diff --git a/BTP.markdown b/BTP.markdown
index c3c2abb..433aebd 100644
--- a/BTP.markdown
+++ b/BTP.markdown
@@ -47,7 +47,7 @@ Each device derives four initial keys from S:
 * btk = KDF(S, "BOB_TAG_KEY")
 * bck = KDF(S, "BOB_CIPHER_KEY")
 
-Alice initialises her outgoing tag and cipher keys to otk = atk and ock = ack, and her incoming tag and cipher keys to itk = btk and ick = bck. Bob initialises his outgoing tag and cipher keys to otk = btk and ock = bck, and his incoming tag and cipher keys to itk = atk and ick = ack. Thus Alice's outgoing keys are Bob's incoming keys and vice versa. Both devices then erase S.
+Alice initialises her outgoing tag and cipher keys otk = atk and ock = ack, and her incoming tag and cipher keys itk = btk and ick = bck. Bob initialises his outgoing tag and cipher keys otk = btk and ock = bck, and his incoming tag and cipher keys itk = atk and ick = ack. Thus Alice's outgoing keys are Bob's incoming keys and vice versa. Both devices then erase S.
 
 ### Key rotation