Check Sums

[+CachemanCando]

I'm figuring out an ? cache. I think I have the figured out the coordinates. The cache owner has posted checksums. Can someone enlighten me how these are used? Is there a tutorial posted somewhere. Still getting my feet wet in this game. Thanks in advance!

[+DocDiTTo]

Typically you add up whatever numbers you came up with and see if that total matches the checksum provided by the cache owner. Usually the owner tells you in the cache page what to do, but if not this is the "default" way of doing it.

Edited February 2, 2006 by DocDiTTo

[+CachemanCando]

Thanks for the info ... Hmmm ... maybe I don't have the right coords then ... back to doing the math again ...

[Clan Riffster]

Kinda like N12* 34.567 W89* 12.345. Add 1+2+3+4, etc. Check sum would be 60. Some folks will specify that you add the number groupings together, like 12+34+567, etc for a check sum of 1059. If you see a large check sum, try the second method.

[+fizzymagic]

Not too long ago, I added checksum calculation into GeoCalc. It does both the kind described above and the kind described by NotThePainter below (his kind is known as a "digital root").

Edited February 2, 2006 by fizzymagic

[+NotThePainter]

I have a puzzle cache (80 Feet of Waterline Nicely Making Way) where the checksums that I originally gave along with a radius were too good. People were able to find the cache without finding all of the middle points.

 

I've since gone to a "harder" checksum. When you compute the checksum you keep on going until you only have 1 digit left. So your "60" example still needs more addition, 6 + 0 = 6.

 

So there are other ways to do them but hopefully the hider tells you what to do!

 

Paul

[+CachemanCando]

Not too long ago, I added checksum calculation into GeoCalc.  It does both the kind described above and the kind described by NotThePainter below (his kind is known as a "digital root").

I redid the math and I now get the same checksums the author posted.

 

I'm encouraged by seeing your program comes up with the same sums!

Your program has more information than I think I will ever understand!

 

I'm finding this technology can be a humbling, but I am awed by it, so I keep plugging along learning new things along the way.

 

Thanks for all your input! Now to see if I can bag this cache!

[+reveritt]

I have a puzzle cache (80 Feet of Waterline Nicely Making Way) where the checksums that I originally gave along with a radius were too good. People were able to find the cache without finding all of the middle points.

 

I've since gone to a "harder" checksum. When you compute the checksum you keep on going until you only have 1 digit left. So your "60" example still needs more addition, 6 + 0 = 6.

 

So there are other ways to do them but hopefully the hider tells you what to do!

 

Paul

One way to avoid a giveaway is to provide onnly the last digit of the checksum. There is a low probability that someone could get the same last digit using inncorrect coordinates, but a much lower probability that they will be able to figure out the coordinates from the checksum.

[+fizzymagic]

One way to avoid a giveaway is to provide onnly the last digit of the checksum.

This method is somewhat easier to calculate than the digital root, but turns out to contain almost exactly the same information:

 

The last digit of the checksum S is S mod 10

 

The digital root of checksum S is 1 + ((S - 1) mod 9)

 

There are two main advantages of the digital root as a checksum: first, the digital root of the sum of two numbers is equal to the digital root of the sum of the numbers' digital roots:

 

DR(x + y) = DR(DR(x) + DR(y))

 

And second, the digital root of a number multiplied by 10 is the same as the digital root of the original number:

 

DR(10 x) = DR(x)

 

That allows you to do digital roots a a little bit at a time.

 

For example, to get the digital root of a huge number you can break it up into pieces, calculate the digital root of each piece, and then take the digital root of all those digital roots.

 

I am guessing that this is far more than anyone ever wanted to know about using digital roots as checksums. Just don't get me started on checksums in general.

[+Moose Mob]

One way to avoid a giveaway is to provide onnly the last digit of the checksum.

This method is somewhat easier to calculate than the digital root, but turns out to contain almost exactly the same information:

 

The last digit of the checksum S is S mod 10

 

The digital root of checksum S is 1 + ((S - 1) mod 9)

 

There are two main advantages of the digital root as a checksum: first, the digital root of the sum of two numbers is equal to the digital root of the sum of the numbers' digital roots:

 

DR(x + y) = DR(DR(x) + DR(y))

 

And second, the digital root of a number multiplied by 10 is the same as the digital root of the original number:

 

DR(10 x) = DR(x)

 

That allows you to do digital roots a a little bit at a time.

 

For example, to get the digital root of a huge number you can break it up into pieces, calculate the digital root of each piece, and then take the digital root of all those digital roots.

 

I am guessing that this is far more than anyone ever wanted to know about using digital roots as checksums. Just don't get me started on checksums in general.

Do we need a "Math speaking" forum like we have for French and German?

[SPKr]

One way to avoid a giveaway is to provide onnly the last digit of the checksum.

This method is somewhat easier to calculate than the digital root, but turns out to contain almost exactly the same information:

 

The last digit of the checksum S is S mod 10

 

The digital root of checksum S is 1 + ((S - 1) mod 9)

 

There are two main advantages of the digital root as a checksum: first, the digital root of the sum of two numbers is equal to the digital root of the sum of the numbers' digital roots:

 

DR(x + y) = DR(DR(x) + DR(y))

 

And second, the digital root of a number multiplied by 10 is the same as the digital root of the original number:

 

DR(10 x) = DR(x)

 

That allows you to do digital roots a a little bit at a time.

 

For example, to get the digital root of a huge number you can break it up into pieces, calculate the digital root of each piece, and then take the digital root of all those digital roots.

 

I am guessing that this is far more than anyone ever wanted to know about using digital roots as checksums. Just don't get me started on checksums in general.

Do we need a "Math speaking" forum like we have for French and German?

My calculator just exploded.

 

And I have a headache.

 

[+reveritt]

One way to avoid a giveaway is to provide onnly the last digit of the checksum.

This method is somewhat easier to calculate than the digital root, but turns out to contain almost exactly the same information:

...

But from a purely practical viewpoint--as a way to check the solution to a cache puzzle--this is a bit involved, don't you agree?

[+AuntieWeasel]

My frontal lobes just exploded.

[+fizzymagic]

But from a purely practical viewpoint--as a way to check the solution to a cache puzzle--this is a bit involved, don't you agree?

No. Calculating the digital root is easy, as explained by the first poster above. You just sum all the digits, and then, if there is more than one digit in the sum, you sum those digits, repeating until you are left with one digit.

 

I was just showing some of the properties of the result of that process.

[+sept1c_tank]

Of course you were!

[+reveritt]

But from a purely practical viewpoint--as a way to check the solution to a cache puzzle--this is a bit involved, don't you agree?

No. Calculating the digital root is easy, as explained by the first poster above. You just sum all the digits, and then, if there is more than one digit in the sum, you sum those digits, repeating until you are left with one digit.

 

I was just showing some of the properties of the result of that process.

I've got one digit for you!

 

But seriously now, it is clear that any child can do the arithmetic, but as you can see, it frightens people away.

 

Look at some of the responses in this thread (or any discussion that involves math). Intelligent people who are confident, and articulate in verbal communication are flummoxed by the simplest math, and feel the need to say so. I've never understood that need.

 

There are many subjects about which I know little or nothing. Sometimes (as many people know) I offer my opinion on them anyway. If the topic seems interesting, I might ask for an explanation. More often, I just do not comment. But never do I step into the conversation just to say that I am totally ignorant (although this may nonetheless become apparent).

 

Take sports, for example. Words cannot express the depth of my ignorance (and indifference). I cannot imagine jumping into a sports-related discussion just to say "gosh, I have no clue what you are talking about". I think that is typical of most people with regard to most topics--except mathematics.

 

Why is that?

[+sept1c_tank]

...Intelligent people who are confident, and articulate in verbal communication are flummoxed by the simplest math, and feel the need to say so.  I've never understood that need.

Along the same lines, some people are so stymied with the insertion of a foreign language into their private little world, they actually get mad about it...and tell you just how mad it makes them.

[+Wacka]

If you think fizzymagic's math was hard on his post, take a look at some of his puzzle caches!