DBAKey constructor
Constructs DBAKey using passport number mrtdNumber,
passport owner's dateOfBirth and passport dateOfExpiry.
Implementation
DBAKey(String mrtdNumber, DateTime dateOfBirth, DateTime dateOfExpiry,
{bool paceMode = false}) {
_mrtdNum = mrtdNumber;
_dob = dateOfBirth.formatYYMMDD();
_doe = dateOfExpiry.formatYYMMDD();
seedLen = paceMode ? SEED_LEN_PACE : SEED_LEN_BAC;
}