4 files changed, 32 insertions, 7 deletions

diff --git a/ecdsa.go b/ecdsa.go
index 8bf432d..4202bd6 100644
--- a/ecdsa.go
+++ b/ecdsa.go
@@ -108,15 +108,23 @@ func LoadPublicKeyEcdsa(raw []byte) (*EcdsaPublicKey, error) {
 	return &EcdsaPublicKey{pub}, nil
 }
 
+// ToPem returns the pem block of the public key.
+func (pu *EcdsaPublicKey) ToPem() (pem.Block, error) {
+	asn1, err := x509.MarshalPKIXPublicKey(pu.public_key)
+	if err != nil {
+		return pem.Block{}, err
+	}
+	return pem.Block{Type: PemLabelPublic, Bytes: asn1}, nil
+}
+
 // This function implements the Pemmer interface to marshal the public key into
 // a pem block.
 func (pu *EcdsaPublicKey) MarshalPem() (io.WriterTo, error) {
-	asn1, err := x509.MarshalPKIXPublicKey(pu.public_key)
-	if err != nil {
+	if block, err := pu.ToPem(); err != nil {
 		return nil, err
+	} else {
+		return marshalledPemBlock(pem.EncodeToMemory(&block)), nil
 	}
-	pem_block := pem.Block{Type: PemLabelPublic, Bytes: asn1}
-	return marshalledPemBlock(pem.EncodeToMemory(&pem_block)), nil
 }
 
 // This function verifies a message using the public key, signature and hash
diff --git a/ed25519.go b/ed25519.go
index f7a0e12..cb56a70 100644
--- a/ed25519.go
+++ b/ed25519.go
@@ -92,9 +92,17 @@ func LoadPublicKeyEd25519(raw []byte) (*Ed25519PublicKey, error) {
 	return &Ed25519PublicKey{pu_loaded}, nil
 }
 
+// ToPem returns the pem encoded public key.
+func (pu Ed25519PublicKey) ToPem() (pem.Block, error) {
+	return pem.Block{Type: PemLabelPublic, Bytes: pu.public_key[:]}, nil
+}
+
 // Export the public key into the pem format.
 func (pu Ed25519PublicKey) MarshalPem() (io.WriterTo, error) {
-	pem_block := pem.Block{Type: PemLabelPublic, Bytes: pu.public_key[:]}
+	pem_block, err := pu.ToPem()
+	if err != nil {
+		return nil, err
+	}
 	return marshalledPemBlock(pem.EncodeToMemory(&pem_block)), nil
 }
 
diff --git a/rsa.go b/rsa.go
index 7d575cb..b4024ac 100644
--- a/rsa.go
+++ b/rsa.go
@@ -86,13 +86,21 @@ func LoadPublicKeyRsa(raw []byte) (*RsaPublicKey, error) {
 	return pub, nil
 }
 
+// ToPem returns the pem encoded public key.
+func (pu *RsaPublicKey) ToPem() (pem.Block, error) {
+	asn1, err := x509.MarshalPKIXPublicKey(pu.public_key)
+	if err != nil {
+		return pem.Block{}, err
+	}
+	return pem.Block{Type: PemLabelPublic, Bytes: asn1}, nil
+}
+
 // marshal a rsa public key into pem format
 func (pu *RsaPublicKey) MarshalPem() (io.WriterTo, error) {
-	asn1, err := x509.MarshalPKIXPublicKey(pu.public_key)
+	pem_block, err := pu.ToPem()
 	if err != nil {
 		return nil, err
 	}
-	pem_block := pem.Block{Type: PemLabelPublic, Bytes: asn1}
 	return marshalledPemBlock(pem.EncodeToMemory(&pem_block)), nil
 }
 
diff --git a/types.go b/types.go
index 53db1a9..f2c6902 100644
--- a/types.go
+++ b/types.go
@@ -45,6 +45,7 @@ type (
 	// same functionality like verifying a message against a signature.
 	PublicKey interface {
 		Pemmer
+		PemOutput
 		// This function can be used to verify a message against a provided signature
 		// using the given hash function.
 		Verify(message []byte, signature []byte, hash crypto.Hash) (bool, error)