HASHING
a hash function takes an input and creates a uniquely mapped gibberish ouptut
sha1 is one of them
Key
a unique object that belongs to someone. used to authorize them.
certificate
contains a key and other meta data. it’s usually itself signed by a trusted certificate issuer.
together, you use this certificate to sign an app.
2 fundamental ways of authenticating someone in a distributed disconnected system like the internet