Write short notes on Software Fault Isolation (SFI)i. Goal and solution, ii. SFI approach.

Software Fault Isolation (SFI) in a Nutshell:

Goal and Solution:

1. Problem: Unsafe languages like C lack built-in memory safety, making programs susceptible to runtime errors and security vulnerabilities.
2. Solution: SFI provides a runtime safeguard by transforming programs, especially those from untrusted sources, to confine their memory access within a secure area, or “sandbox.”

SFI Approach:

Transformation at Binary Level: SFI transforms the program at the binary level by adding code sequences to enforce memory boundaries.

Post-transformation Verification: After transformation, a trusted SFI verifier ensures the code’s compliance with safety constraints.

Simplicity for Verification: Since the verifier assumes the code has undergone SFI, it remains simple, reducing both verification time and the Trusted Computing Base.

Proof Carrying Code Concept: This is akin to Proof Carrying Code, where an untrusted compiler generates code, and a trusted or verified binary verifier ensures adherence to safety measures.

Suitability for Untrusted Code: Traditional SFI is particularly effective for executing binary code from untrusted sources, adding a layer of security to potentially risky software.