It's a legitimate concern given the potential, but perhaps not a realistic concern.
Consider though, the data is digital, and error corrected, but it is written onto a fundamentally analog medium. By reading the medium you can easily determine the last written data which then lets you determine to a rather high precision the signal that was used to write that data (because it's all digital). That then allows you to subtract that signal from your analysis without leaving a ton of residual noise. Now perhaps there isn't much left after that, but what is left will be designed to be read even in the midst of noise, because it employs error correction. Who knows what the theoretical limit of such detection is with state of the art technology.
The evidence does tend to argue against any similar techniques of data recovery being used in practice anywhere today. Does that mean you should feel safe?
Much of Feenberg's argument here rests on technology. STM, MFM scanning. Image storage and processing. Tens of terabytes of data would need to be captured and processed, etc. Technology is not static though. What is the likelihood that there will be significant advances in STM/MFM scanning in the near future? In image storage and processing? In storage capacities in the ten terabyte range? For all of these it's a near certainty that we will continue to see exponential advances for the foreseeable future.
So perhaps abandoning your hard-drive that has been "wiped" once to the vagaries of the world is a safe bet today. But what happens in 10, 20, 30 years when all of those technologies have advanced remarkably and it is not only possible but perhaps even trivial to recover data on such drives? That is the conundrum.
Generally speaking, if you think your drives have contained material which you do very much wish to remain confidential in perpetuity, it probably makes sense to destroy old hard-drives rather than re-sell them. Though the cost/benefit trade-off may be a bit different if you are a business with a lot of data.
SSDs store data by tunneling charges onto and off of floating gates. I strongly suspect that a TLA entity can recover data from the residual charges just as readily as they can from residual magnetism on a spinning media drive.
Having said that, like many others in this discussion, I'm skeptical of how practical data recovery really is vs. a theoretical issue. I'm guessing that the value of the data has to be extremely high before it would be worth while going to the necessary lengths.
Consider though, the data is digital, and error corrected, but it is written onto a fundamentally analog medium. By reading the medium you can easily determine the last written data which then lets you determine to a rather high precision the signal that was used to write that data (because it's all digital). That then allows you to subtract that signal from your analysis without leaving a ton of residual noise. Now perhaps there isn't much left after that, but what is left will be designed to be read even in the midst of noise, because it employs error correction. Who knows what the theoretical limit of such detection is with state of the art technology.
The evidence does tend to argue against any similar techniques of data recovery being used in practice anywhere today. Does that mean you should feel safe?
Much of Feenberg's argument here rests on technology. STM, MFM scanning. Image storage and processing. Tens of terabytes of data would need to be captured and processed, etc. Technology is not static though. What is the likelihood that there will be significant advances in STM/MFM scanning in the near future? In image storage and processing? In storage capacities in the ten terabyte range? For all of these it's a near certainty that we will continue to see exponential advances for the foreseeable future.
So perhaps abandoning your hard-drive that has been "wiped" once to the vagaries of the world is a safe bet today. But what happens in 10, 20, 30 years when all of those technologies have advanced remarkably and it is not only possible but perhaps even trivial to recover data on such drives? That is the conundrum.
Generally speaking, if you think your drives have contained material which you do very much wish to remain confidential in perpetuity, it probably makes sense to destroy old hard-drives rather than re-sell them. Though the cost/benefit trade-off may be a bit different if you are a business with a lot of data.