-Message authentication algorithm to use. Default is
-.IB hash -hmac/ halfhashlen \fR,
-where
+Message authentication algorithm to use.
+Default depends on
+.I bulk
+as follows.
+.TS
+center;
+| ci | ci |
+| lb | lb |.
+_
+bulk mac
+_
+v0 \fIhash\fB-hmac/\fIhalfhashlen
+iiv \fIhash\fB-hmac/\fIhalfhashlenrijndael-cbc
+naclbox poly1305/128
+_
+.TE
+.IP
+(In the above,