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Kientha t1_iy3m2ka wrote

Reply to comment by Defleurville in eli5 How is computer memory deleted? by unlikemike123

And this is why flash storage devices are a nightmare for forensic purposes. With magnetic storage, you can attach a write blocker and know the data on the drive won't change so you can compare hash values and verify nothing changed. Flash memory however will randomly change data so you can't rely on hash values to prove nothing has changed

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Defleurville t1_iy3uvx0 wrote

Another precision for other readers, which I assume Kientha knows, is that when speaking of computers, “randomly” never means randomly, as computers are incapable of doing anything at random (even electronic slot machines aren’t random).

In some cases, in means “not in sequential order”: We don’t continue reading a dictionary from where we stopped last time, but we do go in looking for a specific word, not pop it open and read whatever’s on the page. In computer terms, despite not being at all random, this is called “random access”.

In other cases, it means “made to appear random to a human”. Computers can easily generate values where users can’t tell what it will pick next, but under identical circumstances (the “seed”) it will pick the same values in the same order every time. We generally “cheat” by incorporating the time (down to the millisecond) into generating the numbers, so it’s mostly unpredictable.

Changes in Flash data aren’t random, they’re 100% deterministic and predictable (knowing all the info): they’re just not readily predictable to a user, which is functionally basically the same.

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