Tagasta

Tagasta is a word that appears primarily in the context of Estonian personal identification codes (isikukood). Specifically, it refers to the checksum digit, or the last digit of the 11-digit isikukood. This digit is calculated based on a complex algorithm applied to the preceding ten digits, serving to validate the integrity of the code and detect errors introduced during data entry.

The primary purpose of the Tagasta is to prevent accidental or deliberate falsification of the isikukood. By recalculating the checksum digit and comparing it to the existing one, systems can verify the validity of the identification code.

The calculation of the Tagasta involves a weighted sum of the first ten digits, followed by a modulo operation. The specific weighting sequence and modulo divisor used are key components of the checksum algorithm. If the result of the calculation differs from the existing last digit, the isikukood is deemed invalid.

While commonly referred to as simply the "last digit" or "checksum digit," the term "Tagasta" provides a more specific and technical designation for this crucial element of the Estonian personal identification system. It underscores the digit's role in ensuring the accuracy and reliability of individual identification within Estonia.