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I'd like to ask a question. Does filling phone memory with junk data actually overwrite all previous data. Just in case I would like to say that I'm asking for android and iphone memory. And is eeprom used in these phone or flash memory?

ps i also would like to ask one more thing. in iphone(above 3gs) when you factory reset the data in encrypted and the keys are deleted. so is the data in the worn out area also encrypted

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  • EEPROM would be only used for firmware storage, if at all these days. You will (hopefully) never be able to overwrite that with just filling the user's memory.
    – Marcel
    Nov 1, 2016 at 11:34
  • as long as you fill it up all the way, and repeat a few times to rotate the reserved slack, over-write data is almost impossible to recover. I like to keep full flash drives for that purpose: download the secret then refill with small MP3s until full, delete some, refill, safe.
    – dandavis
    Nov 1, 2016 at 19:09
  • If you keep on filling and erasing data, that deleted data becomes so tampered such that you won't be able to recover or read that data again. The only way scientists have figured out to recover worst condition data is by using electron microscope.
    – defalt
    Nov 3, 2016 at 12:02
  • are you sure that if we keep filling and removing data it becomes unrecoverable
    – user119003
    Nov 5, 2016 at 9:49

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No, not necessarily. Flash memory uses wear levelling (changing the physical location of data stored) to maximize memory life. Most flash memory has some "spare" space that is unreported that allows it to replace bad parts as they wear out. This means that there may well be small amounts of (worn/bad) memory that still holds some of your data even after overwriting all memory reported by the phone. However the data on this memory would be arbitrary and I would expect it would require forensic tools to recover it.

I'm not sure on the eeprom/flash part

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  • i also would like to ask one more thing. in iphone(above 3gs) when you factory reset the data in encrypted and the keys are deleted. so is the data in the worn out area also encrypted
    – user119003
    Nov 3, 2016 at 9:46
  • and do these file shredders also overwrite the worn out data
    – user119003
    Nov 3, 2016 at 10:13
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    As Marcel reported above, eeprom is used for small memory storage such as firmware, rather than for user data. Among other things eeprom is more expensive than flash memory, so manufacturers make less profit if they use a lot of it. To prevent the problem of data leakage due to wear leveling in flash drives, encrypt the drive when you first start using it. The worn sectors may still be recoverable with forensic tools, but the data remains encrypted. The only secure method of wiping non-encrypted data on flash memory is with a large hammer (physical destruction). Nov 4, 2016 at 10:34
  • @MarkRipley Flash memory is actually eeprom but with different architecture from that eeprom which is used in PC. Both are made up of Nand flash.
    – defalt
    Nov 4, 2016 at 13:18
  • @MarkRipley and what if the data is unencrypted
    – user119003
    Nov 5, 2016 at 9:52

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