Elizabeth Swann Traditional Open Identification Number

The Elizabeth Swann Traditional Open Identification Number (abbreviated ESTOIN and can also be written as estoin), is a unique, alphanumeric code that identifies many of the gamers that are fans of Nintendo, Kairosoft, King.com or Pokemon games. This identifier is used to make sure that the specified gamer can handle the system correctly to prevent it from being damaged to Elizabeth Swann's structure.

In early 2014, Isabelle and Elizabeth Swann made an announcement that a new system Elizabeth Swann Traditional Open Identification Number will go into effect later this year, but in June 2014, it was pushed back to early 2015.

On the 31 December 2014, for the New Year, the first ESTOIN was issued to Anamorphose (3DS friend code 4597-0360-8077). By 2 January 2015, the identification system was rolled out to all users.

This identification system is run by Elizabeth Swann and Isabelle.

Structure
The ESTOIN contains 19 alphanumeric characters. This is because 19 is a prime number and is better suited for the length of ESTOIN.

Characters 1 and 2 indicate where the user lives (AX: Asia, EU: Europe, AU: Australia, MX: Mexico). For users living in the USA or Canada, the abbreviation for the state in USA or Canada where the user lives is used instead. Characters 3 and 4 are taken from the last two digits of the registration year (for example, 2014 = 14, 2015 = 15, etc.) Characters 5 and 6 are reserved as '00'. Characters 7 through 17 are the random alphanumeric string in order to distinguish the user from other users with the same location and registration year. The last two characters (18 and 19) are check digits and are generated by separate techniques: Letters are converted to numbers based on their ordinal position in the alphabet, starting with A equal to 10.
 * The 18th character is calculated using the "MOD 11 987-654-32" technique (every digit is multiplied by weights of 9, 8, 7, 6, 5, 4, 3, 2, 9, 8, 7, 6, 5, 4, 3, 2, 9, then the sum is divided by 11: if the remainder is 10, the 18th character is 0).
 * The 19th character is calculated using the "Modulus 10 Double Add Double" technique based on the Luhn algorithm (every second digit is multiplied by two).

The two check digits catch single-digit errors, twin errors and most transposition errors, but it would not catch some of the transposition errors and some of the twin errors. This leads to a check digit flaw. To fix this, using the "ISO/IEC 7064 MOD 97-10" technique would have been better rather than two separate algorithms.