Use the Windows Crypto API for Pseudo-Random Data Generation

function GenerateRandom(Len:Cardinal): String;
// uses the MS CSPRNG to produce Len bytes into a string.  Returns the data in
// a string of len bytes.

var
  hProv: TCryptProv;
begin
  if not CryptAcquireContext(hProv, nil, MS_ENHANCED_PROV, PROV_RSA_FULL,
         CRYPT_VERIFYCONTEXT) then
    CryptAcquireContext(hProv, nil, MS_ENHANCED_PROV, PROV_RSA_FULL,
         CRYPT_NEWKEYSET + CRYPT_VERIFYCONTEXT);
  if hProv > 0 then
    try
      SetLength(Result, Len);
      CryptGenRandom(hProv, Len, @Result[1]);
    finally
      CryptReleaseContext(hProv, 0);
    end;
end;