File Saving Options - Digests

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Temprecord stores an extra piece of information with every TRX data file called a digest.  A digest is effectively a number that is determined by looking at the logged samples and other data in the file and performing a calculation on that data.  The result of this calculation is called a digest.  The digest is designed so that:

•no two files will ever1 produce the same digest unless they are identical.

•changing even one data value only by the tiniest of amounts will result in the digest changing to a completely different value.

•there are a nearly infinite2 number of digests.

•unless you know the digest key, you can't3 "fake" a digest.

1. when we say "ever", we mean that it is extremely unlikely - to be precise, the chance of two different data sets generating the same digest value is one in 340,282,366,920,938,463,463,374,607,431,768,211,456.

2. when we say "nearly infinite", we mean a very large number (see 1. above)

3. when we say "can't fake" a digest, we mean that this strategy is unlikely to succeed, because the last step ("hand-tuning" the data set) will likely need to be performed a large number (yep, that big number again) of times to get the correct result.

•take delivery of a datafile.

•note what the digest of the file is.

•"tamper" with the file, e.g. use a text editor to alter potentially embarrassing or damaging values.

•"hand-tune" the data set so that when TRW calculates the digest of the data set it produces a digest that is the same as it was when you received it.