diff --git a/pki.go b/pki.go
new file mode 100644
index 0000000..fdb4e34
--- /dev/null
+++ b/pki.go
@@ -0,0 +1,88 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"strings"
+
+	"golang.org/x/net/trace"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/peer"
+	"google.golang.org/grpc/status"
+)
+
+type clientPKIInfo struct {
+	realm     string
+	principal string
+	job       string
+}
+
+func (c *clientPKIInfo) String() string {
+	return fmt.Sprintf("job=%q, principal=%q, realm=%q", c.job, c.principal, c.realm)
+}
+
+func parseClientName(realm, name string) (*clientPKIInfo, error) {
+	if !strings.HasSuffix(name, "."+realm) {
+		return nil, fmt.Errorf("invalid realm")
+	}
+	service := strings.TrimSuffix(name, "."+realm)
+	parts := strings.Split(service, ".")
+	if len(parts) != 2 {
+		return nil, fmt.Errorf("invalid service")
+	}
+	return &clientPKIInfo{
+		realm:     realm,
+		principal: parts[1],
+		job:       parts[0],
+	}, nil
+}
+
+const (
+	ctxKeyPKIInfo = "hscloud-pki-info"
+)
+
+func withPKIInfo(ctx context.Context, c *clientPKIInfo) context.Context {
+	tr, ok := trace.FromContext(ctx)
+	if ok {
+		tr.LazyPrintf("PKI Peer: %s", c.String())
+	}
+	return context.WithValue(ctx, ctxKeyPKIInfo, c)
+}
+
+func (s *server) unaryInterceptor(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (resp interface{}, err error) {
+	peer, ok := peer.FromContext(ctx)
+	if !ok {
+		s.trace(ctx, "Could not establish identity of peer.")
+		return nil, status.Error(codes.InvalidArgument, "no peer info")
+	}
+
+	authInfo, ok := peer.AuthInfo.(credentials.TLSInfo)
+	if !ok {
+		s.trace(ctx, "Could not establish TLS identity of peer.")
+		return nil, status.Error(codes.InvalidArgument, "no TLS peer info")
+	}
+
+	chains := authInfo.State.VerifiedChains
+	if len(chains) != 1 {
+		s.trace(ctx, "No trusted chain found.")
+		return nil, status.Error(codes.InvalidArgument, "invalid TLS certificate")
+	}
+	chain := chains[0]
+
+	certDNs := make([]string, len(chain))
+	for i, cert := range chain {
+		certDNs[i] = cert.Subject.String()
+	}
+	s.trace(ctx, "TLS chain: %s", strings.Join(certDNs, ", "))
+
+	clientInfo, err := parseClientName(s.opts.pkiRealm, chain[0].Subject.CommonName)
+	if err != nil {
+		s.trace(ctx, "Could not parse certificate DN: %v", err)
+		return nil, status.Error(codes.InvalidArgument, "invalid TLS CommonName")
+	}
+	ctx = withPKIInfo(ctx, clientInfo)
+
+	return handler(ctx, req)
+}