Unique citizenship number

The uniform civil number (Bulgarian: Единен граждански номер; abbreviated: ЕГН, EGN) is a 10-digit unique number assigned to each Bulgarian citizen or resident foreign national. It serves as a national identification number. An EGN is assigned to Bulgarians at birth, or when a birth certificate is issued. The uniform system for civil registration and administrative service of population (Bulgarian: Единна система за гражданска регистрация и административно обслужване на населението; abbreviated: ЕСГРАОН, ESGRAON) regulates the EGN system.

Structure

The initial six digits correspond to the birth date (YYMMDD). Since there are only two digits reserved for the year, only years between 1900 and 1999 can be encoded directly. Other years get represented as follows:

The next three digits designate the birth order number, the third digit being even for males and odd for females. Each district is assigned a range of three-digit numbers, used consecutively, altering even and odd numbers between males and females born on the particular day. In rare cases, numbers are "borrowed" from an adjacent district.

The tenth digit is a checksum, calculated using the following algorithm:

  1. Each digit is multiplied by its weight (see below)
  2. The products obtained are added
  3. The sum is divided by 11 ( use sum % 11, not /, modulus, not division)
  4. If the remainder is less than 10, the remainder is the checksum digit, otherwise the checksum digit is zero
+------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| Position   |  1  |  2  |  3  |  4  |  5  |  6  |  7  |  8  |  9  |  10 |
+------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| Weight     |  x2 |  x4 |  x8 |  x5 | x10 |  x9 |  x7 |  x3 |  x6 |     |
+------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+

The weights are the powers of 2, modulo 11. (See also: Galois field applications)

Information leakage

The last digits of an EGN can reveal with reasonable accuracy the birthplace of a Bulgarian citizen, because of the long-lasting practice of assigning numbered sheets of paper to municipal ESGRAON divisions. Other divisions directly add the birth sequence number to the last 3 digits of their EKNM (a regional identifier) and possibly another 1 depending on the baby's sex. This practice is denied by ESGRAON officers, but is nevertheless used by civil authorities as a rule of thumb for checking the validity of an identity document.

Examples of valid EGN numbers

Misuse

In order to easily cross borders criminals have been known to change EGNs. There were 46 such cases detected in March 2005.

Using the EGN system for identification raised some privacy concerns, though they are officially considered personal information and are protected by law.

See also

External links

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