Can you comment on the technical specifics of what is inside the activation code SimplEOS generates during account creation? is it some sort of hashed version of your public key?


This is only a base64 payload for your account name and public keys. You can just use any base64 to string decoder to verify the code. Its only on that form to prevent you to mistype any info. The code doesn’t contain your private keys, just your public keys and your desired account name.