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>Since the storage media in these IoT devices would not last long if true deletions were being performed constantly, “deleted” data is often simply invalidated

>Since the storage media in these IoT devices would not last long if true deletions were being performed constantly, “deleted” data is often simply invalidated and moved to an unused page in the block (in a process called “wear leveling”). These invalidated pages, which still contain the data, remain present until a block fills up with them and a true deletion is initiated. >Accessing flash memory that has been factory reset in this way does require some amount of technical skill and specialized equipment, but nothing that is a real barrier to the average enthusiast working at home. By that logic my iPhone 11, my Android phone, my Mac or my Windows PC doesn't wipe personal content either after factory reset Feels like a bit clickbait-ish But at least Macs have a built-in 7-pass erase option to comply with DOD standards https://techpatio.com/wp-content/uploads/2012/09/disk-utility-mac-osx.jpg https://techpatio.com/wp-content/uploads/2012/09/disk-utilit...

ashtonkem 5y ago
Do you have any sources for the assertion that resetting an iOS device doesn’t remove data?
- wrboyce 5y ago
  Do iOS devices not leverage full disk encryption? In which case I’d assume simply wiping the encryption keys/fde headers would be sufficient? (Which it almost certainly does.)
- croon 5y ago
  https://www.apple.com/ca/business-docs/iOS_Security_Guide.pdf https://www.apple.com/ca/business-docs/iOS_Security_Guide.pd... > The “Erase all content and settings” option in Settings obliterates all the keys in Effaceable Storage, rendering all user data on the device cryptographically inaccessible. Semantics debate around whether leaving data practically inaccessible is the same as removing it, but considering where we are, I'd say it isn't. Granted, this is from 2018, but I doubt the defaults and concept have changed.
  - Retric 5y ago
    Securely deleting the keys is safer than simply practically inaccessible. That suggests their is some impractical way to access the data, care to suggest what that might be?
    - emsy 5y ago
      Overwriting flash with 0s. To be fair I think the iPhone should grant you that option (MacOs does). But to suggesting that leaving an encrypted block of data on the device is on the same level as leaving unencrypted blocks of data lying around is foolish.
      - deleted 5y ago
        [deleted]
      - Retric 5y ago
        Overwriting flash data isn’t going to give you access to the data. It might in theory be more secure, but I would favor encryption at rest rather than simply overwriting plain text.
    - jfrunyon 5y ago
      Encryption can be (and in fact certainly will be, given enough time) broken.
      - Retric 5y ago
        It is possible in theory to recover some information from overwriting flash data with zeros, it’s also possible in theory for well designed modern encryption to be broken but neither of those are guaranteed at this point.
        jfrunyon 5y ago
        Essentially every encryption scheme in history has been broken. It's a bit silly to think that "well designed modern" makes it safe. The others were all well designed and modern at one time, too. The only scheme that's truly unbreakable is a one-time pad and that's... well... not really practically useable. Personally, that's not a risk that I would care about (especially in the context of an Echo Dot or even an iPhone), but deleting the keys will not be better than inaccessible forever.
- vlovich123 5y ago
  Even if you didn’t have the public docs explaining this, you could make an educated guess because resetting the iOS device takes the same amount of time regardless of how much data you put on it and that time is on the order of 10s of seconds. iPhones don’t have erase speeds of 12gigabit/s - I don’t think there’s any storage technology that could do that. Also remember that Apple takes seriously the concern about the data leaking because the OS decided* to blacklist a bad block. Once a block has gone bad you probably shouldn’t rely on attempts to erase it working out. * if I recall correctly iOS devices don’t use a traditional flash controller and Apple does that mapping themselves (it’s also largely why Apple devices have better flash performance than competitors)
  - ashtonkem 5y ago
    > you could make an educated guess because resetting the iOS device takes the same amount of time regardless of how much data you put on it This is incorrect. Secure deletion should cover the entire disk no matter how much data was used before, in order to deny an attacker any information or to guide their recovery efforts. I would absolutely expect a secure deletion process to take the exact same amount of time regardless of how much data is used. A better tell is the difference between the same model of phone with different storage sizes. A 512GB iPhone should take 2x as long to securely wipe compared to a 256GB one, assuming they’re actually overwriting the encrypted data with random noise. > iPhones don’t have erase speeds of 12gigabit/s It’s worth pointing out that a true secure delete is actually a write not a delete. But it’s true that your typical iPhone could not possibly overwrite its entire disk in 10s or so, although last time I did a reset it took much longer than that.
    - vlovich123 5y ago
      > This is incorrect. Secure deletion should cover the entire disk no matter how much data was used before, in order to deny an attacker any information or to guide their recovery efforts. I would absolutely expect a secure deletion process to take the exact same amount of time regardless of how much data is used. That's a fair point. Still, mobile devices typically employ FDE to avoid the need for scribbling over the entire flash (also improves the lifetime of the flash in that way). > It’s worth pointing out that a true secure delete is actually a write not a delete Flash storage doesn't work that way unless you're referring to something else. To write a block you have to erase it first (makes the block all 1s or all 0s depending on the chip). An update of a block is technically then a read/erase/modify/write (although flash translation layers will elide the first 3 steps by writing to a free block & marking the old one as GC'able). Writing random patterns into flash to my knowledge generally isn't needed anyway as it was with magnetic storage. The only purpose of writing in a secure erase scenario is to try to overwhelm the flash translation layer to force every block to be touched. > although last time I did a reset it took much longer than that. I haven't profiled it, but any slowness erasing an iOS device is probably because the flash storage backing the secure element is optimized for reads rather than writes. Additionally, it may be erasing various metadata/caches in the OS storage that aren't covered by the encryption key.
deleted 5y ago
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wongarsu 5y ago
Concerning Windows, the help page about the factory reset states "You'll be asked to choose whether you want to erase data quickly or thoroughly. If you choose to erase data quickly, some data might be recoverable using special software. If you choose to erase data thoroughly, this will take longer but it makes recovering data less likely." [1] Of course deleting data on an SSD is tricky due to wear-leveling, anything short of telling the drive to erase the entire disk with the secure erase command isn't guaranteed to work. 1: https://support.microsoft.com/en-us/windows/how-to-refresh-reset-or-restore-your-pc-51391d9a-eb0a-84a7-69e4-c2c1fbceb8dd https://support.microsoft.com/en-us/windows/how-to-refresh-r...
orev 5y ago
This is why FDE is mostly the default on all of the devices you mention. The secret keys are stored in the TPM or equivalent. Most SSDs for Mac/PC also have an OEM software option to trigger a secure wipe using special software from the vendor. The problem here is that the Echo is closed so those options aren’t available to you. However, this is also a problem on other custom devices like printers.
sp332 5y ago
There is a command you can send to the drive that will erase all data including from those extra bookkeeping areas. "ATA Secure Erase". The drive has to support it of course.
gojomo 5y ago
I believe iOS handles this by ensuring all flash-written data is encrypted with an on-device key. A 'wipe' then definitively erases that key - making further overwrites of the freed data unnecessary. If the crypto is strong, and the key never exfiltrated, then this may be even better than an explicit overwrite, which on some media (like magnetic drives) may still leave trace hints of the old data that advanced techniques could recover.
- lolthishuman 5y ago
  I’ve read opsec material that no matter how many passes you do it can still be read. Hard to know for sure unless you know the stack in and out like the back of your hand.
  - tailspin2019 5y ago
    That’s probably true but the GP is likely drawing the distinction that iOS tries to do an “unrecoverable” delete as best it can whereas presumably the Echo is not doing this (encrypting the data and then deleting the key as part of the reset).
  - vlovich123 5y ago
    A lot of that opsec material is very dated back from when density was lower and you had a spinning disk. Do you have any that’s evidence-based that such techniques are needed for flash storage? If anything the opsec concerns are different. There’s very little that would force the controller to actually perform erase of specific blocks (eg the flash could blacklist blocks due to errors). To my knowledge that’s the primary concern, not that the data is still somehow recoverable once erased (which used to be true but I’m not sure holds for modern storage).
  - nyolfen 5y ago
    this does not apply to cryptoshredding or any modern storage media. even a single pass on magnetic media renders data unrecoverable.
  - jcrawfordor 5y ago
ThePowerOfFuet 5y ago
>By that logic my iPhone 11, my Android phone, my Mac or my Windows PC doesn't wipe personal content either after factory reset Your iPhone 11 zeroizes the cryptographic key used for the user data partition. It doesn't have to wipe it per se, but rather it renders it eternally inaccessible; then it creates a new key and sets up a new filesystem right over top of the old one (which now just has random data in the unallocated space).
- jfrunyon 5y ago
  If you really think the encryption will never ("eternally") be broken, I have sad news for you: it will.
  - barsonme 5y ago
    If AES is broken before your iPhone is destroyed then you have bigger problems than somebody reading your data.
re 5y ago
> But at least Macs have a built-in 7-pass erase option to comply with DOD standards I recently learned that the "zero out data" options are not available in Disk Utility for SSDs. This probably fine if you were using full disk encryption, especially on modern T2-chip Macs that always encrypt the built-in storage even if you haven't enabled FileVault, but it was a little concerning when I was getting rid of an old failing Mac that had an aftermarket SSD installed without encryption enabled.
- jeffbee 5y ago
  Yes it's really annoying because they also aren't available in the UI for fusion drives. You have to go into the command line tools in recovery mode, break the fusion drive volume down into its constituent pieces, and wipe the HDD separately, then rebuilt the fusion drive manually.
aeturnum 5y ago
The clickbait-y part is that it is possible to retrieve a token from the previous user. Pretty normal as you say. The non-clickbait is that the previous token is still valid as far as Amazon is concerned. They absolutely should have a process for invalidating tokens.
SV_BubbleTime 5y ago
The flash on your iPhone is nicer than cheaper embedded devices / microcontrollers. I have no idea what Echos use, but I’ve seen modern ARM micros have a 50k flash life expectancy or less. It’s not impossible to have a flash memory without a user data eeprom that you could “burn out” (in reality make less reliable). I have no idea if it’s true in this case, but the straight comparison / jump to iPhone 11 might also be speculative.
userbinator 5y ago
Interesting note: modern high-density NAND flash ("TLC", "QLC") is so sensitive to the data patterns being written (writing zero bits causes more wear than writing 1 bits - the latter being the default non-written state of the medium) that controllers need to use a scrambling algorithm to statistically balance the number of 0 and 1 bits that are written. Earlier schemes were based on LFSRs or similar, but then I guess someone noticed that an encryption algorithm would also do a similar job, with the advantage of it being much harder to create pathological cases (look up "CD-ROM weak sector protection" for an interesting rabbithole related to that) and "self-encrypting drive" also be a good marketing point. On the other hand, it's a nightmare for data recovery, especially the "I didn't ever mean to encrypt this drive, what do you mean you can't recover it?" situation. There's some discussion of the older version of that scheme (not encryption-based) here: https://joshuawise.com/projects/ndfrecovery https://joshuawise.com/projects/ndfrecovery
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PhasmaFelis 5y ago
> By that logic my iPhone 11, my Android phone, my Mac or my Windows PC doesn't wipe personal content either after factory reset If those work the same way, then no, they don't. If lots of other devices have the same problem, that doesn't make it better!
barsonme 5y ago
Macs with SSDs don’t have the 7-pass option because (from the horse’s mouth) it’s only effective for HDDs.
- thebruce87m 5y ago
  If you could reliably read data after 6 passes then HDDs would be 6 times larger with the same hardware. There is the further belief that state sponsored actors would be able to read them, but this relies that state sponsored actors 1) have hardware capable and 2) would only go to those lengths to get the data.
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ekianjo 5y ago
> By that logic my iPhone 11 Don't worry about your physical iPhone, all of your data is mostly already saved for you remotely where it can never be wiped ever.

ashtonkem 5y ago

Do you have any sources for the assertion that resetting an iOS device doesn’t remove data?

wrboyce 5y ago
Do iOS devices not leverage full disk encryption? In which case I’d assume simply wiping the encryption keys/fde headers would be sufficient? (Which it almost certainly does.)
croon 5y ago
https://www.apple.com/ca/business-docs/iOS_Security_Guide.pdf https://www.apple.com/ca/business-docs/iOS_Security_Guide.pd... > The “Erase all content and settings” option in Settings obliterates all the keys in Effaceable Storage, rendering all user data on the device cryptographically inaccessible. Semantics debate around whether leaving data practically inaccessible is the same as removing it, but considering where we are, I'd say it isn't. Granted, this is from 2018, but I doubt the defaults and concept have changed.
- Retric 5y ago
  Securely deleting the keys is safer than simply practically inaccessible. That suggests their is some impractical way to access the data, care to suggest what that might be?
  - emsy 5y ago
    Overwriting flash with 0s. To be fair I think the iPhone should grant you that option (MacOs does). But to suggesting that leaving an encrypted block of data on the device is on the same level as leaving unencrypted blocks of data lying around is foolish.
    - deleted 5y ago
      [deleted]
    - Retric 5y ago
      Overwriting flash data isn’t going to give you access to the data. It might in theory be more secure, but I would favor encryption at rest rather than simply overwriting plain text.
  - jfrunyon 5y ago
    Encryption can be (and in fact certainly will be, given enough time) broken.
    - Retric 5y ago
      It is possible in theory to recover some information from overwriting flash data with zeros, it’s also possible in theory for well designed modern encryption to be broken but neither of those are guaranteed at this point.
      - jfrunyon 5y ago
        Essentially every encryption scheme in history has been broken. It's a bit silly to think that "well designed modern" makes it safe. The others were all well designed and modern at one time, too. The only scheme that's truly unbreakable is a one-time pad and that's... well... not really practically useable. Personally, that's not a risk that I would care about (especially in the context of an Echo Dot or even an iPhone), but deleting the keys will not be better than inaccessible forever.
vlovich123 5y ago
Even if you didn’t have the public docs explaining this, you could make an educated guess because resetting the iOS device takes the same amount of time regardless of how much data you put on it and that time is on the order of 10s of seconds. iPhones don’t have erase speeds of 12gigabit/s - I don’t think there’s any storage technology that could do that. Also remember that Apple takes seriously the concern about the data leaking because the OS decided* to blacklist a bad block. Once a block has gone bad you probably shouldn’t rely on attempts to erase it working out. * if I recall correctly iOS devices don’t use a traditional flash controller and Apple does that mapping themselves (it’s also largely why Apple devices have better flash performance than competitors)
- ashtonkem 5y ago
  > you could make an educated guess because resetting the iOS device takes the same amount of time regardless of how much data you put on it This is incorrect. Secure deletion should cover the entire disk no matter how much data was used before, in order to deny an attacker any information or to guide their recovery efforts. I would absolutely expect a secure deletion process to take the exact same amount of time regardless of how much data is used. A better tell is the difference between the same model of phone with different storage sizes. A 512GB iPhone should take 2x as long to securely wipe compared to a 256GB one, assuming they’re actually overwriting the encrypted data with random noise. > iPhones don’t have erase speeds of 12gigabit/s It’s worth pointing out that a true secure delete is actually a write not a delete. But it’s true that your typical iPhone could not possibly overwrite its entire disk in 10s or so, although last time I did a reset it took much longer than that.
  - vlovich123 5y ago
    > This is incorrect. Secure deletion should cover the entire disk no matter how much data was used before, in order to deny an attacker any information or to guide their recovery efforts. I would absolutely expect a secure deletion process to take the exact same amount of time regardless of how much data is used. That's a fair point. Still, mobile devices typically employ FDE to avoid the need for scribbling over the entire flash (also improves the lifetime of the flash in that way). > It’s worth pointing out that a true secure delete is actually a write not a delete Flash storage doesn't work that way unless you're referring to something else. To write a block you have to erase it first (makes the block all 1s or all 0s depending on the chip). An update of a block is technically then a read/erase/modify/write (although flash translation layers will elide the first 3 steps by writing to a free block & marking the old one as GC'able). Writing random patterns into flash to my knowledge generally isn't needed anyway as it was with magnetic storage. The only purpose of writing in a secure erase scenario is to try to overwhelm the flash translation layer to force every block to be touched. > although last time I did a reset it took much longer than that. I haven't profiled it, but any slowness erasing an iOS device is probably because the flash storage backing the secure element is optimized for reads rather than writes. Additionally, it may be erasing various metadata/caches in the OS storage that aren't covered by the encryption key.

deleted 5y ago

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wongarsu 5y ago

Concerning Windows, the help page about the factory reset states "You'll be asked to choose whether you want to erase data quickly or thoroughly. If you choose to erase data quickly, some data might be recoverable using special software. If you choose to erase data thoroughly, this will take longer but it makes recovering data less likely." [1] Of course deleting data on an SSD is tricky due to wear-leveling, anything short of telling the drive to erase the entire disk with the secure erase command isn't guaranteed to work. 1: https://support.microsoft.com/en-us/windows/how-to-refresh-reset-or-restore-your-pc-51391d9a-eb0a-84a7-69e4-c2c1fbceb8dd https://support.microsoft.com/en-us/windows/how-to-refresh-r...

orev 5y ago

This is why FDE is mostly the default on all of the devices you mention. The secret keys are stored in the TPM or equivalent. Most SSDs for Mac/PC also have an OEM software option to trigger a secure wipe using special software from the vendor. The problem here is that the Echo is closed so those options aren’t available to you. However, this is also a problem on other custom devices like printers.

sp332 5y ago

There is a command you can send to the drive that will erase all data including from those extra bookkeeping areas. "ATA Secure Erase". The drive has to support it of course.

gojomo 5y ago

I believe iOS handles this by ensuring all flash-written data is encrypted with an on-device key. A 'wipe' then definitively erases that key - making further overwrites of the freed data unnecessary. If the crypto is strong, and the key never exfiltrated, then this may be even better than an explicit overwrite, which on some media (like magnetic drives) may still leave trace hints of the old data that advanced techniques could recover.

lolthishuman 5y ago
I’ve read opsec material that no matter how many passes you do it can still be read. Hard to know for sure unless you know the stack in and out like the back of your hand.
- tailspin2019 5y ago
  That’s probably true but the GP is likely drawing the distinction that iOS tries to do an “unrecoverable” delete as best it can whereas presumably the Echo is not doing this (encrypting the data and then deleting the key as part of the reset).
- vlovich123 5y ago
  A lot of that opsec material is very dated back from when density was lower and you had a spinning disk. Do you have any that’s evidence-based that such techniques are needed for flash storage? If anything the opsec concerns are different. There’s very little that would force the controller to actually perform erase of specific blocks (eg the flash could blacklist blocks due to errors). To my knowledge that’s the primary concern, not that the data is still somehow recoverable once erased (which used to be true but I’m not sure holds for modern storage).
- nyolfen 5y ago
  this does not apply to cryptoshredding or any modern storage media. even a single pass on magnetic media renders data unrecoverable.
- jcrawfordor 5y ago

ThePowerOfFuet 5y ago

>By that logic my iPhone 11, my Android phone, my Mac or my Windows PC doesn't wipe personal content either after factory reset Your iPhone 11 zeroizes the cryptographic key used for the user data partition. It doesn't have to wipe it per se, but rather it renders it eternally inaccessible; then it creates a new key and sets up a new filesystem right over top of the old one (which now just has random data in the unallocated space).

jfrunyon 5y ago
If you really think the encryption will never ("eternally") be broken, I have sad news for you: it will.
- barsonme 5y ago
  If AES is broken before your iPhone is destroyed then you have bigger problems than somebody reading your data.

re 5y ago

> But at least Macs have a built-in 7-pass erase option to comply with DOD standards I recently learned that the "zero out data" options are not available in Disk Utility for SSDs. This probably fine if you were using full disk encryption, especially on modern T2-chip Macs that always encrypt the built-in storage even if you haven't enabled FileVault, but it was a little concerning when I was getting rid of an old failing Mac that had an aftermarket SSD installed without encryption enabled.

jeffbee 5y ago
Yes it's really annoying because they also aren't available in the UI for fusion drives. You have to go into the command line tools in recovery mode, break the fusion drive volume down into its constituent pieces, and wipe the HDD separately, then rebuilt the fusion drive manually.

aeturnum 5y ago

The clickbait-y part is that it is possible to retrieve a token from the previous user. Pretty normal as you say. The non-clickbait is that the previous token is still valid as far as Amazon is concerned. They absolutely should have a process for invalidating tokens.

SV_BubbleTime 5y ago

The flash on your iPhone is nicer than cheaper embedded devices / microcontrollers. I have no idea what Echos use, but I’ve seen modern ARM micros have a 50k flash life expectancy or less. It’s not impossible to have a flash memory without a user data eeprom that you could “burn out” (in reality make less reliable). I have no idea if it’s true in this case, but the straight comparison / jump to iPhone 11 might also be speculative.

userbinator 5y ago

Interesting note: modern high-density NAND flash ("TLC", "QLC") is so sensitive to the data patterns being written (writing zero bits causes more wear than writing 1 bits - the latter being the default non-written state of the medium) that controllers need to use a scrambling algorithm to statistically balance the number of 0 and 1 bits that are written. Earlier schemes were based on LFSRs or similar, but then I guess someone noticed that an encryption algorithm would also do a similar job, with the advantage of it being much harder to create pathological cases (look up "CD-ROM weak sector protection" for an interesting rabbithole related to that) and "self-encrypting drive" also be a good marketing point. On the other hand, it's a nightmare for data recovery, especially the "I didn't ever mean to encrypt this drive, what do you mean you can't recover it?" situation. There's some discussion of the older version of that scheme (not encryption-based) here: https://joshuawise.com/projects/ndfrecovery https://joshuawise.com/projects/ndfrecovery

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PhasmaFelis 5y ago

> By that logic my iPhone 11, my Android phone, my Mac or my Windows PC doesn't wipe personal content either after factory reset If those work the same way, then no, they don't. If lots of other devices have the same problem, that doesn't make it better!

barsonme 5y ago

Macs with SSDs don’t have the 7-pass option because (from the horse’s mouth) it’s only effective for HDDs.

thebruce87m 5y ago
If you could reliably read data after 6 passes then HDDs would be 6 times larger with the same hardware. There is the further belief that state sponsored actors would be able to read them, but this relies that state sponsored actors 1) have hardware capable and 2) would only go to those lengths to get the data.

deleted 5y ago

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ekianjo 5y ago

> By that logic my iPhone 11 Don't worry about your physical iPhone, all of your data is mostly already saved for you remotely where it can never be wiped ever.