Paperkey 1.3

Johan Wevers johanw at
Sat Jan 5 13:55:26 CET 2013

On 04-01-2013 20:30, David Shaw wrote:

> That's a very good point.  Do you know of any studies on the projected life of flash
> when used as backup?

That depends strongly on the type of flash. NOR-flash, which is not used
any more in new devices gave problems after not many rewrites. NAND
flash is much more durable.

However, when you buy a new device and use it for long term backup
purposes (no/very few rewrites) AFAIK it can last very long. The main
thing that could damage it when it's just stored is radioactive
radiation like cosmic rays.

Personally I'm a heavy user of USB flash, also for backups, and the only
problems I ever had were software related (e.g. a 64-bit windows 7
computer that had the tendency to corrupt Truecrypt images). Of cource
this is anecdotical and I seem to be lucky about it; my oldest CD-ROM
backups from 1998 are also still readable.

> The few numbers I've seen at manufacturers websites about retention specifically,
> suggest it's around 10 years (depending on how well the flash is
stored - heat
> makes it die quicker, etc).

My oldest flash drive is still readable but it's not 10 years old yet.
But I am keeping it and will test it every now and then.

ir. J.C.A. Wevers
PGP/GPG public keys at

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