diff --git a/crates/arti-rpcserver/Cargo.toml b/crates/arti-rpcserver/Cargo.toml
index c21b7d76a..38725d78f 100644
--- a/crates/arti-rpcserver/Cargo.toml
+++ b/crates/arti-rpcserver/Cargo.toml
@@ -36,7 +36,7 @@ rand = "0.8"
 serde = { version = "1.0.103", features = ["derive"] }
 serde_json = "1.0.50"
 thiserror = "1"
-tiny-keccak = { version = "2", features = ["k12"] }
+tiny-keccak = { version = "2", features = ["kmac"] }
 tor-async-utils = { path = "../tor-async-utils", version = "0.1.1" }
 tor-bytes = { path = "../tor-bytes", version = "0.7.1" }
 tor-error = { path = "../tor-error", version = "0.5.1" }
diff --git a/crates/arti-rpcserver/src/globalid.rs b/crates/arti-rpcserver/src/globalid.rs
index 696e1a465..fd4402eee 100644
--- a/crates/arti-rpcserver/src/globalid.rs
+++ b/crates/arti-rpcserver/src/globalid.rs
@@ -64,20 +64,10 @@ impl MacKey {
     ///
     /// The current construction allows `out` to be any length.
     fn mac(&self, inp: &[u8], out: &mut [u8]) {
-        use tiny_keccak::{Hasher as _, KangarooTwelve as K12};
-        // This is the HopMAC construction from draft-irtf-cfrg-kangarootwelve-10:
-        //
-        //     HopMAC(Key, M, C, L) = K12(Key, K12(M, C, 32), L)
-        //
-        // TODO RPC: Just use KMAC or something.
-        let mut inner = K12::new(b"artirpc globalid");
-        let mut hash = [0_u8; 32];
-        inner.update(inp);
-        inner.finalize(&mut hash);
-
-        let mut outer = K12::new(hash);
-        outer.update(&self.key[..]);
-        outer.finalize(out);
+        use tiny_keccak::{Hasher as _, Kmac};
+        let mut mac = Kmac::v128(&self.key[..], b"artirpc globalid");
+        mac.update(inp);
+        mac.finalize(out);
     }
 }