A software dongle is hardware that looks like a USB flash drive and needs to be purchased from a dongle manufacturer.
If you are your own encryption software, you can buy a dongle after the development kit they provide to develop, generally have the corresponding example reference, C# is generally supported. It is best to compare a number of companies before buying, some dongle manufacturers development kits are also charged separately, you can try the ROCKEY series, only the cost of hardware dogs.
If you want to copy the dongle according to the existing software then it is more trouble, now the dongle more try smart card chip, hardware can not be copied, want to guess what is written in the dongle is not easy to get, unless the software encryption strength is very low.