User Tag List

Results 1 to 1 of 1

Thread: The Hill Cipher: A practical application of matrix and modulus mathematics2051 days old

  1. #1
    Established Member
    卐 Generalissimo 卐 DrDawud's Avatar
    Last Online
    2018-03-05 @ 03:13
    Join Date
    2009-12-27
    Posts
    382
    Location
    Asia-Pacific
    Gender
    Race
    East Asian
    Phenotype
    Sinid
    Ethnicity
    Han
    Politics
    Reactionary
    Religion
    al-Islam
    China Taiwan Islamic Conference Antarctica Hong Kong

    Default The Hill Cipher: A practical application of matrix and modulus mathematics

    The Hill Cipher was invented by Lester S. Hill in 1929 and was the first polygraphic cipher in which it was practical to operate on more than three symbols at once.

    In the Hill Cipher, you start with a string, for instance "OMNIA GALLIA IN TRES PARTES DIVISO EST". Each letter in the string can be mapped uniquely to a numerical value from 0 to k, providing that k is prime, and that you have enough characters such that there is always a 1-1 correspondence. A common arrangement is A=0, B=1, C=2, etc., but it is possible to permute this mapping to anything one wishes.

    For the sake of simplicity, we will use k=29 (the smallest possible prime using the standard English alphabet), and the arrangement that A=0, B=1...Z=26, along with the extra characters 27 = "space" 28 = ? and 29 = !. We now convert the letters into their numeric values. This is represented as a vector, which we will call 'P' for Plaintext

    P = [14, 12, 13, 8, 0, 26, 6, 0, 11, 11, 8, 0, 26, 8, 13, 26, 19, 17, 4, 18, 26, 15, 0, 17, 19, 4, 18, 26, 3, 8, 21, 8, 18, 14, 26, 4, 18, 19]

    The next step is to choose a n-by-n matrix of positive, non-zero integers. In theory, any number could be used, but in practice values from 1-k are used. The number 0 tends to be avoided because multiplying by 0 often results in losing information.

    For this, we will choose the matrix:

    E = [28 7 16
    3 13 5
    2 9 19]

    Since P can’t be multiplied by C directly, P should be split up into i blocks, P1 to Pi, such that block contains n elements, arranged in a column. So, P1 = [14, 12, 13]T, P2 = [8, 0, 26]T, etc. until all the numbers are exhausted. If the last two set, Pi, has less than n elements, they can be "filled" in using random numbers.

    After this, the next step is to multiply each P column vector by E modulus n, to get the ciphertext for that block, C.

    (E*Pi) mod n = Ci

    It goes without saying that Ci is likewise a column matrix with n elements. You do this until all P column vectors have been encrypted into C, then you use your original mapping (A=0, B=1...Z=26) to get a ciphertext. If you do this, you should get:

    RCGSOHZPSQVHFSZBH?DEQZOFHZKGPBEZVHH!XES,

    Which is quite different from what we had originally. Note that the pair "LL" in GALLIA becomes 'SQ'. So that in the cipher text, there is not a one-to-one correspondence as there are in monoalphabetic ciphers.

    The Drawback to this method is that, because it is computed by simple matrix multiplication, and the matrix does not change, it is completely linear. With modern computing technology, it is very easy to solve this given a sufficient plaintext/ciphertext pair (mathematically, it can be solved in as few as n2 (in this case 81) pairs (i.e. a message with 81 characters).

    Nonetheless, it can still be used as a primary step in other encryption methods.
    If you're ever in any trouble, just give me the signal and I'll send you one of my 357 Pain Pills.

  2. The Following 2 Users Say Thank You to DrDawud For This Useful Post:

    Day Tripper (2014-01-11), Xochi (2014-08-02)

  3. # ADS
    Advertisement bot
    Join Date
    2013-03-24
    Location
    ForumBiodiversity.com
    Posts
    All threads
       
     

Similar Threads

  1. my online Cognitive Test application
    By MartinK84 in forum Behavioural Neuroscience
    Replies: 0
    Last Post: 2012-02-14, 19:56
  2. Phenotype application
    By Splicer in forum Genetic DNA Companies
    Replies: 3
    Last Post: 2011-10-02, 10:33
  3. SNP Map application
    By Red Rover in forum Genetic DNA Companies
    Replies: 6
    Last Post: 2011-06-24, 20:25
  4. Infractions: Inconsistent application
    By Humata in forum Help & Suggestions
    Replies: 8
    Last Post: 2010-08-21, 15:46
  5. Y-DNA Correlation Matrix Results For Select Populations
    By Humanist in forum y-DNA Haplogroups
    Replies: 21
    Last Post: 2010-08-16, 16:08

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
<