FA-72614 / Check-digit algorithms / Member archive

MRZ filler character is scored like a letter · case 04

Document numbers padded with "<" fail their check digit.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Machine-readable passport (TD3) second line, 44 characters of 0-9, A-Z and the filler "<" (else "malformed"). Check digits use weights 7,3,1 restarting per field, "<" = 0, A-Z = 10-35: document number [0:9] check [9]; birth date [13:19] check [19]; expiry [21:27] check [27]; optional data [28:42] check [42] (a "<" check is allowed only when the optional field is entirely filler); composite check [43] over [0:10]+[13:20]+[21:43]. Return five booleans.

Why this case matters

Border-control kiosks verify MRZ check digits to catch OCR misreads before a database query.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression ["HM87YWD225UTO1907195F3112216<<<<<<<<<<<<<<<0"]	`[true, true, true, true, false]`	`[true, true, true, true, true]`	Failed

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