checksum

I'm using the chechsum function in sql server 2008 R2 and I would like to get the same int values in a C# app. Is there any equivalent method in c# that returns the values like the sql checksum function? Thanx CHECKSUM docs don't disclose how it computes the hash. If you want a hash you can use in T-SQL and C#, pick from the algorithms supported in HashBytes On SQL Server Forum, at this page , it's stated: The built-in CHECKUM function in SQL Server is built on a series of 4 bit left rotational xor operations. See this post for more explanation. I was able to port the BINARY_CHECKSUM to c# and

Background: I have a section of memory, 1024 bytes. The last 1020 bytes will always be the same. The first 4 bytes will change (serial number of a product). I need to calculate the CRC-16 CCITT (0xFFFF starting, 0x1021 mask) for the entire section of memory, CRC_WHOLE . Question: Is it possible to calculate the CRC for only the first 4 bytes, CRC_A , then apply a function such as the one below to calculate the full CRC? We can assume that the checksum for the last 1020 bytes, CRC_B , is already known. CRC_WHOLE = XOR(CRC_A, CRC_B) I know that this formula does not work (tried it), but I am

I am using following code to implement Luhn algorithm for credit card check in c# language but could not get the output to generate the check sum its showing validity: kindly help me.Thank you in advance public class Program { private static void Main(string[]creditcard) { int sum = 0, d; string num ="7992739871"; int a = 0; for (int i = num.Length - 2; i >= 0; i--) { d = Convert.ToInt32(num.Substring(i, 1)); if (a % 2 == 0) d = d * 2; if (d > 9) d -= 9; sum += d; a++; } if ((10 - (sum % 10) == Convert.ToInt32(num.Substring(num.Length - 1)))) Console.WriteLine("valid"); Console.WriteLine("sum

Let's assume that I have some packets with a 16-bit checksum at the end. I would like to guess which checksum algorithm is used. For a start, from dump data I can see that one byte change in the packet's payload totally changes the checksum, so I can assume that it isn't some kind of simple XOR or sum. Then I tried several variations of CRC16 , but without much luck. This question might be more biased towards cryptography, but I'm really interested in any easy to understand statistical tools to find out which CRC this might be. I might even turn to drawing different CRC algorithms if

I'm looking for a solution to generate a checksum for any type of Java object, which remains the same for every execution of an application that produces the same object. I tried it with Object.hashCode() , but the api says ....This integer need not remain consistent from one execution of an application to another execution of the same application. I had similar problem (generating good hashcode for XML files) and I found out that the best solution is to use MD5 through MessageDigest or in case you need something faster: Fast MD5 . Please notice that even if Object.hashCode would be the same

I'm looking for a modern JavaScript implementation of CRC32. This implementation , which may have originated from here , and is now here, there and everywhere , is unacceptable because it's slow (500ms/MB), and depends on over 2KB of space delimited table, accessed using substr. Yuck! There appears to be a few variations of CRC32, so I need to match this output: mysql> SELECT CRC32('abcde'); > 2240272485 Function doesn't actually need to accept a string however, since I'm working with byte arrays. Update I added a helper function to create the CRCTable instead of having this enormous literal

Maybe I'm just not seeing it, but CRC32 seems either needlessly complicated, or insufficiently explained anywhere I could find on the web. I understand that it is the remainder from a non-carry-based arithmetic division of the message value, divided by the (generator) polynomial, but the actual implementation of it escapes me. I've read A Painless Guide To CRC Error Detection Algorithms , and I must say it was not painless. It goes over the theory rather well, but the author never gets to a simple "this is it." He does say what the parameters are for the standard CRC32 algorithm, but he

Does anyone know of a way to compare two .NET assemblies to determine whether they were built from the "same" source files? I am aware that there are some differencing utilities available, such as the plugin for Reflector, but I am not interested in viewing differences in a GUI, I just want an automated way to compare a collection of binaries to see whether they were built from the same (or equivalent) source files. I understand that multiple different source files could produce the same IL, and realise that the process would only be sensitive to differences in the IL, not the original source.