Fix typo

whitepaper/zssp.tex

@@ -198,7 +198,7 @@ If we disable all security features, we get \emph{Opportunistic Mode} ZSSP. This
 	\item Double Key-Compromise MitM -- The attacker has the static private keys of two peers, and attempts to become a Man-in-the-Middle between them.
 \end{itemize}
 
-Opportunistic mode ZSSP is vulnerable to Compromise-and-Impersonate and Double Key-Compromise MitM because an attacker can perform a downgrade attack to reset one or both peer's ratchet keys to zero. Howeve because such a downgrade should not normally happen between honest peers, if one does occur we can warn the user it has occurred, allowing them to investigate out-of-band whether them or their peer has corrupted or lost their persistent storage. If both peers have not corrupted their persistent storage a downgrade attack has almost certainly occurred, and one or more static keys are compromised.
+Opportunistic mode ZSSP is vulnerable to Compromise-and-Impersonate and Double Key-Compromise MitM because an attacker can perform a downgrade attack to reset one or both peer's ratchet keys to zero. However because such a downgrade should not normally happen between honest peers, if one does occur we can warn the user it has occurred, allowing them to investigate out-of-band whether them or their peer has corrupted or lost their persistent storage. If both peers have not corrupted their persistent storage a downgrade attack has almost certainly occurred, and one or more static keys are compromised.
 
 Compromise-and-Impersonate and Double Key-Compromise MitM attacks are possible against persistent mode ZSSP for a brief window of time. When an attacker compromises a peer, and steals their ratchet keys along with their static private keys, they have a limited time during with they can perform an impersonation attack. Otherwise the peer will engage in new key exchanges and rotate out the compromised ratchet keys. Furthermore, if the attacker commits to an impersonation attack, this will permanently desynchronize the compromised peer's ratchet keys from the peer being impersonated to. If the attacker does not commit to becoming a permanent MitM from that point onwards, their impersonation attack will be detected.