* the key material; between @k + x@ and @k + y@ is `your'
* contribution; and between @k + y@ and @k + z@ is a shared
* value we made together. These are used to construct two
- * pairs of symmetric keys. Each pair consists of an encryption
- * key and a message authentication key. One pair is used for
- * outgoing messages, the other for incoming messages.
+ * collections of symmetric keys: one for outgoing messages, the
+ * other for incoming messages.
*
* The new key is marked so that it won't be selected for output
* by @ksl_encrypt@. You can still encrypt data with it by