I've seen this all over the place: Download here! SHA1 = 8e1ed2ce9e7e473d38a9dc7824a384a9ac34d7d0 what does it mean? how does a hash come into play as far as downloads and... what use can I make of it? Is this a legacy item where you used to have to verify some checksum after you downloaded the whole file? Just curious, Cheers...
Hi, I'm working on an application where users have to make a call and type a verification number with the keypad of their phone. I would like to be able to detect if the number they type is correct or not. The phone system does not have access to a list of valid numbers, but instead it will validate the number against an algorithm (like...
I am writing some software to identify tracking numbers (in the same way that Google identifies FedEx or UPS numbers when you search for them). Most couriers use a system, such as a "weighted average mod system" which can be used to identify if a number is a valid tracking number. Does anyone know if TNT consignment numbers use such a sy...
I'm trying to check, using an automated discovery tool, when JAR files in remote J2EE application servers have changed content. Currently, the system downloads the whole JAR using WMI to checksum it locally, which is slow for large JARs. For UNIXy servers (and Windows servers with Cygwin), I can just log in over SSH and run md5sum foo.j...
Which checksum algorithm can you recommend in the following use case? I want to generate checksums of small JPEG files (~8 kB each) to check if the content changed. Using the filesystem's date modified is unfortunately not an option. The checksum need not be cryptographically strong but it should robustly indicate changes of any size. ...
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 o...
I'm putting together a script to find remove duplicates in a large library of images. At the moment I'm doing a two pass filter of first finding files of the same size and then doing a sha256 on a 10240 byte piece of the file to get a fingerprint of the files with the same size (code here). It works well, but I'm guessing there are prob...
I'm working with a small FAT16 filesystem, and I want to generate CRC values for indidual XML files which store configuration information. In case the data changes or is corrupted, I want to be able to check the CRC to determine that the file is still in it's original state. The question is, how do I put the CRC value into the file, wit...
Hi, Less than 10 client computers, each with their own installation have to upload data to a central server. The client database looks like: tblSales - rowGuid - randomNumber Central Server database: rowGuid randomNumber dateInserted I plan to use WCF to send the files to the central server. How can I verify the rows were insert...
Hi, does anybody know how to figure out the CRC algorithm if a given code + CRC string is given? I have got several strings consisting of code + matching CRCs but don´t know how to calculate the CRC in question so that I could produce more code strings. Here are some samples (16bit code + 4bit CRC): 0010101000011101 + 0000 0010101000011...
I want to programmatically create a SHA1 checksum of audio files (MP3, Ogg Vorbis, Flac). The requirement is that the checksum should be stable even if the header (eg. ID3) changes. Note: The audio files don't have CRCs This is what I tried by now: 1) Reading + Hashing all MPEG frames using Perl and MPEG::Audio::Frame my $sha1 = Diges...
Hello, I have a set of data protected by 16bit checksums that I need to correct. The checksum locations are known, the exact areas they are calculated on and the exact algorithm used to calculate them are not. 16bit, LSB first. I suspect it's some sort of 16bit CRC, but I have not been able to find the code that's actually calculatin...
Hi all, I find myself needing to generate a checksum for a string of data, for consistency purposes. The broad idea is that the client can regenerate the checksum based on the payload it recieves and thus detect any corruption that took place in transit. I am vaguely aware that there are all kinds of mathematical principles behind thi...
My understanding is that a hash code and checksum are similar things - a numeric value, computed for a block of data, that is relatively unique. i.e. The probability of two blocks of data yielding the same numeric hash/checksum value is low enough that it can be ignored for the purposes of the application. So do we have two words for t...
I'm on a Windows machine and I want to run a checksum on the MySQL distribution I just got. It looks like there are products to download, an unsupported Microsoft tool, and probably other options. I'm wondering if there is a consensus for the best tool to use. This may be a really easy question, I've just never run a checksum routine ...
I have recently started playing around with libnet and using it to generate IPV6 packets. I am very new at programming, however, I am quite happy with the library. I have one problem with it though. It seems that libnet currently does not have the ability to properly calculate checksums on IPV6 packets. Being so new to programming,...
I'm using the following set of values to create a 9 character long base 31 value: 0123456789ABCDEFGHJKLMNPQRTUWXY I was looking at modifying the Luhn algorithm to work with my base. My question is: In base 10, the Luhn algorithm doubles each value in an even position and then if the result is >10 the individual digits of the result ar...
Does IMAP protocol provide any way to validate / verify that complete message was transferred from the server to local client? i.e. is there any equivalent of ETag / MD5 or some other checksum? ...
I'm trying to interface with a 3rd party system and they have provided a code sample to calculate a CRC value when sending text data. The C code the vendor provided looks like this: #define CRCRES 0xf0b8 /* residue for good verify */ #define DEBUG unsigned crctbl[] = {0x0000, 0x1081, 0x2102, 0x3183, 0x4204, 0...
I want to compute a checksum of all of the values of a column in aggregate. In other words, I want to do some equivalent of md5(group_concat(some_column)) The problem with this approach is: It's inefficient. It has to concat all of the values of the column as a string in some temporary storage before passing it to the md5 function...