diff --git a/lib/certgen/certgen.go b/lib/certgen/certgen.go
index b18f289..654312a 100644
--- a/lib/certgen/certgen.go
+++ b/lib/certgen/certgen.go
@@ -8,7 +8,6 @@ import (
 	"crypto"
 	"crypto/ecdsa"
 	"crypto/ed25519"
-	"crypto/elliptic"
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha256"
@@ -201,32 +200,6 @@ func GetSignerFromPEMBytes(privateKey []byte) (crypto.Signer, error) {
 	}
 }
 
-func getSignerHashFromPublic(pub interface{}) (crypto.Hash, error) {
-	// crypto.SHA256
-	switch pub := pub.(type) {
-	case *rsa.PublicKey:
-		return crypto.SHA256, nil
-	case *ecdsa.PublicKey:
-		switch pub.Curve {
-		case elliptic.P224(), elliptic.P256():
-			return crypto.SHA256, nil
-		case elliptic.P384():
-			return crypto.SHA384, nil
-		case elliptic.P521():
-			return crypto.SHA512, nil
-		default:
-			return 0, fmt.Errorf("x509: unknown elliptic curve")
-		}
-	//Ed25519 signatures (by default) dont have a prefered signer
-	case *ed25519.PublicKey, ed25519.PublicKey:
-		return 0, nil
-
-	default:
-		return 0, fmt.Errorf("unknown key type")
-	}
-
-}
-
 // ValidatePublicKeyStrenght checks if the "strength" of the key is good enough to be considered secure
 // At this moment it checks for sizes of parameters only. For RSA it means bits>=2041 && exponent>=65537,
 // For EC curves it means bitsize>=256. ec25519 is considered secure. All other public keys are not
@@ -266,6 +239,31 @@ func derBytesCertToCertAndPem(derBytes []byte) (*x509.Certificate, string, error
 }
 */
 
+// On the initial version of keymaster we used the base64 encoding
+// of the sha256sum of the rsa signature of the sha256 of the
+// common name. This to have a stable, key dependent
+// serial number.
+// However this was a bad idea as:
+// 1. Not all signers can use sha256
+// 2. Not all signatures are stable.
+//
+// Thus we will keep the rsa behaviour for compatiblity reasons
+// But for all other keys we will just return the pkix asn1 encoding
+// of the public key
+func getKMCompatbileKeyStableBytesForSerial(priv interface{}, commonName []byte) ([]byte, error) {
+	switch v := priv.(type) {
+	case *rsa.PrivateKey:
+		sum := sha256.Sum256(commonName)
+		return v.Sign(rand.Reader, sum[:], crypto.SHA256)
+	case *ecdsa.PrivateKey:
+		return x509.MarshalPKIXPublicKey(v.Public())
+	case ed25519.PrivateKey:
+		return x509.MarshalPKIXPublicKey(v.Public())
+	default:
+		return nil, fmt.Errorf("Type not recognized  %T!\n", v)
+	}
+}
+
 // return both an internal representation an the pem representation of the string
 // As long as the issuer value matches THEN the serial number can be different every time
 func GenSelfSignedCACert(commonName string, organization string, caPriv crypto.Signer) ([]byte, error) {
@@ -278,16 +276,11 @@ func GenSelfSignedCACert(commonName string, organization string, caPriv crypto.S
 	if err != nil {
 		return nil, err
 	}
-	sum := sha256.Sum256([]byte(commonName))
-	hashfunc, err := getSignerHashFromPublic(caPriv.Public())
-	if err != nil {
-		return nil, err
-	}
-	signedCN, err := caPriv.Sign(rand.Reader, sum[:], hashfunc)
+	keyStableBytes, err := getKMCompatbileKeyStableBytesForSerial(caPriv, []byte(commonName))
 	if err != nil {
 		return nil, err
 	}
-	sigSum := sha256.Sum256(signedCN)
+	sigSum := sha256.Sum256(keyStableBytes)
 	sig := base64.StdEncoding.EncodeToString(sigSum[:])
 	template := x509.Certificate{
 		SerialNumber: serialNumber,
diff --git a/lib/certgen/certgen_test.go b/lib/certgen/certgen_test.go
index 84d9ad0..326f5dc 100644
--- a/lib/certgen/certgen_test.go
+++ b/lib/certgen/certgen_test.go
@@ -1,6 +1,7 @@
 package certgen
 
 import (
+	"bytes"
 	"crypto"
 	"crypto/sha256"
 	"crypto/x509"
@@ -215,6 +216,22 @@ AAAECdSciYZnODYp2QC0s838bYh8d2XEOuvBOqcOEA6MUjL8gKfkOxEiNHgbIpVQ+5xYns
 Df7tMqg18r8iaCVRzqyFAAAAHWN2aWVjY29AY3ZpZWNjby0tTWFjQm9va1BybzE1
 -----END OPENSSH PRIVATE KEY-----`
 
+// We should not be using p224 keys except for testing
+// openssl ecparam -name secp224r1 -genkey
+const testP224Privatekey = `-----BEGIN EC PRIVATE KEY-----
+MGgCAQEEHNBN+rQ+YDZ27lRc6tHu5myU+kq8Tetzodw4bfOgBwYFK4EEACGhPAM6
+AARWr9bjMJaYzHyQjD2za224ohGmBg6/6H5pomxWY8fkAfZy/DmjRRCD72pX86xp
+PSDtPZDi9/ao4g==
+-----END EC PRIVATE KEY-----`
+
+// The tranformation requires the full information of the private key
+//
+//	openssl ec -in private.ec.key -pubout
+const testP224PublicKey = `-----BEGIN PUBLIC KEY-----
+ME4wEAYHKoZIzj0CAQYFK4EEACEDOgAEVq/W4zCWmMx8kIw9s2ttuKIRpgYOv+h+
+aaJsVmPH5AH2cvw5o0UQg+9qV/OsaT0g7T2Q4vf2qOI=
+-----END PUBLIC KEY-----`
+
 const testDuration = time.Duration(120 * time.Second)
 
 // SSSD tests do require some setup... in this case we do some checks to ensure
@@ -541,6 +558,8 @@ func TestGenx509CertGoodWithRealm(t *testing.T) {
 // GenSelfSignedCACert
 func TestGenSelfSignedCACertGood(t *testing.T) {
 	validPemKeys := []string{testSignerPrivateKey, pkcs8ecPrivateKey, pkcs8Ed25519PrivateKey}
+	publcKeyPems := []string{testUserPEMPublicKey, testP224PublicKey}
+
 	for _, signerPem := range validPemKeys {
 		caPriv, err := GetSignerFromPEMBytes([]byte(signerPem))
 		if err != nil {
@@ -557,16 +576,30 @@ func TestGenSelfSignedCACertGood(t *testing.T) {
 		}
 		t.Logf("got '%s'", pemCert)
 
-		// Now we use it to generate a user Cert
-		userPub, err := getPubKeyFromPem(testUserPEMPublicKey)
+		derCaCert2, err := GenSelfSignedCACert("some hostname", "some organization", caPriv)
 		if err != nil {
 			t.Fatal(err)
 		}
-		_, err = GenUserX509Cert("username", userPub, cert, caPriv, nil,
-			testDuration, nil, nil, nil, testlogger.New(t))
+		cacert2, _, err := derBytesCertToCertAndPem(derCaCert2)
 		if err != nil {
 			t.Fatal(err)
 		}
+		if !bytes.Equal(cert.RawSubject, cacert2.RawSubject) {
+			t.Fatalf("subjects across generations should match")
+		}
+
+		// Now we use it to generate a user Cert
+		for _, publicPem := range publcKeyPems {
+			userPub, err := getPubKeyFromPem(publicPem)
+			if err != nil {
+				t.Fatal(err)
+			}
+			_, err = GenUserX509Cert("username", userPub, cert, caPriv, nil,
+				testDuration, nil, nil, nil, testlogger.New(t))
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
 		//t.Logf("got '%s'", certString)
 	}