This now uses one hkdf on the X25519 shared secret to create
a key for the sender and receiver.
The hkdf call is now just called upon the computed shared
secret, since the shared secret is a function of the pubkeys.
The nonces now start at 0, as we are using chacha as a stream
cipher, and the sender and receiver now have different keys.
Generate keys with HKDF instead of hash functions, which provides better security properties.
Add xchacha20poly1305 to secret connection. (Due to rebasing, this code has been removed)
* use increment and decrement operators.
* remove unnecessary else branches.
* fix package comment with leading space.
* fix receiver names.
* fix error strings.
* remove omittable code.
* remove redundant return statement.
* Revert changes (code is generated.)
* use cfg as receiver name for all config-related types.
* use lsi as the receiver name for the LastSignedInfo type.
Updates https://github.com/tendermint/tendermint/issues/850
My security alarms falsely blarred when I skimmed and noticed
keys being compared with `==`, without the proper context
so I mistakenly filed an issue, yet the purpose of that
comparison was to check if the local ephemeral public key
was just the least, sorted lexicographically.
Anyways, let's use the proper bytes.Equal check, to save future labor.