* The Default bound only makes sense for unkeyed hash functions which
can fire up a new engine without a key. Keyed hash functions, like
SipHash24 or Poly1305 require a secret key to be initialized and
should not implement a default engine generator.
* SipHash24 tests updated to the previous default key "0".
Wildcards have been replaced with what is actually used.
In a couple of cases an additional use statement was added to the test
module to import `DisplayHex` which is only used in test, but
previously imported with the wildcard at the top.
BIP324's peer to peer encryption protocol requires an HMAC-based extract
and expand key derivation function (HKDF). HKDFs were not part of many
bitcoin protocols before BIP324, but the hope is that the encrypted
protocol becomes the dominant standard justifying this implementation.
Nick Johnson
Fmt Bot
Jamil Lambert, PhD
Andrew Poelstra