Thank you for the quick reply, I will look into the R packages. For crashing R try this:
generator.zp=function(x,p) {a=1:(p-1); b=x^a%%p; if(all(b[1:(p-2)]!=1)&&(b[p-1]==1)){return(x, " Good ")} else{return(x, " No Good, try another integer ")} } This checks if element x is a generator of the group Z_p. If you try this function for p = 41 and x various increasing values eventually it will crash R. That is what I meant by random, at first I started x=2,3 so on, when I got to 8, R crashed. Now apparently I can get to 15. When I tried again I got to 20. Ionut Florescu Duncan Murdoch wrote: > On 1/30/2006 11:32 AM, Ionut Florescu 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. > > Could you keep a record of the random crashes, and see if you can make > any of them repeatable? R shouldn't crash. If you can find a > repeatable way to make it crash, then that's a bug that needs to be > fixed. (If it crashes at random it should still be fixed, but it's so > much harder to fix that it's unlikely to happen unless the cases are > ones that look likely to come up in normal situations.) > > >> >> 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). > > No, but there is at least one contributed package that does multiple > precision integer arithmetic. I can't remember the name of it right > now, but Google should be able to find it for you... > > Duncan Murdoch >> >> 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 > > ______________________________________________ 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