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Old 2004-04-23, 01:33   #1
dsouza123
 
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Sep 2002

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Default 5dpf, 5 digits from the end partial factors

Rather than fully factoring a RSA number,
factor the first and last 5 digits of the two factors.

For example RSA-576 (174 digits)
18819881292060796383869723946165043980716356
33794173827007633564229888597152346654853190
60606504743045317388011303396716199692321205
734031879550656996221305168759307650257059

The two factors (both 87 digits) are
39807508642406493739712550055038649119906436
2342526708406385189575946388957261768583317

47277214610743530253622307197304822463291469
5302097116459852171130520711256363590397527

so the 5dpf, 5 digits from the end partial factors, are

39807r and r83317
47277s and s97527

r and s are used to both match the parts and indicate the ends.

Here is RSA-640 (193 digits)
310741824049004372135075003588856793003
734602284272754572016194882320644051808
150455634682967172328678243791627283803
341547107310850191954852900733772482278
3525742386454014691736602477652346609

Each of the two full factors will be very close to half the digits of the RSA-640 number.

What are the values for any/all of the four 5dpf ?
Also the reasoning behind the choice(s).
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