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ISO mDL & Core Data Format

Today, our driver’s licenses are scannable physical cards we carry around in our wallets. Conversely, in order for cryptographically signed ID documents to be machine-readable for various use cases, there needs to be a cross-industry and cross-jurisdiction approach for standardizing data formats. The Mobile Driver’s License standard (mDL, ISO 18013-5) is required by TSA for airport security with implementations by several states underway already, including California, Maryland, Arizona, and Colorado. We previously walked through the standard and its components in, but we'll briefly explain the core data format here.
Imagine a spreadsheet where all the records are stored for licensed drivers in a given state. The data are not stored in a spreadsheet but rather in a data array, similar to a spreadsheet but compact enough to fit on a device. This “spreadsheet” would require a consistent naming convention for each of the columns in that spreadsheet to ensure that if someone from another state or agency was reading the spreadsheet, they knew exactly what data attributes the specific columns were referencing. For example, consistent data formats would require universally using “birth_date” as the identifier for a person’s date of birth, not “dob,” or “date_of_birth,” and so on, as outlined in the ISO/IEC 18013-5 specification.
The following identifiers, as encoded below, are mandatory for mobile driver's licenses to adhere to the mDL ISO standard.
The last name, or surname, of the mDL holder
The first name(s) of the mDL holder
The day, month, and year on which the mDL holder was born
The date when the mDL was issued
The date when the mDL expires
The alpha-2 country code of the issuing authority's country or territory
The issuing authority name
The number assigned or calculated by the issuing authority
A reproduction of the mDL holder's portrait
The driving privileges of the mDL holder
In addition to the fields outlined above, AAMVA furthers the mandatory data field requirements with the following additions changed from "Optional" to "Mandatory."
The mDL holder’s height in centimeters
The mDL holder’s sex using values as defined in ISO/IEC 5218.
The color of the mDL holder's eyes. Values include: “black”, “blue”, “brown”, “dichromatic”, “grey”, “green”, “hazel”, “maroon”, “pink”, “unknown”.
The age of the mDL holder in years
A true/false statement for whether the holder is over a certain age.
Next, we will explore the underlying technology utilized to ensure security and verifiable authenticity for digital credentials, like mobile driver’s licenses.