Results 1 to 2 of 2

Math Help - matrix message decoding

  1. #1
    Junior Member
    Joined
    Mar 2009
    Posts
    31

    matrix message decoding

    How do I set this up and how do I do the calculations?




    The message: 39 57 7 10 11 11 36 44 5 5 33 48 14 19 19 19 was encoded with matrix A.



    A =| 1 2 |
    .....| 1 3 |


    | 1 2 | 39 57 7 10 11 11 36 44

    | 1 3 | 5 5 33 14 19 19 19 19


    or


    | 1 2 | 39 7 11 36 5 33 14 19
    | 1 3 | 57 10 11 44 5 48 19 19


    (1) / ( (1)(3) - (-1)(-2) )


    -1 * | 3 -1 |
    .......| -2 1 |

    | -3 1 |
    | 2 -1 |

    and then I'm suppose to multiply this by the message. But how is this done?

    -3(39) = -117 ?
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    May 2010
    Posts
    1,030
    Thanks
    28
    Google says: http://mdm4u1.wetpaint.com/page/Enco...using+matrices


    you can break the message into a series of 2x2 matrices and multiple each by the inverse of the coding matrix.

    This means you need to know how your message string is supposed to be broken up into 2x2 elements. Presumably your course teacher or the question will have told you the notation for this (ie, wheter each pair of numbers in the message corresponds to a row or a column).


    I cant follow your working, but if
    | -3 1 |
    | 2 -1 |
    is supposed to be the inverse of the coding matrix it doesn't appear to be correct. see link
    http://www.wolframalpha.com/input/?i...}%2C+{1%2C+3}}
    Last edited by SpringFan25; April 15th 2011 at 06:43 AM.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Coset Decoding
    Posted in the Number Theory Forum
    Replies: 0
    Last Post: May 25th 2010, 04:01 PM
  2. Decoding a message
    Posted in the Discrete Math Forum
    Replies: 1
    Last Post: November 9th 2009, 02:01 PM
  3. encoding and decoding help
    Posted in the Number Theory Forum
    Replies: 4
    Last Post: June 7th 2008, 09:44 AM
  4. decoding
    Posted in the Discrete Math Forum
    Replies: 1
    Last Post: February 23rd 2008, 12:51 PM
  5. Decoding bits set
    Posted in the Math Software Forum
    Replies: 0
    Last Post: December 29th 2007, 11:16 PM

Search Tags


/mathhelpforum @mathhelpforum