currently, I'm working Shamir Secret Sharing algorithm and for not so big numbers (long passwords more than 7 chars) my calculations are broken because of overflows.
The case is this: I have a big number: suppose 49584309583 and if I use it in calculations eventually be lost of precision so I've heard that calculations can be done in Galois Field (GF) for example in $\operatorname{GF}(251)$
So the question is: can I get my number to be converted back from $\operatorname{GF}$ to outside $\operatorname{GF}$?