From: jim holtman <jholtman_at_gmail.com>

Date: Tue 31 Jan 2006 - 05:59:28 EST

[5] 3.2768000000000002e+04 2.6214400000000002e+05 2.0971519999999999e+06 1.6777215999999999e+07

[9] 1.3421772800000000e+08 1.0737418240000001e+09 8.5899345920000005e+09 6.8719476736000003e+10

[13] 5.4975581388799997e+11 4.3980465111039999e+12 3.5184372088832001e+13 2.8147497671065600e+14

[17] 2.2517998136852482e+15 1.8014398509481984e+16 1.4411518807585588e+17 1.1529215046068471e+18

*>
*

Date: Tue 31 Jan 2006 - 05:59:28 EST

The other thing that you have to be aware of is that 8^n is not 8 multiplied by itself n times. You are probably using logs to compute this. Here is a sample of 8^(1:20). The value of 8^2 is 64.000000000000004 (not exactly an integer); roundoff errors are apparent in the other values.

*> 8^(1:20)
*

[1] 8.0000000000000000e+00 6.4000000000000004e+01 5.1200000000000001e+024.0960000000000001e+03

[5] 3.2768000000000002e+04 2.6214400000000002e+05 2.0971519999999999e+06 1.6777215999999999e+07

[9] 1.3421772800000000e+08 1.0737418240000001e+09 8.5899345920000005e+09 6.8719476736000003e+10

[13] 5.4975581388799997e+11 4.3980465111039999e+12 3.5184372088832001e+13 2.8147497671065600e+14

[17] 2.2517998136852482e+15 1.8014398509481984e+16 1.4411518807585588e+17 1.1529215046068471e+18

On 1/30/06, Ionut Florescu <ifloresc@stevens.edu> wrote:

*>
*

> I am a statistician and I come up to an interesting problem in

*> cryptography. I would like to use R since there are some statistical
**> procedures that I need to use.
**> However, I run into a problem when using the modulus operator %%.
**>
**> I am using R 2.2.1 and when I calculate modulus for large numbers (that
**> I need with my problem) R gives me warnings. For instance if one does:
**> a=1:40;
**> 8^a %% 41
**> one obtains zeros which is not possible since 8 to any power is not a
**> multiple of 41.
**> In addition when working with numbers larger that this and with the mod
**> operator R crashes randomly.
**>
**> I believe this is because R stores large integers as real numbers thus
**> there may be lack of accuracy when applying the modulus operator and
**> converting back to integers.
**>
**> So my question is this: Is it possible to increase the size of memory
**> used for storing integers? Say from 32 bits to 512 bits (Typical size of
**> integers in cryptography).
**>
**> Thank you, any help would be greatly appreciated.
**> Ionut Florescu
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide!
**> http://www.R-project.org/posting-guide.html
**>
*

-- Jim Holtman Cincinnati, OH +1 513 247 0281 What the problem you are trying to solve? [[alternative HTML version deleted]] ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.htmlReceived on Tue Jan 31 06:25:58 2006

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