bitcoin-wallet salvage

const Int32 n = 120;  // Output number of the puzzle tx

Byte[] rnd256 = new Byte[32];
var random = new Random();
random.NextBytes(rnd256); // Get 256-bit random sequence  

Int32 nBytes = (n - 1) / 8;
Int32 nBits = (n - 1) % 8;
Byte mask = (Byte)(0xFF >> (8 - nBits));

for (UInt32 i = 0; i < 32 - nBytes - 1; i++) rnd256[i] = 0; // Zeroing unused bytes
rnd256[32 - nBytes - 1] &= mask;                            // Zeroing unused bits                     
rnd256[32 - nBytes - 1] |= (Byte)(mask + 1);                // Most significant bit is always 1.

String rndHex = BitConverter.ToString(rnd256).Replace("-", String.Empty);

Console.WriteLine(rndHex);

UInt64 Base = 0x7FFFFFFFFFFFFFFF;
            
var random = new Random();

UInt64 high32Rnd = (UInt64)random.Next();
UInt64 low32Rnd = (UInt64)random.Next();

UInt64 rnd64 = (high32Rnd << 32) | low32Rnd;
rnd64 >>= 1;
rnd64 += Base;

Console.WriteLine(rnd64);