Viewing Single Post From: My New Cipher

Viewing Single Post From: My New Cipher
jdege	Apr 16 2008, 11:59 AM
Elite member Posts: 263 Group: Admin Member #246 Joined: December 7, 2006	Paarth Dave Apr 15 2008, 10:24 PM What do you mean by vectors and matrix multiplication? It would be very appreciable if you show this method by an example. A matrix is a two-dimensional array of numbers, a vector is a one-dimensional sequence of numbers. The multiplication of a vector by a matrix yields another vector. Suppose our plaintext is "SEND HELP", and our key is the 2x2 matrix: Code: `[ 3 5 ] [ 7 11 ]` We take the plaintext two letters at a time, treating each letter as an integer mod-26: Code: `"S" = 18, E" = 4 : [ 18 ] [ 4 ]` We multiply the matrix and the vector: Code: `[ 3 5 ] * [ 18 ] = [ 3 * 18 + 5 * 4 ] = [ 2 + 20 ] = [ 22 ] [ 7 11 ] [ 4 ] [ 7 * 18 + 11 * 4 ] [ 22 + 18 ] [ 14 ]` And since 22 = "W" and 14 = "O", we thus encode "SE" as "WO". We do the same process for the remaining pairs of plaintext letters, adding a random padding character at the end if we're one short. To decrypt, we multiply by a matrix that is the inverse of the one we used to encrypt. Not all matrices can be inverted - we can only use invertible matrices as keys.
	When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

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