How can I use bigint with C#?

Question

I work to implement an RSA key algorithm. But I couldn't use a 2048-bit value. How I can use it?

I want to use big integer.

Usually RSA key algorithms work on 8 bits at a time. Your key would be placed in a byte array with 8 indexes. — Trisped, May 16 '12 at 18:54
not duplicate. ı do not want to use long or int64. they do not enough for me — CompEng, May 16 '12 at 18:54

score 31 · Accepted Answer · answered May 16 '12 at 18:56

31

You can use System.Numerics.BigInteger (add a reference to System.Numerics assembly). As mentioned in the comments this might not be the right approach though.

answered May 16 '12 at 18:56

BrokenGlass

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Indeed, BigInteger is the way to go. Minor note: it's only available in .NET 4.0 and higher. – Juliën Nov 05 '13 at 09:06

score 9 · Answer 2 · edited Mar 03 '15 at 17:50

Here's using BigInteger. This method Prints Numbers in the Fibonacci Sequence up to n.

public static void FibonacciSequence(int n)
{
    /** BigInteger easily holds the first 1000 numbers in the Fibonacci Sequence. **/
    List<BigInteger> fibonacci = new List<BigInteger>();
    fibonacci.Add(0);
    fibonacci.Add(1);
    BigInteger i = 2;
    while(i < n)
    {                
        int first = (int)i - 2;
        int second = (int) i - 1;

        BigInteger firstNumber =  fibonacci[first];
        BigInteger secondNumber = fibonacci[second];
        BigInteger sum = firstNumber + secondNumber;
        fibonacci.Add(sum);
        i++;
    }         

    foreach (BigInteger f in fibonacci) { Console.WriteLine(f); }
}

Douglas · Answer 3 · 2012-05-17T05:52:54.493

8

Native support for big integers has been introduced in .NET 4.0. Just add an assembly reference to System.Numerics, add a using System.Numerics; declaration at the top of your code file, and you’re good to go. The type you’re after is BigInteger.

edited May 17 '12 at 05:52

answered May 16 '12 at 18:55

Douglas

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score 3 · Answer 4 · answered May 16 '12 at 18:56

3

BigInteger is available in .NET 4.0 or later. There are some third-party implementations as well (In case you are using an earlier version of the framework).

answered May 16 '12 at 18:56

moribvndvs

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score 1 · Answer 5 · edited Jul 08 '15 at 17:50

1

Better use System.Numerics.BigInteger.

edited Jul 08 '15 at 17:50

Peter Mortensen

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answered May 16 '12 at 19:10

Kishore Kumar

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How can I use bigint with C#?

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