SigV4 is limited to symmetric HMAC-type signatures which require a shared secret; and many of the specifics are tightly linked to AWS concepts like regions, ser

SigV4 is limited to symmetric HMAC-type signatures which require a shared secret; and many of the specifics are tightly linked to AWS concepts like regions, service names, amz headers and so on. Conceptually, SigV4 is not a whole lot different from a symmetric implementation of this draft; but the draft has support for public key signatures and binds to fewer AWS specificities.