Hacker News Reader

Mine is a friend's birthday. Not a lover/ex, not even that close of a friend. So people that know me would never guess it, and for a stranger, it is just random number.

It also have the advantage of not having to save it in a password manager, since I have it on my calender (with a lot of other birthdays saved).

View on HN

It's definitely not random. For example there is very little chance it contains a 4, and a very good chance it contains a 1.

Exactly. If you're going to do a birthday-based PIN, it's important to consider that the 10s digit of month and year have heavily reduced search-space.

4-digit Birthday-pins are probably good as long as they're not your birthday or that of your kids, and you do the last 2 digits of year, last digit of month, last digit of day, go capture as much of the entropy from the date as possible.

People under 100 only have 36.500 different birthdays.

You've left out 25 leap days.

On a side note, I remember back in 2004, a colleague born on Feb 29th, 1984 was unable to enter the U.S. H1B renewal website because someone forgot about leap years in their date validation logic.

Reply on news.ycombinator.com