How the number is built and checked
An EMŠO has thirteen digits: day and month of birth, the last three digits of the year (932 for 1932), a two-digit register code (50), a three-digit serial — 000–499 for men, 500–999 for women — and a check digit. The interior ministry, which keeps the Central Population Register, assigns it. [1]
The check digit: multiply the first twelve digits by 7 6 5 4 3 2 7 6 5 4 3 2, add, divide by 11 and subtract the remainder from 11. A remainder of 0 gives 0. A remainder of 1 would give 10, which is not a digit, so that serial is skipped when numbers are assigned. [1]
The regulation works it through on a made-up number, 2902932505526, which it says was never assigned and never will be (a woman born on 29 February 1932): 14 + 54 + 0 + 8 + 27 + 6 + 14 + 30 + 0 + 20 + 15 + 4 = 192, 192 mod 11 = 5, and 11 − 5 = 6. [1]
nullcipher checks the date (9xx years as the 1900s, 0xx as the 2000s), rejects remainder 1 and compares the check digit; it does not require the register code to be 50. It masks the number only when EMŠO, EMSO or enotna matična številka občana stands within 40 characters before it.
How nullcipher recognises it
Thirteen digits: DDMM and a three-digit year (9xx for the 1900s, 0xx for the 2000s) forming a real date, a two-digit register code, a three-digit serial (000–499 men, 500–999 women) and the check digit: the first twelve digits times 7 6 5 4 3 2 7 6 5 4 3 2, summed; 11 minus the sum mod 11, with remainder 0 giving 0 and remainder 1 never issued. Masked with a context word — EMŠO, EMSO, enotna matična številka občana — within 40 characters before it.
This is the rule text of the “Slovenian EMŠO” detector in the masking engine, copied from the engine when this page was built. Detectors run in a fixed order and, where two overlap, the earlier one wins.
Example (fake)
EMŠO 2902932505526nullcipher replaces it with [EMSO_1]. This is the made-up example from the government regulation itself, which states it was never assigned and never will be.
Why it matters in an AI chat
An EMŠO gives away the exact date of birth and the sex, so next to a masked name it still points at one person.
Masked, the AI sees [EMSO_1] and can still help with the rest of the text.
If it already leaked
- If you suspect it has been misused, report the offence to the police: at a police station, on 113, or online with the police's e-naznanilo kaznivega dejanja (electronic crime report), which is handled the same way as a call to 113. [2]
- If it only went into an AI chat and there is no sign of misuse, delete the conversation — how, for each major assistant, is on the page listing every type. The EMŠO itself does not change.
Sources
- Uredba o načinu določanja osebne identifikacijske številke, Uradni list RS 8/1999, členi 3–4 in Priloga 1 — PISRS — checked 2026-10-03.
- E-storitve: E-naznanilo kaznivega dejanja — Policija — checked 2026-10-03.
Open the full masking tool to mask a whole log, .env file or e-mail — every type at once — and restore the values in the AI's answer. Or see all 242 detectors, with a page for 59 secret types, and how to delete a chat you already sent.