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
You have reached the maximum value that can be stored accurately in a
floating point number. That is what the error message is telling you. I
get 21 warnings and this says that at 8^20 I am now truncating digits in the
variable. You only have about 54 bits in the floating point number and you
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
R is probably not the best tool for handling large integers...
AFAIK Python has the interesting feature of not only having a `long' integer
type (that can store arbitrarily large integers), but can convert a regular
4-byte int to the `long' type when necessary. Perhaps that would be a
better
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
On 1/30/2006 1:39 PM, Ionut Florescu wrote:
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 )}
}
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 64.004 (not exactly an
integer); roundoff errors are apparent in the other values.
8^(1:20)
This is a double protection error in real_binary. See the R-devel list
for the details. Now fixed.
On Mon, 30 Jan 2006, Ionut Florescu wrote:
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;
Thank you, I didn't notice that. I may have to come up with my own power
function as well, slower but precise.
jim holtman wrote:
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
jim holtman [EMAIL PROTECTED] writes:
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 64.004 (not exactly an
integer); roundoff errors
Actually it does that in my 2.2.1 version as well:
options(digits=20)
8^(1:20)
[1] 8.e+00 6.4004e+01 5.1201e+02
[4] 4.0961e+03 3.27680002e+04 2.62144002e+05
[7] 2.09715199e+06 1.67772159e+07
Ionut Florescu [EMAIL PROTECTED] writes:
Actually it does that in my 2.2.1 version as well:
options(digits=20)
8^(1:20)
[1] 8.e+00 6.4004e+01 5.1201e+02
[4] 4.0961e+03 3.27680002e+04 2.62144002e+05
[7]
On Mon, 30 Jan 2006, Peter Dalgaard wrote:
Ionut Florescu [EMAIL PROTECTED] writes:
Actually it does that in my 2.2.1 version as well:
options(digits=20)
8^(1:20)
[1] 8.e+00 6.4004e+01 5.1201e+02
[4] 4.0961e+03 3.27680002e+04
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