[Cryptography] Photon beam splitters for "true" random number generation ?

Jerry Leichter leichter at lrw.com
Thu Dec 24 06:09:30 EST 2015

> patrick at laptop:~$ gpg --print-md sha256 scattered_leaves.jpg
> scattered_leaves.jpg:
> 171E2552 72B2FB96 94BBB675 9B3203A1
> ED799567 1A808711 25E54D12 B106DCDA
> # Then FWIW:
> patrick at laptop:~$ shred -u scattered_leaves.jpg
In the interest of paranoid completeness:  If your computer has an SSD rather than a traditional magnetic disk, shred won't actually destroy the data - its writes will simply go to new blocks on the SSD, and the old blocks will go onto an internal, inaccessible list for later cleaning and reuse.  Or perhaps it was detected as beginning to fail and got moved onto the internal bad block list, where no ordinary use of the device will ever touch it again.

In fact, short of physical destruction, there's no effective way to ensure that data written to an SSD is really gone.  (The latest version of MacOS recognizes this fact, and that almost all Macs sold today have only SSD's for storage, and its Disk Utility program no longer offers a "secure erase" function, as it has no way to implement it that actually *is* secure.)

Perhaps you should have run gpg directly on the file from the SD card your camera wrote it to (assuming that's how you transferred it) and them destroyed the SD card; they're pretty cheap after all.
                                                        -- Jerry

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