Checksum method determination

**Keith Thompson** · Feb 3 '06, 12:35 AM

Re: Checksum method determination

rjfjohnson@hotm ail.com writes:[color=blue]
> I am trying to communicate with serial device and I need to know the
> method used to calculate the 1digit checksum.[/color]
[snip]

This has nothing to do with the C programming language. Please limit
followups to sci.crypt, comp.programmin g, and sci.math, or to some
appropriate subset.

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

**Jeremy Boden** · Feb 3 '06, 12:55 AM

Re: Checksum method determination

In message <1138924840.653 965.143470@g43g 2000cwa.googleg roups.com>,
rjfjohnson@hotm ail.com writes[color=blue]
>Hey,
>
>I am trying to communicate with serial device and I need to know the
>method used to calculate the 1digit checksum.
>
>I have a commercial program that can communicate with the device, and a
>serial port sniffer, and so I am able to get any number of sample
>checksum digits. Below is a list of some.
>
>I keep finding patterns, and it seems to revolve around the magic
>number of 7.
>
>If anyone could please help find this out, or does anyone know of a
>brute-force method of determining a checksum?
>
>Thanks,
>Ryan Johnson.
>[/color]
.... <data snipped>

The 0 - 7 values would seem to indicate that you only get 3 bits back.
Note the results of inputting 8 or 9.
Perhaps you have some kind of shift register???

--
Jeremy Boden

**Luc The Perverse** · Feb 3 '06, 01:05 AM

Re: Checksum method determination

<rjfjohnson@hot mail.com> wrote in message
news:1138924840 .653965.143470@ g43g2000cwa.goo glegroups.com.. .[color=blue]
> If anyone could please help find this out, or does anyone know of a
> brute-force method of determining a checksum?[/color]

??? Your question doesn't even make sense. Are you sure you know what you
are asking?

Yes I am familiar with one way of bruteforcing a checksum but checksum
collisions could throw you off - of course it is the same way you bruteforce
just about anything.

--
LTP

:)

**rjfjohnson@hotmail.com** · Feb 3 '06, 01:05 AM

Re: Checksum method determination

Jeremy,

Thanks for your reply. In my efforts, I found some code for a BASIC
stamp which used something to do with shift registers... What exactly
are these?

Ryan

**Ian Collins** · Feb 3 '06, 01:05 AM

Re: Checksum method determination

rjfjohnson@hotm ail.com wrote:[color=blue]
> Hey,
>
> I am trying to communicate with serial device and I need to know the
> method used to calculate the 1digit checksum.
>[/color]
Not a language specific question, choose your groups with more care and
look up parity.

--
Ian Collins.

**Flash Gordon** · Feb 3 '06, 01:15 AM

Re: Checksum method determination

rjfjohnson@hotm ail.com wrote:[color=blue]
> Hey,
>
> I am trying to communicate with serial device and I need to know the
> method used to calculate the 1digit checksum.[/color]

<snip>

What is your C question? I don't read the other groups, so I can't
comment on topicality there, but on comp.lang.c we deal with the C
programming language, not general programming problems.

Once you know the appropriate algorithm and have hit problems
implementing it in standard C you can bring those problems to
comp.lang.c, but until you are at the point of having C problems it is
the wrong place.
--
Flash Gordon
Living in interesting times.
Although my email address says spam, it is real and I read it.

**rjfjohnson@hotmail.com** · Feb 3 '06, 02:25 AM

Re: Checksum method determination

Thank you,

The answer was to do with parity

temp XOR temp+1 where temp is the number

**Zara** · Feb 3 '06, 06:05 AM

Re: Checksum method determination

On 2 Feb 2006 16:00:40 -0800, rjfjohnson@hotm ail.com wrote:
[color=blue]
>Hey,
>
>I am trying to communicate with serial device and I need to know the
>method used to calculate the 1digit checksum.
>
>I have a commercial program that can communicate with the device, and a
>serial port sniffer, and so I am able to get any number of sample
>checksum digits. Below is a list of some.
>
>I keep finding patterns, and it seems to revolve around the magic
>number of 7.[/color]

You must take the xor of all digits of the number considered as binary
values in the range o-15. The resul soulb xor'ed with 7, and the
number added to char '0' to get the checksum char
For instance:

1255 | 4 => (1 ^ 2 ^5^5^7)+'0'='4'
8 | ? => (8^7)+'0'='?'

[color=blue]
>
>If anyone could please help find this out, or does anyone know of a
>brute-force method of determining a checksum?[/color]

Instinct, and some counts
[color=blue]
>
>Thanks,
>Ryan Johnson.
>
>
>[/color]

BTW, this thread seems completely off-topic

Best regrads,

Zara

**Nelu** · Feb 3 '06, 07:55 AM

Re: Checksum method determination

rjfjohnson@hotm ail.com wrote:[color=blue]
> Thank you,
>
> The answer was to do with parity
>
> temp XOR temp+1 where temp is the number
>[/color]
Please read http://cfaj.freeshell.org/google/
Thank you!

--
Ioan - Ciprian Tandau
tandau _at_ freeshell _dot_ org (hope it's not too late)
(... and that it still works...)

**Troky** · Feb 3 '06, 03:05 PM

Re: Checksum method determination

<rjfjohnson@hot mail.com> wrote in message
news:1138924840 .653965.143470@ g43g2000cwa.goo glegroups.com.. .[color=blue]
> Hey,
>
> I am trying to communicate with serial device and I need to know the
> method used to calculate the 1digit checksum.[/color]

It looks like chksum=7 XOR digit0 XOR digit1 XOR digit2....

**Shmuel (Seymour J.) Metz** · Feb 3 '06, 03:15 PM

Re: Checksum method determination

In <1138924840.653 965.143470@g43g 2000cwa.googleg roups.com>, on
02/02/2006
at 04:00 PM, rjfjohnson@hotm ail.com said:
[color=blue]
>I am trying to communicate with serial device and I need to know the
>method used to calculate the 1digit checksum.[/color]

Read the documentation on the serial device in question. Then google
for CRC, assuming that's what it uses.

--
Shmuel (Seymour J.) Metz, SysProg and JOAT <http://patriot.net/~shmuel>

Unsolicited bulk E-mail subject to legal action. I reserve the
right to publicly post or ridicule any abusive E-mail. Reply to
domain Patriot dot net user shmuel+news to contact me. Do not
reply to spamtrap@librar y.lspace.org

**anonymous** · Feb 4 '06, 12:05 AM

Re: Checksum method determination

On 2 Feb 2006 16:00:40 -0800, rjfjohnson@hotm ail.com wrote:
[color=blue]
>Hey,
>
>I am trying to communicate with serial device and I need to know the
>method used to calculate the 1digit checksum.
>
>I have a commercial program that can communicate with the device, and a
>serial port sniffer, and so I am able to get any number of sample
>checksum digits. Below is a list of some.
>
>I keep finding patterns, and it seems to revolve around the magic
>number of 7.
>
>If anyone could please help find this out, or does anyone know of a
>brute-force method of determining a checksum?
>
>Thanks,
>Ryan Johnson.
>
>
>
>1255 | 4
>1265 | 7
>1256 | 7
>1355 | 5
>3455 | 0
>2455 | 1
>1455 | 2
>455 | 3
>3355 | 7
>2355 | 6
>1355 | 5
>355 | 4
>255 | 5
>1255 | 4
>2255 | 7
>3255 | 6
>4255 | 1
>425 | 4
>1 | 6
>2 | 5
>3 | 4
>4 | 3
>5 | 2
>6 | 1
>7 | 0
>8 | ?
>9 | >
>10 | 6
>11 | 7
>12 | 4
>13 | 5
>14 | 2
>15 | 3
>16 | 0
>17 | 1
>18 | >
>19 | ?
>21 | 4
>23 | 6
>2 | 5
>22 | 7
>222 | 5
>3333 | 7
>
>3 | 4
>33 | 7
>333 | 4
>3333 | 7
>
>12345678912345 6789 | 9
>
>45 | 6
>56 | 4
>3567 | 0
>3566 | 1
>356 | 7
>1234 | 3
>123 | 7[/color]

Newby question isn't a checksum of one digit inadequate for a serial
transmission?

It would be like dividing 474656229 by 15108777 and validating on a
single MSD wouldn't it?

**Joe Wright** · Feb 4 '06, 12:35 AM

Re: Checksum method determination

anonymous wrote:[color=blue]
> On 2 Feb 2006 16:00:40 -0800, rjfjohnson@hotm ail.com wrote:
>
>[color=green]
>>Hey,
>>
>>I am trying to communicate with serial device and I need to know the
>>method used to calculate the 1digit checksum.
>>
>>I have a commercial program that can communicate with the device, and a
>>serial port sniffer, and so I am able to get any number of sample
>>checksum digits. Below is a list of some.
>>
>>I keep finding patterns, and it seems to revolve around the magic
>>number of 7.
>>
>>If anyone could please help find this out, or does anyone know of a
>>brute-force method of determining a checksum?
>>
>>Thanks,
>>Ryan Johnson.
>>
>>
>>
>>1255 | 4
>>1265 | 7
>>1256 | 7
>>1355 | 5
>>3455 | 0
>>2455 | 1
>>1455 | 2
>>455 | 3
>>3355 | 7
>>2355 | 6
>>1355 | 5
>>355 | 4
>>255 | 5
>>1255 | 4
>>2255 | 7
>>3255 | 6
>>4255 | 1
>>425 | 4
>>1 | 6
>>2 | 5
>>3 | 4
>>4 | 3
>>5 | 2
>>6 | 1
>>7 | 0
>>8 | ?
>>9 | >
>>10 | 6
>>11 | 7
>>12 | 4
>>13 | 5
>>14 | 2
>>15 | 3
>>16 | 0
>>17 | 1
>>18 | >
>>19 | ?
>>21 | 4
>>23 | 6
>>2 | 5
>>22 | 7
>>222 | 5
>>3333 | 7
>>
>>3 | 4
>>33 | 7
>>333 | 4
>>3333 | 7
>>
>>1234567891234 56789 | 9
>>
>>45 | 6
>>56 | 4
>>3567 | 0
>>3566 | 1
>>356 | 7
>>1234 | 3
>>123 | 7[/color]
>
>
>
> Newby question isn't a checksum of one digit inadequate for a serial
> transmission?
>
> It would be like dividing 474656229 by 15108777 and validating on a
> single MSD wouldn't it?[/color]

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

**Joe Wright** · Feb 4 '06, 12:35 AM

Re: Checksum method determination

anonymous wrote:[color=blue]
> On 2 Feb 2006 16:00:40 -0800, rjfjohnson@hotm ail.com wrote:
>
>[color=green]
>>Hey,
>>
>>I am trying to communicate with serial device and I need to know the
>>method used to calculate the 1digit checksum.
>>
>>I have a commercial program that can communicate with the device, and a
>>serial port sniffer, and so I am able to get any number of sample
>>checksum digits. Below is a list of some.
>>
>>I keep finding patterns, and it seems to revolve around the magic
>>number of 7.
>>
>>If anyone could please help find this out, or does anyone know of a
>>brute-force method of determining a checksum?
>>
>>Thanks,
>>Ryan Johnson.
>>
>>
>>
>>1255 | 4
>>1265 | 7
>>1256 | 7
>>1355 | 5
>>3455 | 0
>>2455 | 1
>>1455 | 2
>>455 | 3
>>3355 | 7
>>2355 | 6
>>1355 | 5
>>355 | 4
>>255 | 5
>>1255 | 4
>>2255 | 7
>>3255 | 6
>>4255 | 1
>>425 | 4
>>1 | 6
>>2 | 5
>>3 | 4
>>4 | 3
>>5 | 2
>>6 | 1
>>7 | 0
>>8 | ?
>>9 | >
>>10 | 6
>>11 | 7
>>12 | 4
>>13 | 5
>>14 | 2
>>15 | 3
>>16 | 0
>>17 | 1
>>18 | >
>>19 | ?
>>21 | 4
>>23 | 6
>>2 | 5
>>22 | 7
>>222 | 5
>>3333 | 7
>>
>>3 | 4
>>33 | 7
>>333 | 4
>>3333 | 7
>>
>>1234567891234 56789 | 9
>>
>>45 | 6
>>56 | 4
>>3567 | 0
>>3566 | 1
>>356 | 7
>>1234 | 3
>>123 | 7[/color]
>
>
>
> Newby question isn't a checksum of one digit inadequate for a serial
> transmission?
>
> It would be like dividing 474656229 by 15108777 and validating on a
> single MSD wouldn't it?[/color]

--
Joe Wright
"Everything should be made as simple as possible, but not simpler."
--- Albert Einstein ---

Checksum method determination

Checksum method determination

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