Do you know what a checksum is?

[jonbeeza]

I did not know, until I read up on it last night, and pretty clever whoever thought it up.

Because I collect certain items I like to check serial numbers, to help me find out how old an item is and where it was manufactured . I have often wondered how some companies come by their method of allocating numbers, not necessarily serial numbers but some other numbers, such as those allocated to people, such as NHS Numbers. It was fascinating to learn how numbers are allocated, but also that the last digit of such a numbering system, is in fact a check sum digit, to verify that the numbers before the checksum digit are correct. This is done by a calculation method.

Examples given include 987 654 4321

The method calculation for a ten digit number is below ,and using 943 476 5919 as an example.

• The first digit is 9. This is multiplied by 10.
• The second digit is 4. This is multiplied by 9.
• And so on until the ninth digit (1) is multiplied by 2.
• The result of this calculation is summed. In this example: 9*10+4*9+3*8+4*7+7*6+6*5+5*4+9*3+1*2 = 299.
• The remainder when dividing this number by 11 is calculated, yielding a number in the range 0–10, which would be 2 in this case.
• Finally, this number is subtracted from 11 to give the checksum in the range 1–11, in this case 9, which becomes the last digit of the NHS number.
• A checksum of 11 is represented by 0 in the final NHS number. If the checksum is 10 then the number is not valid

I thought it is pretty simple, and clever. Sorry if anyone's head hurts.

 

[onomatopoeia]

Commonplace in computing with various different algorithms in use. See also parity bits for something much simpler.

 

[KIPAX]

I think blockchains are an extension of this ...the checksum is in the next blockchain.. hashed of course.. so the chain cant be broken or changed ...

 

[jonbeeza]

I always thought such numbers were picked at random, and whatever the next sequential number came next, was given out / allocated. But this is not always the case, a calculation process takes place first, to make sure the numbers are correct.

 

[jonbeeza]

I think blockchains are an extension of this ...the checksum is in the next blockchain.. hashed of course.. so the chain cant be broken or changed ...

I did think about mining a little while ago, and after trying to read up on the math's behind it, I gave up on it. It was just too complex for my brain to comprehend, as there would probably be a flaw in it, and and many would lose on it. I suppose it's the same with anything, to have winners you must have losers.

 

[JonathanRyan]

Commonplace in computing with various different algorithms in use. See also parity bits for something much simpler.

I wish this were still true......used to be common (e.g. credit card numbers) but I had a conversation with people who designed a system that involved manual keying of policy numbers into a claim about how many errors they were getting. "What's your checksum algo?" My what now? Their numbers start at 1 and go up.........................

Lots of routines exist though - some are really clever and designed to check when somebody has miskeyed a number by giving different weight to digits so that if they key 135679 it might know that they really meant 153679.

Wait until you learn about trapdoor algorithms.. Trapdoor function - Wikipedia

 

[jonbeeza]

I wish this were still true......used to be common (e.g. credit card numbers) but I had a conversation with people who designed a system that involved manual keying of policy numbers into a claim about how many errors they were getting. "What's your checksum algo?" My what now? Their numbers start at 1 and go up.........................

Lots of routines exist though - some are really clever and designed to check when somebody has miskeyed a number by giving different weight to digits so that if they key 135679 it might know that they really meant 153679.

Wait until you learn about trapdoor algorithms.. Trapdoor function - Wikipedia

The last digit of the number, is supposed to prevent / identify incorrect numbers. But in reality, would anybody actually scrutinise the checksum digit? Probably not, but still a clever and simple method to implement.

 

[jonbeeza]

You will have to excuse this thread, it is just the way my weird mind works. Besides, I like to check the serial numbers of my collectable items, it gives me an idea when and where an item was manufactured. This can help with reassuring others to the authenticity and age of an item.

 

[JonathanRyan]

But in reality, would anybody actually scrutinise the checksum digit?

Computers check them

 

[Cobra]

Computers check them

Do they check them all or just check sum?
Sorry

 

[AndrewFlannigan]

Sum just like numbers...

 

[Mr Bump]

I worked an IT contract a few years ago on a very high security system where all the files in the entire environment had there checksums recorded so no no authorised files could be accessed or run, it was a mammoth task to keep it all in shape.

 

[jonbeeza]

I worked an IT contract a few years ago on a very high security system where all the files in the entire environment had there checksums recorded so no no authorised files could be accessed or run, it was a mammoth task to keep it all in shape.

I remember when I was in school back in the day, they were just bringing in IT, most did not understand what it was. I wish I had of studied it way back then, I suppose not many of us realised just how far IT would go. Obviously, the smart kids could see where the future would end up.

 

[onomatopoeia]

I remember when I was in school back in the day, they were just bringing in IT, most did not understand what it was. I wish I had of studied it way back then, I suppose not many of us realised just how far IT would go. Obviously, the smart kids could see where the future would end up.

I did, pretty much as soon as I got a ZX81 when I was 12. My school didn't offer any computing subject at O level or A level though, so I did computer systems engineering at university.

 

[jonbeeza]

I did, pretty much as soon as I got a ZX81 when I was 12. My school didn't offer any computing subject at O level or A level though, so I did computer systems engineering at university.

I wish I had of done a computing course, that is the way of things today. It is not enough being literate, computing literacy is a big bonus, seeing the way the world is moving today.