47 lines
1.3 KiB
HTML
47 lines
1.3 KiB
HTML
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<html>
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<body BGCOLOR="#00E0E0" link="#001fC0" vlink="#000080" text="#00000f">
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<h1><title> Hints to Choosing 'e' </title></h1>
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<h1> Hints to Choosing 'e' </h1>
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The 'e' value along with the Modulus 'n' forms the public key.
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<p>
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It is used to encode information by taking the data to encode 'm',
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to the power of 'e' and then applying the mod operator
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(remainder of division) between that result and the modulus value 'n'.
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<p>
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<h3>encoded = m<sup>e</sup>%n</h3>
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As it is part of the public key, (and therefore published)
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there is no point in it being a large number. Values like 3,5,7,11
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are all acceptable. The only restriction is that they should be co-prime
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to the phi value.
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<p>
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Some automatic algorithms for choosing 'e', simply start at 3, test
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for co-prime against phi, and on failure, increment 'e' by two and try again
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until they hit a co-prime combination.
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<p>
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If a non co-prime number is used, you may find it impossible
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to calculate the secret key in the next stage...
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<p>
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If 1 is chosen for 'e', it will be co-prime to any value of
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phi, but this will mean that the secret key will be 1 also, not very secure !
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<p>
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Hit the back button and try some values for 'e' until you have a co-prime
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value....
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<br>
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<br>
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<br>
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<center>
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<a href="javascript:history.back();">
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<img src=back.png align=center border=0> </a>
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</center>
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</body>
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</html>
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