diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 4bb7485..cead98c 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -13,7 +13,7 @@ jobs:
   ci:
     runs-on: ubuntu-latest
     container:
-      image: ghcr.io/tillitis/tkey-builder:4
+      image: ghcr.io/tillitis/tkey-builder:5rc2
     steps:
       - name: checkout
         uses: actions/checkout@v4
diff --git a/RELEASE.md b/RELEASE.md
index 1a3ea35..965ea76 100644
--- a/RELEASE.md
+++ b/RELEASE.md
@@ -1,6 +1,13 @@
 # Release notes
 
+## Upcoming
+
+- Detect new Castor USB VID/PID and older TKey models.
+- Include helpful list of UDI Product ID.
+- Update x/crypto to v0.40.0.
+
 ## v1.1.0
+
 - Change license to BSD-2-Clause
 - Follow REUSE specification, see https://reuse.software/
 - Return payload even if NOK is set in header
diff --git a/go.mod b/go.mod
index e732830..73fcb65 100644
--- a/go.mod
+++ b/go.mod
@@ -1,15 +1,15 @@
 module github.com/tillitis/tkeyclient
 
-go 1.21
+go 1.23.0
 
 require (
 	github.com/ccoveille/go-safecast v1.1.0
 	go.bug.st/serial v1.6.2
-	golang.org/x/crypto v0.22.0
+	golang.org/x/crypto v0.40.0
 )
 
 require (
 	github.com/creack/goselect v0.1.2 // indirect
 	github.com/stretchr/testify v1.8.0 // indirect
-	golang.org/x/sys v0.19.0 // indirect
+	golang.org/x/sys v0.34.0 // indirect
 )
diff --git a/go.sum b/go.sum
index ceceeee..480f084 100644
--- a/go.sum
+++ b/go.sum
@@ -14,10 +14,10 @@ github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PK
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 go.bug.st/serial v1.6.2 h1:kn9LRX3sdm+WxWKufMlIRndwGfPWsH1/9lCWXQCasq8=
 go.bug.st/serial v1.6.2/go.mod h1:UABfsluHAiaNI+La2iESysd9Vetq7VRdpxvjx7CmmOE=
-golang.org/x/crypto v0.22.0 h1:g1v0xeRhjcugydODzvb3mEM9SQ0HGp9s/nh3COQ/C30=
-golang.org/x/crypto v0.22.0/go.mod h1:vr6Su+7cTlO45qkww3VDJlzDn0ctJvRgYbC2NvXHt+M=
-golang.org/x/sys v0.19.0 h1:q5f1RH2jigJ1MoAWp2KTp3gm5zAGFUTarQZ5U386+4o=
-golang.org/x/sys v0.19.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/crypto v0.40.0 h1:r4x+VvoG5Fm+eJcxMaY8CQM7Lb0l1lsmjGBQ6s8BfKM=
+golang.org/x/crypto v0.40.0/go.mod h1:Qr1vMER5WyS2dfPHAlsOj01wgLbsyWtFn/aY+5+ZdxY=
+golang.org/x/sys v0.34.0 h1:H5Y5sJ2L2JRdyv7ROF1he/lPdvFsd0mJHFw2ThKHxLA=
+golang.org/x/sys v0.34.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
diff --git a/ports.go b/ports.go
index c396d29..75d9c4a 100644
--- a/ports.go
+++ b/ports.go
@@ -11,8 +11,10 @@ import (
 )
 
 const (
-	tillitisUSBVID = "1207"
-	tillitisUSBPID = "8887"
+	tillitisMTAUSBV1VID  = "1207"
+	tillitisMTAUSBV1PID  = "8887"
+	tillitisTKEYUSBV2VID = "1209"
+	tillitisTKEYUSBV2PID = "8885"
 	// Custom errors
 	ErrNoDevice    = constError("no TKey connected")
 	ErrManyDevices = constError("more than one TKey connected")
@@ -23,6 +25,11 @@ type SerialPort struct {
 	SerialNumber string
 }
 
+func isTKey(vid string, pid string) bool {
+	return (vid == tillitisMTAUSBV1VID && pid == tillitisMTAUSBV1PID) ||
+		(vid == tillitisTKEYUSBV2VID && pid == tillitisTKEYUSBV2PID)
+}
+
 // DetectSerialPort tries to detect an inserted TKey and returns the
 // device path if successful.
 func DetectSerialPort(verbose bool) (string, error) {
@@ -65,7 +72,7 @@ func GetSerialPorts() ([]SerialPort, error) {
 		return ports, nil
 	}
 	for _, port := range portDetails {
-		if port.IsUSB && port.VID == tillitisUSBVID && port.PID == tillitisUSBPID {
+		if port.IsUSB && isTKey(port.VID, port.PID) {
 			ports = append(ports, SerialPort{port.Name, port.SerialNumber})
 		}
 	}
diff --git a/tkeyclient.go b/tkeyclient.go
index e5a05d3..fefdcc6 100644
--- a/tkeyclient.go
+++ b/tkeyclient.go
@@ -55,6 +55,12 @@ const (
 
 	// Size of RAM in the TKey. See TK1_APP_MAX_SIZE in tk1_mem.h
 	AppMaxSize = 0x20000
+
+	// UDI Product IDs
+	UDIPIDEngSample = 0 // XXX Also used for development purposes
+	UDIPIDAcrab     = 1
+	UDIPIDBellatrix = 2
+	UDIPIDCastor    = 3
 )
 
 // TillitisKey is a serial connection to a TKey and the commands that