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I've always heard from smartphone experts that files aren't always 100% wiped off memory cards, ssd, hdd or other form of memories, if my phone gets stolen for example and I have used my phone to store sensitive information like in PDF format or TXT files that consist of recovery seeds can someone get their hands on these files if the phone was formatted before getting stolen?

Yes, possible that they can recover files from the phone even if it is totally formatted. There is a tool called JTAG that mostly use for repairing phones and also use to recover files the process is a bit dangerous if you don't have knowledge of using JTAG it's direct to nand/memory IC and then can dump/recover your files instantly.

If you want to delete or erase them totally before you format your phone you need some apps called data eraser or shreddit to permanently delete files and then those files are irrecoverable. Now, you are safe to reformat your phone without worrying about sensitive files that you don't want to expose.

Not right to store seed phrase and the likes on phone. Get a paper, write it down and have like two or three backups in different locations.

I remember when I deleted a phone audio recording on my Android phone, I used an app (but I do not remember the exact one) to recover many videos, audios, photos and files that I had deleted long time ago. Those files can still be recovered until certain period of time, but not when you formatted (hard reset) your phone.

Although, I couldn't get hold of the call recording I was looking for, but there were a lot that were recovered which I had deleted long time ago.

Formatting or performing a factory reset is not a reliable way of permanently deleting data. Both of these things simply delete the pointers to your the data, telling your phone or other device that these sectors are now free to be used for other purposes. But unless you actually write something else to these sectors, the data on them is not deleted and can be recovered, even after a hard reset. This is the basis behind the specialized apps that BitMaxz mentions above - to actually overwrite all your sensitive data in these sectors with junk data, meaning it cannot be recovered.

Why would you ever do this? Seed phrases should be stored offline using pen and paper. If you must store them electronically, then they should be stored encrypted on airgapped devices. Storing them in plain text on a phone is a recipe for disaster, even worse if your phone then automatically backs them up to the cloud or similar.

Not only is it completely unreasonable to use smartphones as a storage for some sensitive information and then be afraid that we will lose the device or someone will steal it - but it should be taken into account that at some point that device will very likely end up in the trash or we will sell it, and then someone will try to extract everything that is in the storage of such devices.

That's why I personally never throw away old phones, memory cards or hard drives - because it's not something that takes up a lot of space. In case you really want to destroy them, take out the battery and break them into pieces, then set them on fire in a safe way. After that, you can be sure that the data has been destroyed.

Your answer is on point sir BitMaxz, thanks for clearing my doubts.

Never save recovery seed words in any digital format on any devices, that applies for both phone and for computer, especially if they are connected to internet.
Even if you format hard drive there is a chance of having leftovers, stuff that can be recovered, or someone could steal this data before formating.
It's much safer to use simple paper to write words with pen, or you can use stainless steel metal if you want more protection from elements.

This is scary, it's not even safe to give your old SSD away to a friend or someone, if you have copied a very important file on the SSD before you aren't safe, no wonder some people prefer destroying the HDD or SSD when they are done with it.

Possible, like what mentioned above by BitMaxz. But i will describe it as very unlucky when some tech nerd get access your phone or laptop/computer by just what?
Stealing it? Getting it on a scraps? Or someone steal it then give it to him/her? I bet tech nerds won't do it.  That's why you're very unlucky if you experienced it that way.

But if you're talking to recover your files because you accidentally removed/deleted some files. Asking help to these nerds/experts will be very helpful.

I can even scan my old deleted files in a common recovery software out there even if it was formatted, some were corrupted but some were still.....interactable.
Like BitMaxz mentioned, it is still possible regardless.

This is why you should not store your recovery seed in a digital storage. Write it down as much as possible and hide it in somewhere safe. I hope your phone is safe as you asked though.

If you have this doubt, to avoid any risk/danger just move your coin from the keys that you have used with your phone. I think this is the simplest and quick solution you can implement. Of course as other used said a phone Is not a good solution for storage or creation of keys

It's depends on the phone, because some of the android phone's when it get formatted majority of the information will be wiped even though the hard drive is been uprooted they will not be a relevant or possible to get informationa that comes from the hard drive. While iphone secure much information. Except that the target of someone stole your phone is to really access your documents through your phone, the possiblity is there to recover all the necessary information if it's desperat. So my advice is that, it's not good save or store the information of your seed phrase in your phone.

Most thieves usually only focus on stealing and then selling the phones. And most sellers will also do the same thing, focusing more on how to resell the phone so that the money can roll back and make a profit.
Usually they are very rare to want to check, especially curious to restore the files on the phone. Maybe they won't think about it because of how much they get from buying and selling devices.
However it will be different if:
- The thief is someone who knows you, knows that your phone is used and contains important things so he will find a way to recover some data
- Or if someone deliberately wants to know various files or data from previous users of phones.
If that's the case, it's risky

Btw does this applicable to different phones or brands. What if the phone is an iphone, I think the security of that is a bit more higher compared to android phones. But knowing this things is quite helpful. I thought also that reformatting can be safe already but still there are some exceptions to that.

Its dangerous if someone with experience on this targeted high profile crypto persons.

I have not heard of it that phone was stolen and the phone which was formatted, later the files were recovered. I have not even heard that lost files in phone can be recovered. But BitMaxz explanation is very nice. But if it is hdd, I know that it can be recovered because there is an recovery software. The last time I used factory reset method to format the phone because I forgot the screen lock password, after formating the phone, and I was thinking that the password would wiped out but it was a surprised for me that the password was still inside which the phone was still locked so I have to to the phone a mobile phone repairer. And I paid for the service and format the phone with a laptop. And I told him to recover my files but he told me that the process is too combasome I would have to pay extra fee so I just left it and install the necessary apps back.

There are so many tutorials on how to unlock a phone lock that today almost anyone can do it without the help of an expert, although you should always be careful because there are a lot of software that are used for that purpose, and apart from being malicious, any such procedure can brick the phone. Also, many people today use facial recognition unlocking, which, like fingerprint unlocking, can be misused when a person is asleep or unaware of their actions. This is just one more reason that we do not consider these types of protection to be safe.

Since iOS 12 the trick of formatted data that wasn't written on it doesn't work anymore because of how APFS works, once the file is deleted the key is also, plus a long time ago iOS started encrypting the file system with a second key based on the first lock in user. So once you erase it with "erase Iphone" there is no way for someone to actually read the data even if recoverable, the only way to do it is from your backup.
That doesn't mean you should use your Iphone to store your keys either.


Just give them a bath in some descale or soon to banned in the EU cheap toilet bowl clear that is full of H2SO4 and HCL and throw them in the garbage bin. ;D Don't you think it's riskier to have them all in one place is some burglar gets in?

[Guide] Secure air-gapped crypto wallet storage method (https://bitcointalk.org/index.php?topic=2828437.0)

Using air-gapped device to store your crypto wallet is good and if you don't use it, you should use paper (or other physical materials like metal sheets, etc.) to store your seeds. After that, you must store them in a secure and safe place like in a vault.

Crypto Security - Additional Protection For Your Seed/Private Keys. (https://bitcointalk.org/index.php?topic=5230920.0)

One of the reason why it never good to store anything important information like seed phrase,password or even bank account details since anything you put on your put can be retrievable by experts on gadgets. So better at early save your password or anything important on offline like book or anything can be access online or thru your devices.

It's not that they are easily accessible somewhere in a drawer - something was learned from the example of the unfortunate man whose hard drive was allegedly thrown in the trash by his partner (Howells). In addition, I have taken certain security measures to deter burglars, and if they do decide to come to visit, they won't have a good time, that's for sure.

File recovery is not limited to SD cards, it can also work on hard disk drives and USBs (but not SSDs) that have a freshly cleared filesystem, though obviously a different tool is necessary to make use of that.

I can't remember how many old wallet files I've deleted from Phone and PC so far, but I can absolutely confirm that they won't be of any value anymore as no assets are stored on any of them. But fortunately so far I have never sold anything, be it my old Phone or notebook, it is still stored and has not been touched to this day.

After reading this one then I think one sure solution for me is to burn everything instead of selling it. Of course there are risks that we never think about selling them to a dealer even if they are formatted, but burning them is at least safe if it is no longer in use.

I'm not sure formatted files can be recovered 100% from memory, ssd or other devices, I have tried to recover some deleted files in 1 week duration and only 30% of files can be recovered if we don't do regular cleaning on PC/mobile device. But if you doubt the file can be recovered then use a backup storage device to move important files, so you don't worry if you lose your phone or even you can replace the purchased phone to the latest version

Files can be still recoverable for IOS12 but u3tools can clean/wipe your iPhone it uses Anti-recovery flash mode to clean and destroy personal data.
Time is fast technology keeps developing even if it is encrypted in the future hackers crackers can able to develop software that can decrypt recovered files from iPhones. So if you are going to give it to someone and don't want to expose your old important files that you recently deleted always use the Anti-recovery flash mode to fully destroy and clean your iPhone storage.

But why? You can't be 100% certain you won't accidentally reuse an old address in the future, or someone who sent you coins to one of your old addresses won't send coins to that address again in the future, assuming you still have access to it. If it's a wallet on your phone or PC, as you say, then you have nothing to lose by keeping a copy just in case. The file will be few megabytes at most. In the words of Satoshi:

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The other way around this issue is to use full disk encryption, which I use on all my devices. If you use a strong enough decryption key, then it doesn't matter if you leave some data behind after shredding, as it will be meaningless to anyone who is able to recover it.

o_e_l_e_o, thanks for reminding me of that post and yes I won't argue that it was good advice from then till now. What is clear I have saved some important files and also deleted quite a lot from the previous device that I can no longer use. However I don't plan on destroying the device in any way so far as my warehouse is still safe enough to hold more used stuff.

I also have 2 flashdisk currently to store important data. I check it regularly because I think there is a possibility about a device malfunction that could lose my data there. But over the last few years, it's still safe.