Data Scrambling Purpose

Question

Can someone please explain to me what data scrambling is when it comes to a memory controller? According to Wikipedia, it somehow masks the user data with random patterns to prevent reverse engineering of a DRAM. But, it is also is used to finding electrical problems. Can someone please elaborate on these features of data scrambling? Thanks!

Answer 1

The Wikipedia article claimed:

Memory controllers integrated into certain Intel Core processors also provide memory scrambling as a feature that turns user data written to the main memory into pseudo-random patterns.[6][7] As such, memory scrambling prevents forensic and reverse-engineering analysis based on DRAM data remanence, by effectively rendering various types of cold boot attacks ineffective. However, this feature has been designed to address DRAM-related electrical problems, not to prevent security issues, so it may not be rigorously cryptographically secure.[8]

However, I think that this claim is somewhat misleading because it implies that the purpose of data scrambling is to prevent reverse engineering. In fact the cited sources (listed as [6][7] in the quote) say the following:

The memory controller incorporates a DDR3 Data Scrambling feature to minimize the impact of excessive di/dt on the platform DDR3 VRs due to successive 1s and 0s on the data bus. Past experience has demonstrated that traffic on the data bus is not random and can have energy concentrated at specific spectral harmonics creating high di/dt that is generally limited by data patterns that excite resonance between the package inductance and on-die capacitances. As a result, the memory controller uses a data scrambling feature to create pseudo-random patterns on the DDR3 data bus to reduce the impact of any excessive di/dt.

Basically the purpose of scrambling is to limit fluctuations in the current draw that is used on the DRAM data bus. There is nothing in the cited source to support the claim that it is designed to prevent reverse-engineering, though I suppose it is reasonable to assume that it might make reverse engineering more difficult. I'm not an expert in this area so I don't know for sure.

I have edited the Wikipedia article to remove the improperly sourced claim. Though I suppose someone could add it back it, but if so hopefully they can provide better sourcing.