At 45:43 in this video (from the Princeton Coursera Bitcoin and CryptoCurrency Course), they talk about GoofyCoin and show the image below.
My question is, why does it say "signed by pk"... isn't the actual signing done using the "sk", and the verification done using the "pk"?
Update: I think I figured out what's going on here, and am leaving this here for future reference.
signed by pk(goofy) means "signed by the identity of goofy" because as mentioned in an earlier video,
pk = identity