windows - How do 25-character product keys work? -


microsoft products , other products have product key 5 groups of 5 characters, this:

abcde-12345-abcde-12345-vwxyz

how product know if key valid? sort of cryptography? there library if want use kind of product key in code?

you might want have @ this article on how implement serial number validation function. goes advanced techniques such how keep on top of keygens, leaked keys, etc.

in short, there typically 3 underlying fields in such key:

  • the actual serial number, article calls "seed"
  • some verification data; part of verification data checked code
  • a checksum, crc or other simple typo-proofing mechanism

by implementing part of verification data checking in code, can things "genuine validation" (in case rest of verification happens on server) or trip keygens checking different subsets of validation data in new releases.


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