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Subject: Re: GNU/Linux is Best for Secure File Deletion
Date: Sun, 14 Apr 2024 09:01:58 -0400
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On 4/14/2024 6:26 AM, Lazy Larry Piet wrote:
> On Sat, 13 Apr 2024 23:27:15 -0000 (UTC), vallor wrote:
> 
>>
>> SHRED(1)                 User Commands                 SHRED(1)
>>
>> NAME
>>         shred  -  overwrite a file to hide its contents, and op‐
>>         tionally delete it
>>
>> SYNOPSIS
>>         shred [OPTION]... FILE...
>>
>> DESCRIPTION
>>         Overwrite the specified FILE(s) repeatedly, in order  to
>>         make  it harder for even very expensive hardware probing
>>         to recover the data.
>>
> 
> srm is much better:
> 
> DESCRIPTION
>         srm  is  designed to delete data on mediums in a secure manner which can not be recovered by
>         thiefs, law enforcement or other threats.  The wipe algorythm is based on the paper  "Secure
>         Deletion  of Data from Magnetic and Solid-State Memory" presented at the 6th Usenix Security
>         Symposium by Peter Gutmann, one of the leading civilian cryptographers.
> 
>         The secure data deletion process of srm goes like this:
> 
>         *      1 pass with 0xff
> 
>         *      5 random passes. /dev/urandom is used for a secure RNG if available.
> 
>         *      27 passes with special values defined by Peter Gutmann.
> 
>         *      5 random passes. /dev/urandom is used for a secure RNG if available.
> 
>         *      Rename the file to a random value
> 
>         *      Truncate the file
> 
>         As an additional measure of security, the file is opened in O_SYNC mode and after each  pass
>         an fsync() call is done.  srm writes 32k blocks for the purpose of speed, filling buffers of
>         disk caches to force them to flush and overwriting old data which belonged to the file.
> 
> ==========



38 passes?  Ridiculous (if it does that many on all types of drives). 
Totally unnecessary and way too slow.


Gutmann's method is also worthless in some cases:
Table 3
https://www.usenix.org/legacy/events/fast11/tech/full_papers/Wei.pdf



Gutmann himself disavowed the use of 35 passes:

"performing the full 35-pass overwrite is pointless for any drive since 
it targets a blend of scenarios involving all types of (normally-used) 
encoding technology, which covers everything back to 30+-year-old MFM 
methods (if you don't understand that statement, re-read the paper). If 
you're using a drive which uses encoding technology X, you only need to 
perform the passes specific to X, and you never need to perform all 35 
passes."

He recommends shred for Linux, and the FOSS program Eraser for Windows
(https://eraser.heidi.ie)

https://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html#Epilogue


Next time do some research before making another of your clownish claims.