These old dongles are a joke. The Sentinel Rainbow parallel port dongle for example is merely a "secure" key store that is unlocked using a key with a whooping

These old dongles are a joke. The Sentinel Rainbow parallel port dongle for example is merely a "secure" key store that is unlocked using a key with a whooping length of 16 bits and it uses the "ultra secure" XOR encryption algorithm. The advertised code encryption essentially boils down to having parts of the binary being XOR-ed with some key and to decrypt it, that part of the program would be sent to the dongle and the decrypted text sent back and the program image in memory modified. To make things more difficult the same memory region would be re-used for different texts (who needs re-entrancy anyway). Long story short: This thing does XOR and all caveats of XOR apply. Like XOR-ing the ciphertext with the plaintext will yield the key. So cracking these things boils down to extracting the key and either emulating the dongle or decrypting the "protected" parts of the program and placing them in the binary in the clear. I'd be surprised if your fathers program used something more sophisticated than that.