biginteger on Objective-c

Question

Can anyone provide code for a biginteger implementation in objective-c that provides a PowMod function ?

Answer 1

The closest builtin class in the Cocoa libraries is NSDecimalNumber which provides base-10 arithmetic (and so can handle integer-only arithmetic) for the range mantissa x 10^exponent where mantissa is a 38-bit float and exponent is -128 to 128. If that covers the range you need, there are multiplication and power methods. Otherwise, since Objective-C is a superset of C, any C implementation of bigint that you can find will suffice.

Answer 2

As plain C library, openssl's BN should be able to do it.

BN_mod_exp() computes a to the p-th power modulo m (r=a^p % m). This function uses less time and space than BN_exp().

Answer 3

I rolled my own wrapper around GMP once, long ago. I've never used any third party BigNum ObjC librariers before, but I had these bookmarked: RSMath, which uses the OpenSSL bignum functions, and MPInteger, which uses GMP.

Answer 4

Thanks to all for the response .

HI Johne

regarding the RSNumer in RSmath can i use the below method for poWMod? function ?

toThePowerOf:(RSNumber *) otherNumber mod:

How do i get the No of bits length from NSNumber

Answer 5

I hope it's not too late to answer this thread.

You can try "LibTomMath" which is opensource and free (the author give away this project as public domain). It works out of the box without any configuration, just put all bn_*.c and tommath*.h to your Xcode project and you are ready to go.

#import "tommath.h"

mp_int number1, number2, number3;

mp_init(&number1);
mp_init(&number2);
mp_init(&number3);

mp_read_radix(&number1, "0a120edfff558c98a73015d5d67e8990", 16);
mp_read_radix(&number2, "12e6f45d698c7b7009a841c1348d6ff4", 16);

mp_mul(&number1, &number2, &number3);

char output[1000];
mp_toradix(&number3, output, 16);
NSLog(@"number3:%s", output);

mp_div(&number3, &number1, &number2, NULL);
mp_toradix(&number2, output, 16);
NSLog(@"number2:%s", output);