the virtual TPM.

14. The system of claim 12 wherein the virtual TPM operates as a verifiable secure software key management system for controlling access one or more cryptographic keys stored within the secure memory.

15. The system of claim 12 wherein virtual TPM enables secure communication between a node including the virtual TPM and a TPM of a second node, different than the node, over a network environment.

16. The system of claim 15 wherein the security property is verified with a predetermined level of confidence based on a comparison of at least states of a trusted portion of the virtual TPM to states produced by an operational model and the comparison of at least states of the trusted portion of the virtual TPM to states produced by the operational model is conducted to verify the security property by at least:

generating an executable of the operational model;

initiating a state dump of the operational model;

initiating a corresponding state dump of the trusted portion of the virtual TPM;

iteratively comparing the states of the executable operational model and the trusted portion of the virtual TPM; and

continuing iterative comparison of the states of the executable operational model and the trusted portion of the virtual TPM until a predetermined number of states match, wherein the predetermined number of matched states form a sufficient test coverage between the executable operational model and the trusted portion of the virtual TPM.

18. The system of claim 15 wherein the virtual TPM is deployed within a node operating in the network.

19. The system of claim 15 wherein the security property is verified by proving the security property on a theorem prover.

20. The system of claim 16 wherein the executable operational model initiates on-demand the state dump of the operational model and the corresponding state dump of the trusted portion of the virtual TPM.

21. The system of claim 15 wherein the cryptographic key included in the secure memory is protected with a password provided by a peer having access to the second node.

13. A system comprising:

a central processing unit (CPU) adapted to execute a verified virtual trusted platform module (TPM) being software that emulates operations of a hardware TPM;

a memory configured to store code operating as a trusted computing base (TCB), and the virtual TPM being a part of the TCB; and

a secure memory configured from a portion of the memory by the TCB, wherein

the virtual TPM having been configured to manifest a security property that enforces a security policy preventing alteration of content within the secure memory by software external to the virtual TPM, the security property is manifested by subjecting at least a first portion of the virtual TPM to enhanced verification analyses to confirm that (i) the code conforms to an operational model including key elements of the TCB and (ii) the virtual TPM demonstrates the security property.

17. The system of claim 13 wherein the virtual TPM includes the first portion being a first subset of code representing the virtual TPM with the security property verified with a predetermined level of confidence based on state comparisons between the first portion of the virtual TPM and an operational model and a second portion implementing a remaining subset of the code representing the virtual TPM.

22. A non-transitory computer readable medium including program instructions for execution on a processor of a node on a network, the program instructions when executed operable to:

generate at least a cryptographic key using a verified virtual trusted platform module (TPM) being a portion of code that emulates a hardware TPM, wherein the virtual TPM manifesting a security property that enforces a security policy to prevent alteration of a state related to security of the virtual TPM by software external to the virtual TPM, wherein the security property is verified to a predetermined level of confidence based on a state comparison of at least states of a first portion of the virtual TPM to states produced by an operational model including key elements of the code and the virtual TPM safeguards contents of a secure memory accessible by the virtual TPM;

store the cryptographic key in the secure memory; and

communicate securely over the network with a peer using the cryptographic key.

23. The non-transitory computer readable medium of claim 22 wherein the security policy provides for the virtual TPM to be immutable.

24. The non-transitory computer readable medium of claim 22 wherein the virtual TPM demonstrates the security property by at least verifying that at least states associated with at least a predetermined level of confidence exists based on a comparison of at least states associated with at least the first portion of the virtual TPM to states produced by the operational model.

25. The non-transitory computer readable medium of claim 24 wherein the comparison of at least the states associated with at least the first portion of the virtual TPM to the states produced by the operational model comprises:

generating an executable of the operational model;

initiating a state dump of the operational model;

initiating a corresponding state dump of the first portion of the virtual TPM;

iteratively comparing the states of the executable operational model and the first portion of the virtual TPM; and

continuing iterative comparison of the states of the executable operational model and the first portion of the virtual TPM until a predetermined number of states match, wherein the predetermined number of matched states form a sufficient test coverage between the executable operational model and the first portion of the virtual TPM.

26. The non-transitory computer readable medium of claim 22 wherein the virtual TPM includes the first portion being a verified subset of a fully compliant TPM interface and a second portion implementing a remaining subset of the fully compliant TPM interface, and wherein the second portion is not verified for the security property.

27. The non-transitory computer readable medium of claim 22 wherein the security property is verified by proving the security property on a theorem prover.

28. The non-transitory computer readable medium of claim 22 wherein the code includes a trusted code base and the virtual TPM corresponds to a software module of the trusted code base.

29. The non-transitory computer readable medium of claim 22 wherein the code conforms to the operational model with an appropriate level of confidence over an appropriate range of activities including inputs, outputs and operation states.

30. The non-transitory computer readable medium of claim 22 wherein storing the cryptographic key in the secure memory comprises protecting the cryptographic key stored in the secure memory with a password provided by a peer.

31. The non-transitory computer readable medium of claim 29 wherein a combination of conformance by the TPM to the operational model and to the security property provides assurances for a level of confidence that verifies trustedness to yield the virtual TPM.