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    Password Hacking Guide by Passgener

    Version: 1.0 | Updated: 12/30/09 | Search Guide | Bookmark Guide

                             G.I. Joe: A Real American Hero
                          Password Hacking Guide by Passgener
                             Version 1.0 (29 December 2009)
                         Check GameFaqs.com for latest version!
    === Contents ==================================================================
     [1] Important! Read me first!
     [2] About this guide
     [3] Raw (unencoded) data format
     [4] Encoding a password
     [5] Example
     [6] Ready-Made Passwords!
     [7] Legal
    === [1] Important! Read me first! =============================================
    Section 6 of this guide contains a ready-made set of 'ultimate' passwords. I'm
    saying this up front since I don't want anyone to decide they aren't interested
    in this guide before they find out this information which is still probably
    useful to some people who wouldn't otherwise care.
    === [2] About this guide ======================================================
    The purpose of this guide is to explain the secrets behind the password system
    for the G.I. Joe NES game. I simply want this information to be known since
    there are certain individuals such as myself that might find it interesting.
    More generally, this simply allows you to create customized passwords for the
    game provided you have a basic understanding of binary numbers; if you don't
    then see section 6.
    This guide explains the format and encoding of the passwords in a straight
    forward but still firmly technical manner. When I originally decided to hack
    this system I thought that once I figured it out I could write a guide in a
    non-technical manner that would allow anyone to generate their own passwords.
    Once I figured out the system though I decided that certain aspects of it
    really required a basic understanding of binary numbers and so trying to
    explain it a non-technical manner would probably make it more convoluted than
    it really needed to be.
    As for the motivation for this guide, I've already mentioned that this
    information is of interest to individuals like me. By that I simply mean people
    who are interested in video games that have password systems. This game in
    particular is interesting to me because it was the first or one of the first
    games I ever played that had a password system and had always wanted to figure
    out how the passwords worked.
    Of course, back in grade school, when the game was new, I simply hadn't
    acquired the necessary skill to be able to decipher how they worked but now, in
    late 2009, I'm much smarter and cooler than I was back then. :) The mood just
    hit me one day and I thought it would be fun to give it a try again so I fired
    up the NES and the end result is this guide.
    === [3] Raw (unencoded) data format ===========================================
    In its raw form a G.I. Joe password consists of nine 4-bit values each one
    corresponding to one character of the password. Here's a bit map for the basic
    format (the left-most bit in each value is the most significant bit):
      aaaa bbcc ddee ffgg hhii jjkk llmm nnoo pppp
    Bits   Meaning
    aaaa   Mission number
      bb   Quest number
      cc   Unknown; probably unused
      dd   Duke's stamina
      ee   Duke's weapon level
      ff   Blizzard's additional stamina
      gg   Blizzard's weapon level
      hh   Snake Eye's additional stamina
      ii   Snake Eye's weapon level
      jj   Captain Grid-Iron's additional stamina
      kk   Captain Grid-Iron's weapon level
      ll   Rock & Roll's additional stamina
      mm   Rock & Roll's weapon level
      nn   General Hawk's additional stamina
      oo   General Hawk's weapon level
    pppp   checksum value
    Each group of the same letter in the map represents a single 2-bit or 4-bit
    The mission number wastes some space since only six values are used in a full
    4-bit value. If the password contains any value other than those listed below
    then the game will reject the password even if it is otherwise valid:
    Bits   Meaning
    0001   Mission 1
    0010   Mission 2
    0011   Mission 3
    0100   Mission 4
    0101   Mission 5
    0110   Mission 6
    The quest number is the upper two bits of the second 4 bit value. If the
    password contains any value other than those listed below then the game will
    reject the password even if it is otherwise valid:
    Bits   Meaning
      00   First quest
      01   Second quest
      10   Third quest
    The lower two bits of the second 4-bit value appear to be unused but I can't be
    absolutely sure. The game will accept any of the four possible values and they
    appear to have no effect.
    The third, fourth, fifth, sixth, seventh and eight 4-bit values contain the
    weapon and stamina data for Duke, Blizzard, Snake Eyes, Captain Grid-Iron, Rock
    & Roll and General Hawk, respectively.
    The upper four two bits are the additional stamina. This 2-bit value just gets
    added to the base stamina for the character to get the total stamina. Note that
    the character selection screen always shows the base stamina regardless of the
    modifier from the password.
    The lower two bits are the weapon level for the character:
    Bits   Meaning
      00   Level 1A
      01   Level 2A
      10   Level 3A
      11   MAX
    Make note of the fact that there is a slot in the password for General Hawk.
    This is interesting since you can only use General Hawk in Mission 6 and his
    stats do not carry over between quests. To me this suggests that, originally,
    the developers were planning on making him available on other stages but
    decided later not to. I have no proof of this but can't imagine why else there
    would be data for him in the password. I don't believe the game will ever give
    you a password were Hawk has anything other than base stats but it will happily
    accept a password where his stats are higher.
    The last value is a check digit and how to calculate it is covered in the next
    === [4] Encoding a password ===================================================
    Encoding a password from the raw data requires several steps. First layout your
    raw data in nine 4-bit values as described in section 3.
    Next add the position number of each value to the value itself starting from
    the left going to the right where the first value is considered position 0.
    Skip the checksum value at the end (position 8) and leave it as value zero. If
    the resulting value is more than 4-bits (i.e. greater than 15) then simply
    throw out the upper bits and keep only the lower four (e.g. 2 + 15 = 1). For
    example, if you started out with all 9 nine values being zero and performed
    this step then you'd end up with these nine values:
      0000 0001 0010 0011 0100 0101 0110 0111 0000
    To compute the checksum, first set the checksum value (position 8) to zero.
    Then process each value in order as follows starting from the left and moving
    right. For each value, add the value to the checksum (position 8) and then
    rotate the bits of the checksum left once. Rotating the bits left means
    basically to shift all the bits in the value up in value but the most
    significant bit loops around and becomes the least significant bit. If that
    doesn't make sense then just use this map:
      abcd -> bcda
    The last step is just to convert the 4-bit numbers to the characters of the
    password. This is complicated by the fact that a different set of characters is
    used depending on the value of the two lower bits of the checksum. Don't change
    the value of the checksum at this point but just look at the two lower bits.
    Next, run through each of the first eight values (ignore the checksum for now)
    and use the appropriate table to convert each value to a character.
    |           |       Checksum value      |
    | Raw Value | xx00 | xx01 | xx10 | xx11 |
    | 0000      |   3  |   V  |   H  |   Z  |
    | 0001      |   S  |   Z  |   3  |   R  |
    | 0010      |   P  |   D  |   6  |   B  |
    | 0011      |   N  |   3  |   9  |   J  |
    | 0100      |   5  |   9  |   N  |   0  |
    | 0101      |   X  |   N  |   5  |   V  |
    | 0110      |   G  |   5  |   X  |   D  |
    | 0111      |   Z  |   X  |   G  |   8  |
    | 1000      |   R  |   S  |   Z  |   5  |
    | 1001      |   D  |   G  |   R  |   H  |
    | 1010      |   B  |   8  |   D  |   3  |
    | 1011      |   2  |   B  |   V  |   S  |
    | 1100      |   0  |   2  |   8  |   9  |
    | 1101      |   H  |   R  |   0  |   N  |
    | 1110      |   V  |   0  |   B  |   X  |
    | 1111      |   8  |   Q  |   2  |   G  |
    Finally, use this table to convert the checksum value to a character and the
    password is completely encoded and ready to use.
    Checksum   Character
    0000       0
    0001       1
    0010       2
    0011       3
    0100       4
    0101       5
    0110       6
    0111       7
    1000       8
    1001       9
    1010       B
    1011       C
    1100       D
    1101       F
    1110       G
    1111       H
    === [5] Example ===============================================================
    As an example, let's say we want to start playing from Mission 3 on the second
    quest with Snake Eyes maxed out. First we'll layout this raw data:
      0011 0100 0000 0000 1111 0000 0000 0000 0000
    Next, we'll run through and add the position number of each value to the value:
      0011 0101 0010 0011 0011 0101 0110 0111 0000
    Now that that's done we can compute the checksum (remember to add then rotate
    each time):
      0011 0101 0010 0011 0011 0101 0110 0111 1000
    Then convert each of the first eight values to characters using the first table
    from section 4:
      N    X    P    N    N    X    G    Z    1000
    Finally, use the second table from section 4 to convert the checksum value to a
    character and we have a complete password:
    === [6] Ready-Made Passwords! =================================================
    I know there are a few people who will find this guide interesting but I figure
    most people just want passwords with max stats and really don't care about or
    want to actually encode the passwords themselves. To that end, this section
    lists "ultimate" passwords for each mission and quest with all the character
    stats set to their maximums.
    Quest   Mission   Password
     1       1        RRRBJ0VD7
     1       2        PSSPN5XG0
     1       3        3ZZD39N55
     1       4        N3369N5XB
     1       5        NZZD39N59
     1       6        X3369N5XG
     2       1        ZNZD39N55
     2       2        65369N5XB
     2       3        3NZD39N59
     2       4        N5369N5XG
     2       5        VVRBJ0VD3
     2       6        X5369N5X6
     3       1        ZGZD39N59
     3       2        6R369N5XG
     3       3        JHRBJ0VD3
     3       4        NR369N5X6
     3       5        VHRBJ0VD7
     3       6        GDSPN5XG0
    It also occurs to me that some people might want the opposite extreme where all
    the characters have basic stats so here are those passwords as well:
    Quest   Mission   Password
     1       1        RRBJ0VD8C
     1       2        6369N5XG6
     1       3        3ZD39N5XF
     1       4        5SPN5XGZ8
     1       5        5369N5XGG
     1       6        DRBJ0VD8H
     2       1        ZND39N5XF
     2       2        PXPN5XGZ8
     2       3        9569N5XGG
     2       4        0VBJ0VD8H
     2       5        NND39N5X9
     2       6        GXPN5XGZD
     3       1        3R69N5XGG
     3       2        BHBJ0VD8H
     3       3        3GD39N5X9
     3       4        5DPN5XGZD
     3       5        VHBJ0VD8C
     3       6        XR69N5XG6
    If you want any others then you are on your own.
    === [7] Legal =================================================================
    I, the author of this document, make no claim of copyright or responsibility to
    the content therein. You are free to use and distribute it as you see fit and
    do so entirely at your own risk.

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