National Identification Number - Belgium

Belgium

In Belgium every citizen has a National Number, which is created by using the citizen's date of birth (encoded in six digits), followed by a serial number (three digits) and a checksum (two digits). The serial number is used so that men get the odd numbers, while women get the even numbers; thus, there can be only 500 men or women on each day.

The national number is unique to each person and in that capacity used by most government institutions; however, because one can immediately read the date of birth and the sex of the numbers' holder and because it is the key in most government databases (including that of the tax administration, the social security, and others), it is considered a privacy-sensitive number. For that reason, although it is put on the identity card by default, with the old ID cards a citizen could request that this would not be done. With the newer Digital ID cards that Belgium is rolling out now, however, this is no longer possible, since the National Number is used as the serial number for the private cryptography keys on the card.