What is really slowing down your withdrawals? (Hint: they are not your tools)

In digital forensics we invest in cutting-edge tools… and then we connect everything with the first cable we find in a drawer.

Bad idea.

During our testing, the difference between using different cables with the same device meant completing an extraction in minutes… or losing hours. The key is what is actually inside the cable. If your extractions are slow, inconsistent, or eternally long, this could be the reason.

In a digital forensics lab we tend to obsess over the choice of processor, the brand of write blockers, and software licenses that cost more than a small car (or even a house, in some cases). However, we connect all of this using a £3 cable taken from a drawer and then wonder why the extraction takes so long that it gives us time to finish a novel.

The cable matters a lot more than it should. And not because of the bandwidth that appears printed on the coating, but because of the engineering inside, which is usually much worse than we imagine.

The numbers

A modern 128 GB Android phone. The same workstation. The same software. Four different cables.

Between the worst and best results, more than 70 minutes were saved on a physical extraction and potentially more than two hours on a Full File System (FFS) extraction.

When working through an evidence queue, that doesn't equate to a coffee or lunch break. That's half a day wasted on a single device.

If you're wondering why FFS extracts are typically slower than physical extracts, even when they extract less data, the answer is simple: an FFS extract is not a single sequential read. It involves hundreds of thousands of operations on small files, each with its own protocol overhead and, when the wire is poor, multiple opportunities for silent retries.

Bad cables don't make up for their shortcomings over a continuous transfer. Your problems multiply at every file boundary, every database, every cached thumbnail, and every conversation attachment.

Bandwidth is not the answer

The most obvious conclusion would be to think that faster cables took advantage of their greater bandwidth capacity. I wish it were that simple.

Most smartphones today are limited to USB 3.2 Gen 1 (5 Gbps) or USB 3.2 Gen 2 (10 Gbps), and none offer Thunderbolt or USB4 v2.0 connections.

Your phone has no idea what PAM-3 ternary signaling is and, frankly, it doesn't care either.

The two best cables in this test operated at exactly the same negotiated link speed. The performance difference occurred within the same 5 Gbps connection.

In both cases, the bandwidth advertised on the outside of the cable was simply decorative.

La certificación es la verdadera señal

Ambos cables con mejor rendimiento superaron las pruebas USB4 realizadas mediante un lector de eMarker. Sin embargo, solo uno de ellos aprobó las pruebas de certificación Thunderbolt.

The 40Gbps cable failed Thunderbolt 3, Thunderbolt 4, and Thunderbolt 5 certifications in every case—a whole series of red crosses that looked like the report card of a student in serious trouble.

Thunderbolt certification is considerably more demanding than USB4 certification. It requires tighter shielding, better impedance matching, lower insertion losses, and an eMarker chip that doesn't "overdo" its capabilities.

A cable that fails Thunderbolt testing can still advertise 40Gbps speeds in its eMarker, just as a small fast food joint can claim to be “world famous.”

When connection quality is poor, the host and device spend a significant portion of time silently retrying the transmission of corrupted packets. The negotiated speed remains the same, but the effective throughput plummets.

In a physical extraction, that's where a good part of the morning is wasted. In a Full File System (FFS) extraction, that is where practically the entire day disappears.

Practical recommendations

Check cables before use

Use an eMarker reader to check cables before adding them to your lab.

Cables can be misleading: the information printed on the case may say one thing, while the internal electronics tell a completely different story.

Additionally, cables degrade with use, so it is a good idea to re-evaluate them periodically.

Consider Thunderbolt certification as an indicator of quality

No smartphone I review will negotiate a Thunderbolt connection during a forensic extraction.

Certification is not important because of the standard itself, but because of the level of engineering necessary to obtain it.

Buy based on certification, not bandwidth

The labels “Thunderbolt 4” (TBT4) or “Thunderbolt 5” (TBT5) imply formal validation by Intel.

In contrast, a box that promises “80 Gbps” simply reflects what the manufacturer decided to print on the packaging.

Avoid bottlenecks in the rest of the chain

Use rear USB ports directly connected to the workstation's motherboard, NVMe drives as acquisition targets, and, where possible, additional ventilation to prevent the phone from reducing its performance due to temperature.

A great cable connected to a low-quality USB-A adapter is still a bottleneck.

Conclusion

The bandwidth of a cable is a marketing data.

The certification of a cable is an engineering data.

The difference between the two, on a real device undergoing forensic analysis, can represent more than an hour for a physical extraction and much of an afternoon for a full file system extraction.

If you have a cable tester, use it.

And if a cable doesn't pass Thunderbolt certification tests, it will probably still work. It'll just take long enough for you to remember exactly which cable you used... and end up developing a bit of a dislike for it.

Avoid that problem.

Buy a quality cable.

Your evidence queue will thank you.