diff --git a/goblins/ocapn/captp.rkt b/goblins/ocapn/captp.rkt
index 64bd8b1..e1d946e 100644
--- a/goblins/ocapn/captp.rkt
+++ b/goblins/ocapn/captp.rkt
@@ -38,6 +38,7 @@
          "structs-urls.rkt"
          (submod "structs-urls.rkt" marshall)
          "define-recordable-struct.rkt"
+         "crypto-converters.rkt"
 
          syrup
 
@@ -1394,12 +1395,12 @@
           ;; TODO: Shouldn't the netlayer actually interpret this message
           ;;   before it gets here?  Ie, at this stage, we're already
           ;;   "confident" this is from the right location
-          [(mtp:op:start-session (and remote-encoded-pubkey
-                                      (list 'eddsa 'public 'ed25519 _))
+          [(mtp:op:start-session remote-encoded-pubkey
                                  (? ocapn-machine? claimed-remote-location)
                                  remote-location-sig)
+           (pk 'got-to-start-session)
            (define remote-handoff-pubkey
-             (datum->pk-key remote-encoded-pubkey 'rkt-public))
+             (datum->pk-key (gcrypt->racket/public-key remote-encoded-pubkey) 'rkt-public))
            ;; TODO: I guess we didn't know by the time this was opened
            ;;   what the remote location was going to be... that's part of the reason
            ;;   for the start-session message...
@@ -1411,7 +1412,7 @@
            (unless (pk-verify remote-handoff-pubkey
                               (syrup-encode (record* 'my-location claimed-remote-location)
                                             #:marshallers marshallers)
-                              remote-location-sig)
+                              (gcrypt->racket/signature remote-location-sig))
              (error "Location not signed by handoff key"))
 
            ;; TODO: Now we need to do the dial back and verify that
@@ -1484,9 +1485,9 @@
 
       ;; Now we'll need to send our side of the start-session and get the
       ;; other side... which will be handled by the ^setup-completer above
-      (send-to-remote (mtp:op:start-session handoff-pubkey
+      (send-to-remote (mtp:op:start-session (racket->gcrypt/public-key handoff-pubkey)
                                             our-location
-                                            our-location-sig))
+                                            (racket->gcrypt/signature our-location-sig)))
       
       ;; Return the meta-bootstrap-vow, which will be completed as above
       meta-bootstrap-vow]
diff --git a/goblins/ocapn/crypto-converters.rkt b/goblins/ocapn/crypto-converters.rkt
new file mode 100644
index 0000000..1557d0b
--- /dev/null
+++ b/goblins/ocapn/crypto-converters.rkt
@@ -0,0 +1,48 @@
+#lang racket
+
+;;; Copyright 2022 Jessica Tallon
+;;;
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
+;;;
+;;;    http://www.apache.org/licenses/LICENSE-2.0
+;;;
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
+
+(provide racket->gcrypt/public-key
+         gcrypt->racket/public-key
+
+         racket->gcrypt/signature
+         gcrypt->racket/signature)
+
+(require racket/match)
+
+(define (racket->gcrypt/public-key public-key)
+  (match public-key
+    [(list 'eddsa 'public 'ed25519 data)
+     `(public-key (ecc (curve Ed25519) (flags eddsa) (q ,data)))]
+    [_ (error "Don't know how to encode key: ~a" public-key)]))
+
+(define (gcrypt->racket/public-key public-key)
+  (match public-key
+    [`(public-key (ecc (curve Ed25519) (flags eddsa) (q ,data)))
+     `(eddsa public ed25519 ,data)]))
+
+(define (racket->gcrypt/signature signature)
+  (let ((r (subbytes signature 0 32))
+        (s (subbytes signature 32)))
+    `(sig-val (eddsa (r ,r) (s ,s)))))
+
+(define (gcrypt->racket/signature signature)
+  (match signature
+    [`(sig-val (eddsa (r ,r) (s ,s)))
+     (bytes-append r
+                   (make-bytes (- 32 (bytes-length r)) 0)
+                   s
+                   (make-bytes (- 32 (bytes-length s)) 0))]
+    [_ (error "No matching signature: ~a" signature)]))