diff --git a/BTP.markdown b/BTP.markdown
index 9bd550b..10af7ff 100644
--- a/BTP.markdown
+++ b/BTP.markdown
@@ -55,7 +55,7 @@ If a sender starts sending a stream at time *t* according to the sender's clock,
 
 The four initial keys derived from *S* are the keys for period *P - 1*. The keys for each subsequent period *i* are derived from the previous period's keys as follows:
 
-* *next_ock = KDF(ock, "ROTATE", int(64, i))*
-* *next_ick = KDF(ick, "ROTATE", int(64, i))*
-* *next_otk = KDF(otk, "ROTATE", int(64, i))*
-* *next_itk = KDF(itk, "ROTATE", int(64, i))*
+* *next_ock = KDF(ock, "ROTATE_OUTGOING_CIPHER_KEY", int(64, i))*
+* *next_ick = KDF(ick, "ROTATE_INCOMING_CIPHER_KEY", int(64, i))*
+* *next_otk = KDF(otk, "ROTATE_OUTGOING_TAG_KEY", int(64, i))*
+* *next_itk = KDF(itk, "ROTATE_INCOMING_TAG_KEY", int(64, i))*