public abstract class Fnv1aBigBase : HashAlgorithm
{
    /// <summary>
    /// The "wrap-around" modulo value for keeping multiplication within the number of bits.
    /// </summary>
    private readonly BigInteger modValue;

    /// <summary>
    /// The prime.
    /// </summary>
    private readonly BigInteger fnvPrime;

    /// <summary>
    /// The non-zero offset basis.
    /// </summary>
    private readonly BigInteger fnvOffsetBasis;

    /// <summary>
    /// The computed hash value.
    /// </summary>
    private BigInteger hash;

    protected Fnv1aBigBase(BigInteger modValue, BigInteger fnvPrime, BigInteger fnvOffsetBasis)
    {
        this.modValue = modValue;
        this.fnvPrime = fnvPrime;
        this.fnvOffsetBasis = fnvOffsetBasis;
        this.Initialize();
    }

    public override sealed void Initialize()
    {
        this.hash = this.fnvOffsetBasis;
    }

    protected override void HashCore(byte[] array, int ibStart, int cbSize)
    {
        for (var i = ibStart; i < cbSize; i++)
        {
            unchecked
            {
                this.hash ^= array[i];
                this.hash = (this.hash * this.fnvPrime) % this.modValue;
            }
        }
    }

    protected override byte[] HashFinal()
    {
        return this.hash.ToByteArray();
    }
}

public sealed class Fnv1a128 : Fnv1aBigBase
{
    public Fnv1a128() : base(
            BigInteger.Parse("100000000000000000000000000000000", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("0000000001000000000000000000013B", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("6C62272E07BB014262B821756295C58D", NumberStyles.AllowHexSpecifier))
    {
    }
}

public sealed class Fnv1a256 : Fnv1aBigBase
{
    public Fnv1a256() : base(
            BigInteger.Parse("1000000000000000000000000000000000000000000000000000000000000000", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("0000000000000000000001000000000000000000000000000000000000000163", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("0DD268DBCAAC550362D98C384C4E576CCC8B1536847B6BBB31023B4C8CAEE0535", NumberStyles.AllowHexSpecifier))
    {
    }
}

public sealed class Fnv1a512 : Fnv1aBigBase
{
    public Fnv1a512() : base(
            BigInteger.Parse("10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("00000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000000000000000000000000157", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("0B86DB0B1171F4416DCA1E50F309990ACAC87D059C90000000000000000000D21E948F68A34C192F62EA79BC942DBE7CE182036415F56E34BAC982AAC4AFE9FD9", NumberStyles.AllowHexSpecifier))
    {
    }
}

public sealed class Fnv1a1024 : Fnv1aBigBase
{
    public Fnv1a1024() : base(
            BigInteger.Parse("1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("000000000000000000000000000000000000000000000000000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000018D", NumberStyles.AllowHexSpecifier),
            BigInteger.Parse("0000000000000000005F7A76758ECC4D32E56D5A591028B74B29FC4223FDADA16C3BF34EDA3674DA9A21D9000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004C6D7EB6E73802734510A555F256CC005AE556BDE8CC9C6A93B21AFF4B16C71EE90B3", NumberStyles.AllowHexSpecifier))
    {
    }
}