Problem 45282. Cryptography with A Square Matrix : Decoding

Created by Mehmet OZC

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Previous Problem: <a href = "https://www.mathworks.com/matlabcentral/cody/problems/45279-cryptography-with-a-square-matrix-encoding">Cryptography with A Square Matrix : Encoding</a>Now decode a double vector to a (hopefully!) meaningful text.Inputs are encoded vector and key matrix.<pre> encodedVector = [1665 1624 1541 1549 1495 1501 486 510 534 1503 1552 1595 1192 747 836]</pre><pre> key = magic(3);</pre>inverse of key<pre> inverseKey = [0.147222222222222 -0.144444444444444 0.0638888888888889
 -0.0611111111111111 0.0222222222222222 0.105555555555556
 -0.0194444444444445 0.188888888888889 -0.102777777777778];</pre>Reshape encodedVector so it has the same number of rows with key<pre> reshapedVector = [1665 1549 486 1503 1192;
 1624 1495 510 1552 747;
 1541 1501 534 1595 836];</pre>Multiply inverseKey and reshapedVector, round it and reshape it;<pre> messageVector = [109 97 116 108 97 98 32 38 32 99 111 100 121 32 32];</pre>char equivalent of message vector is 'matlab & cody'

Previous Problem: <https://www.mathworks.com/matlabcentral/cody/problems/45279-cryptography-with-a-square-matrix-encoding Cryptography with A Square Matrix : Encoding>

Now decode a double vector to a (hopefully!) meaningful text.

Inputs are *encoded vector* and *key* matrix.

encodedVector = [1665 1624 1541 1549 1495 1501 486 510 534 1503 1552 1595 1192 747 836]

key = magic(3);

inverse of *key*

inverseKey = [0.147222222222222 -0.144444444444444 0.0638888888888889
               -0.0611111111111111 0.0222222222222222 0.105555555555556
               -0.0194444444444445 0.188888888888889 -0.102777777777778];

Reshape *encodedVector* so it has the same number of rows with *key*

reshapedVector = [1665 1549 486 1503 1192;
                     1624 1495 510 1552 747;
                     1541 1501 534 1595 836];

Multiply *inverseKey* and *reshapedVector*, round it and reshape it;

messageVector = [109 97 116 108 97 98 32 38 32 99 111 100 121 32 32];

char equivalent of message vector is 'matlab & cody'

Solve

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Last Solution submitted on May 02, 2022

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Solution 5986305

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1 Comment

Dyuman Joshi on 19 Jun 2021

Surprised my answer is the leading solution

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Problem 45282. Cryptography with A Square Matrix : Decoding

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