diff --git a/src/authentic2/saml/saml2utils.py b/src/authentic2/saml/saml2utils.py
index 42d93306a..f3a8d645c 100644
--- a/src/authentic2/saml/saml2utils.py
+++ b/src/authentic2/saml/saml2utils.py
@@ -57,13 +57,6 @@ def bool2xs(boolean):
     raise TypeError()
 
 
-def int_to_b64(i):
-    h = hex(i)[2:].strip('L')
-    if len(h) % 2 == 1:
-        h = '0' + h
-    return base64.b64encode(binascii.unhexlify(h))
-
-
 def keyinfo(tb, key):
     tb.pushNamespace(lasso.DS_HREF)
     tb.start('KeyInfo', {})
@@ -78,10 +71,14 @@ def keyinfo(tb, key):
         tb.start('KeyValue', {})
         tb.start('RSAKeyValue', {})
         tb.start('Modulus', {})
-        tb.data(int_to_b64(x509utils.get_rsa_public_key_modulus(key)))
+        tb.data(
+            x509utils.int_to_cryptobinary(
+                x509utils.get_rsa_public_key_modulus(key)))
         tb.end('Modulus')
         tb.start('Exponent', {})
-        tb.data(int_to_b64(x509utils.get_rsa_public_key_exponent(key)))
+        tb.data(
+            x509utils.int_to_cryptobinary(
+                x509utils.get_rsa_public_key_exponent(key)))
         tb.end('Exponent')
         tb.end('RSAKeyValue')
         tb.end('KeyValue')
diff --git a/src/authentic2/saml/x509utils.py b/src/authentic2/saml/x509utils.py
index 1f6e843bf..3c14fe839 100644
--- a/src/authentic2/saml/x509utils.py
+++ b/src/authentic2/saml/x509utils.py
@@ -162,25 +162,20 @@ def can_generate_rsa_key_pair():
         return False
 
 
-def get_xmldsig_rsa_key_value(publickey):
-    def int_to_bin(i):
-        h = hex(i)[2:].strip('L')
-        if len(h) % 2 == 1:
-            h = '0' + h
-        return binascii.unhexlify(h)
+def int_to_cryptobinary(integer):
+    # ref: https://www.w3.org/TR/xmldsig-core1/#sec-CryptoBinary
+    byte_length = (integer.bit_length() + 7) // 8
+    integer_bytes = integer.to_bytes(byte_length, byteorder='big')
+    return base64.b64encode(integer_bytes).decode('ascii')
 
+
+def get_xmldsig_rsa_key_value(publickey):
     mod = get_rsa_public_key_modulus(publickey)
     exp = get_rsa_public_key_exponent(publickey)
-    mod_byte_length = (mod.bit_length() + 7) // 8
-    exp_byte_length = (exp.bit_length() + 7) // 8
-    mod_bytes = mod.to_bytes(mod_byte_length, byteorder='big')
-    exp_bytes = exp.to_bytes(exp_byte_length, byteorder='big')
-    mod_cryptobinary = base64.b64encode(mod_bytes).decode('ascii')
-    exp_cryptobinary = base64.b64encode(exp_bytes).decode('ascii')
     return (
         '<RSAKeyValue xmlns="http://www.w3.org/2000/09/xmldsig#">\n\t'
         '<Modulus>%s</Modulus>\n\t'
         '<Exponent>%s</Exponent>\n</RSAKeyValue>' % (
-            mod_cryptobinary,
-            exp_cryptobinary)
-    )
+            int_to_cryptobinary(mod),
+            int_to_cryptobinary(exp),
+    ))
diff --git a/tests/test_idp_saml2.py b/tests/test_idp_saml2.py
index 572e31de0..182bc38dc 100644
--- a/tests/test_idp_saml2.py
+++ b/tests/test_idp_saml2.py
@@ -955,3 +955,16 @@ def test_add_attributes_user_ou1_role_ou2(add_attributes_all, user_ou1, role_ou2
         'django_user_uuid': set([user_ou1.uuid]),
         'is_admin': set(['true']),
     }
+
+
+def test_metadata_with_openssl_public_key(app, idp, settings):
+    settings.A2_IDP_SAML2_SIGNATURE_PUBLIC_KEY = '''-----BEGIN PUBLIC KEY-----
+MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvxFkfPdndlGgQPDZgFGX
+brNAc/79PULZBuNdWFHDD9P5hNhZn9Kqm4Cp06Pe/A6u+g5wLnYvbZQcFCgfQAEz
+ziJtb3J55OOlB7iMEI/T2AX2WzrUH8QT8NGhABONKU2Gg4XiyeXNhH5R7zdHlUwc
+Wq3ZwNbtbY0TVc+n665EbrfV/59xihSqsoFrkmBLH0CoepUXtAzA7WDYn8AzusIu
+Mx3n8844pJwgxhTB7Gjuboptlz9Hri8JRdXiVT9OS9Wt69ubcNoM6zuKASmtm48U
+uGnhj8v6XwvbjKZrL9kA+xf8ziazZfvvw/VGTm+IVFYB7d1x457jY5zjjXJvNyso
+owIDAQAB
+-----END PUBLIC KEY-----'''
+    response = app.get('/idp/saml2/metadata')