Which data masking function to use to mask bank account numbers?

An IBAN number is composed of several elements. Here is the terminology used for the data masking functions:

Black: Country code
Coral: Check digits
Light blue: Bank/branch code
Dark blue: Account number
Gray: National check digits. Their position in the IBAN number depends on the country.
Some countries do not use national check digits.

To mask bank account numbers by other bank account numbers, you can use different data masking functions. To help you decide which function is the most suitable, the following table sums them up:

Function		Generate account number and keep original country	Mask bank code and account number and keep original country	Mask account number and keep original country and bank code
Behavior		Input valid: Generates bank account numbers conform to the corresponding country Input not valid: Generates French IBAN numbers	Uses the format-preserving encryption Input valid: Masks the bank account number Input not valid: Sends the input data to the "Invalid" flow or returns `null` in the main flow	Uses the format-preserving encryption Input valid: Masks the bank account number and keeps the bank/branch code Input not valid: Sends the input data to the "Invalid" flow or returns `null` in the main flow
Behavior		* To determine if an input is valid, the functions verify different criteria.
Input validation ¹	Validate country code
	Validate format
	Validate IBAN check digits
	Validate national check digits		²	²
	Validate bank/branch code
Output validity ¹	Valid country code
	Valid format
	Valid IBAN check digits
	Valid national check digits	²	²	²
	Valid bank/branch code			³
¹ According to the country code ² For some countries (see the list below). For other countries, the national check digits may not be valid. ³ If the input bank/branch code is valid.

Which national check digits are handled?

The national check digits of the following countries are handled:

Belgium
Bosnia
Croatia
Czech Republic
Estonia
France
Hungary
Italy
Mauritania
Monaco
Montenegro
Norway
Portugal
San Marino
Serbia
Slovakia
Slovenia
Spain
Timor-Leste
Tunisia

National check digits from other countries are supported but not handled. This means that the functions cannot determine whether the national check digits are conform to the corresponding country or not.

Some countries do not use national check digits.

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