Homework5_Solution (1)

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Rutgers University *

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446

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Computer Science

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Jan 9, 2024

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Uploaded by dan47433

ECE 446/579:04 (Spring 2023) Homework #5 Solution 1. ( TCB and SGX ) As we discussed in the lecture, SGX is a security extension to the Intel processors that can significantly reduce the size of the trusted computing base (TCB) in the system. Please answer the following questions about TCB and SGX. (1) Why is it important to reduce the size of TCB? (2) What system components are in the TCB before and after SGX is applied? (1) TCB is the part of the system components that must be guaranteed secure to ensure a secure system. The smaller the TCB is, the easier to ensure its security and integrity. (2) Before: App, OS, VMM; After: a subpart of the app (OS and VMM are not in the TCB). 2. (Isolation) Hardware isolation is an important security feature provided by Intel SGX. Please describe how and why the code/data in the enclave is isolated from the rest of the system? (1) Data/code is encrypted (2) The Enclave Page Cache Map (EPCM) conducts security checks for enclave access. 3. (EPC and EPCM) What are the functionalities of enclave page cache (EPC) and enclave page cache map (EPCM)? Please describe how these two components work together to achieve a secure isolation of the enclave. EPC: contains enclave’s code and data. EPCM: conducts security checks for enclave access. EPCM contains an entry to point to each EPC page, which is used to perform check that ensures the untrusted OS is not maliciously behaving. (e.g., breaking the enclave boundary by having the same EPC pages to multiple enclaves.) 4. (Security of SGX) What kind of attacks in general could compromise SGX enclave? Please give one example of the attack and discuss the countermeasures. Side channel attacks (e.g., cache side channel attacks) and physical attacks (e.g., rowhammer attacks). We will discuss the details of these attacks and the countermeasures in Weeks 9 and 10). 5. (SGX vs. TrustZone) Intel SGX and ARM TrustZone are both hardware isolation techniques that can provide a secure execution environment for sensitive data and code in the application. (1) Please describe the similarities and differences between these two techniques. (2) What applications have benefited from SGX and TrustZone? Please give one example for each. (1) Similarities: both achieve a hardware isolated environment (secure world & enclave) to protect sensitive data and code. Differences: different way to implement the hardware isolation. TrustZone uses bus-level isolation, and SGX uses memory encryption. (2) SGX works on Intel platforms. For example, it can be used in cloud servers, which achieves hardware supported cloud containers. TrustZone works on ARM platforms for mobile applications. For example, we have discussed TrustZone based one time password (OTP) tokens, fTPM, and language runtime in the lecture.

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