[Cryptography] Digital dyes for tracing digital leaks ?

[Tom Mitchell]

On Thu, Jan 10, 2019 at 8:22 AM Henry Baker <hbaker1 at pipeline.com> wrote:

> If I'm trying to find a leak in my sewer or water pipe, I
> can choose from a large variety of colored and/or fluorescent
> dyes, which are easily detected when they appear outside the
> pipe.
>
> Ditto for radioactive tracers for even tinier leaks.
>
> Are there standard digital *codes* (other than 0xdeadbeef)
>

No standard codes.  Much depends on the data and data structures.

I have seen off by one address get stuffed in memory.  If the system
wants word addresses to be aligned then adding one to a pointer thing could
trigger an exception.  This works for return stacks and structures of
pointers
and such but not data.

Data knowledge allows initializing or dismissing data and tagging it with
known to be impossible floating point numbers...  Even.. standard special
numbers.
i.e. the US population is less than 1 billion and not negative.  Time of day
structures set to epoch + 7 seconds or some impossible date in prehistory.

   - There are separate *positive and a negative zero* values, differing in
   the sign bit, where all other bits are 0. These must be considered equal
   even though their bit patterns are different.
   - There are special *positive and negative infinity* values, where the
   exponent is all 1-bits and the significand is all 0-bits. These are the
   results of calculations where the positive range of the exponent is
   exceeded, or division of a regular number by zero.
   - There are special *not a number* (or NaN) values where the exponent is
   all 1-bits and the significand is *not* all 0-bits. These represent the
   result of various undefined calculations (like multiplying 0 and infinity,
   any calculation involving a NaN value, or application-specific cases). Even
   bit-identical NaN values must *not* be considered equal.

NaN handing is handy... Too often code ignores floating exceptions like
divide by zero.
Data structures can be expanded to include a tag: white, black, grey in the
style of garbage collecting.
Perhaps with an ifdef DEBUG preprocessor  and assert()


-- 
   T o m    M i t c h e l l
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