When you sign up with snort.social they show you the mnemonic seed, and the corresponding public keys as well as one private key that starts with nsec. But what about the hexadecimal private key? Why are they hiding it from their user? How might I generate it given my mnemonic phrase? Where is the software that snort.social uses to generate a private key? I mean where is it published, I don't mean the location of their servers. I would like to generate the keys myself with such software just to make sure that the keys are correct.