> I'd speculate that you need at least one of the compilers to be trusted otherwise they could both be subverted to produce X, Y that would produce matching V,

> I'd speculate that you need at least one of the compilers to be trusted otherwise they could both be subverted to produce X, Y that would produce matching V, W binaries with the attack still in place on both. Ideally one of them is not compromised. But if both are compromised but by different backdoors, the resulting binary will not be bit-for-bit identical (as they include different backdoors). So you can still detect it, and that's really all DDC can do. The only way to get a bit-for-bit identical binary from two compromised compilers is if they both have the same backdoor.