anchor.diff:           dist_handle,
            hmac_algorithm = sha256,
            aead_cipher = aes_gcm,
  +         shared_secret,
            iv = 12,
            key = 16,
            tag_len = 16,
  
positive.code:                     {Key2B, IV2B} =
                          hmac_key_iv(
                            HmacAlgo, SharedSecret, [R2B, R3A], KeyLen, IVLen),
                      RecvParams = Params#params{key = Key2B, iv = IV2B},
                      %%
                      {SendParams, RecvParams, StartMsg}
              end
  
negative.code:                     {Key2A, IV2A} =
                          hmac_key_iv(
                            HmacAlgo, SharedSecret, [R2A, R3B], KeyLen, IVLen),
                      SendParams =
                          Params#params{
                            shared_secret = SharedSecret,
                            key = Key2A, iv = IV2A},
                      %%
                      StartCleartext = [R2B, R3B, <<RekeyInterval:32>>],
                      StartMsgLen = TagLen + iolist_size(StartCleartext),
  