Generate Random Finnish, Norwegian and Swedish Personal Identification Numbers

generate_pin.rb

# NOTE: Gender is something these countries use to calculate the serial/individual number(making them even or odd)
# It is not taken into consideration in this snippet but the generated numbers are still valid
require 'date'

age = 21 # Whatever you want it to be

# Randomize month and day equal to, or lower, than the current month
# to make sure the generated birth month and day has occurred in <current_year>
t = Time.new
year = t.year - age
month = t.month - Random.rand(1..t.month) + 1
day = t.day - Random.rand(1..t.day) + 1

# Make sure we don't end up with Feb 29th on a non-leap year(or other invalid dates)
# This will happen extremely rarely, but better safe than sorry
while not Date.valid_date?(year, month, day)
  day = t.day - Random.rand(1..t.day) + 1
end

birthdate = Date.new(year, month, day)

# ================================
# Generate Finnish Personal Number
# ================================
date = birthdate.strftime('%d%m%y')
individual_number = format('%03d', 2 + rand(899)) # 002-899

# The checksum is calculated as the remainder of the date + individual number divided by 31
# If the remainder is > 9 then the checksum is grabbed from a given character string with the remainder as index
remainder = "#{date}#{individual_number}".to_i % 31
if remainder < 10
  fi_personal_number = "#{date}#{individual_number}#{remainder}"
else
  char_string = '0123456789ABCDEFHJKLMNPRSTUVWXY'
  checksum = char_string[remainder]

  fi_personal_number = "#{date}#{individual_number}#{checksum}"
end

puts "Finnish: #{fi_personal_number}"

# ==================================
# Generate Norwegian Personal Number
# ==================================
def weigh_numbers(number, weight)
  weighted = 0
  number.split('').each_with_index do |digit, indx|
    weighted += (digit.to_i * weight[indx].to_i)
  end

  weighted
end

date = birthdate.strftime('%d%m%y')
checksum1 = 10
checksum2 = 10

while checksum1 == 10 || checksum2 > 9
  if year >= 1900 && year <= 1999
    individual_number = format('%03d', rand(499)) # 000-499
  elsif year >= 2000 && year <= 2039 # 2039 is the current limit
    individual_number = format('%03d', 500 + rand(999)) # 500-999
  end

  # The nine digits we have so far are weighted to calculate the 10th digit
  weighted = weigh_numbers("#{date}#{individual_number}", '376189452')
  checksum1 = 11 - (weighted % 11)
  checksum1 = 0 if checksum1 == 11

  # Then, the now ten digits we have are weighted to calculate the 11th digit
  weighted = weigh_numbers("#{date}#{individual_number}#{checksum1}", '5432765432')
  checksum2 = 11 - (weighted % 11)
end

puts "Norwegian: #{date}#{individual_number}#{checksum1}#{checksum2}"

# ================================
# Generate Swedish Personal Number
# ================================
date = birthdate.strftime('%y%m%d') # If you want the 4-digit year you'll have to convert it after the calculactions
serial = format('%03d', 1 + rand(999)) # 001-999

# To calculate the checksum we start with multiplying every other number with 2
digits = []
"#{date}#{serial}".split('').each_with_index do |number, indx|
  product = number.to_i * (2 - indx % 2)
  # "a two digit product, such as 16, would be converted to 1 + 6"
  product = product.to_s[0].to_i + product.to_s[1].to_i if product.to_s.length == 2
  digits << product
end

# Add all products together into one sum
sum = digits.inject(0) { |prv, nxt| prv + nxt }
# Subtract the last digit in the sum from 10 to get the checksum
# If the last digit is 0, the checksum is automatically 0
checksum = 10 - sum % 10
checksum = 0 if checksum == 10

puts "Swedish: #{date}#{serial}#{checksum}"