diff --git a/library/ssl_misc.h b/library/ssl_misc.h
index 119826f..783b823 100644
--- a/library/ssl_misc.h
+++ b/library/ssl_misc.h
@@ -2058,6 +2058,8 @@
         }
         return( 0 );
 }
+
+
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
 
 static inline int mbedtls_ssl_sig_alg_is_supported(
@@ -2141,6 +2143,102 @@
     ((void) sig_alg);
     return( 0 );
 }
+
+#if defined(MBEDTLS_SSL_PROTO_TLS1_3)
+
+static inline int mbedtls_ssl_tls13_sig_alg_is_available_for_pk(
+                mbedtls_ssl_context *ssl,
+                uint16_t sig_alg,
+                mbedtls_pk_context *key)
+{
+    mbedtls_pk_type_t pk_type = mbedtls_ssl_sig_from_pk( key );
+    size_t key_size = mbedtls_pk_get_bitlen( key );
+
+    if( !mbedtls_ssl_sig_alg_is_supported( ssl, sig_alg ) )
+        return( 0 );
+
+    switch( pk_type )
+    {
+#if defined(MBEDTLS_ECDSA_C)
+        case MBEDTLS_SSL_SIG_ECDSA:
+            switch( key_size )
+            {
+#if defined(MBEDTLS_SHA256_C) && defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED)
+                case 256:
+                    return(
+                        sig_alg == MBEDTLS_TLS1_3_SIG_ECDSA_SECP256R1_SHA256 );
+#endif /* MBEDTLS_SHA256_C && MBEDTLS_ECP_DP_SECP256R1_ENABLED */
+
+#if defined(MBEDTLS_SHA384_C) && defined(MBEDTLS_ECP_DP_SECP384R1_ENABLED)
+                case 384:
+                    return(
+                        sig_alg == MBEDTLS_TLS1_3_SIG_ECDSA_SECP384R1_SHA384 );
+#endif /* MBEDTLS_SHA384_C && MBEDTLS_ECP_DP_SECP384R1_ENABLED */
+
+#if defined(MBEDTLS_SHA512_C) && defined(MBEDTLS_ECP_DP_SECP521R1_ENABLED)
+                case 521:
+                    return(
+                        sig_alg == MBEDTLS_TLS1_3_SIG_ECDSA_SECP521R1_SHA512 );
+#endif /* MBEDTLS_SHA512_C && MBEDTLS_ECP_DP_SECP521R1_ENABLED */
+                default:
+                    break;
+            }
+            break;
+#endif /* MBEDTLS_ECDSA_C */
+
+#if defined(MBEDTLS_RSA_C)
+        case MBEDTLS_SSL_SIG_RSA:
+            switch( sig_alg )
+            {
+#if defined(MBEDTLS_PKCS1_V21)
+#if defined(MBEDTLS_SHA256_C)
+                case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA256:
+                    return( key_size <= 2048 );
+#endif /* MBEDTLS_SHA256_C */
+
+#if defined(MBEDTLS_SHA384_C)
+                case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA384:
+                    return( key_size <= 3072 );
+#endif /* MBEDTLS_SHA384_C */
+
+#if defined(MBEDTLS_SHA512_C)
+                case MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA512:
+                    return( key_size <= 4096 );
+#endif /* MBEDTLS_SHA512_C */
+#endif /* MBEDTLS_PKCS1_V21 */
+
+#if defined(MBEDTLS_PKCS1_V15)
+#if defined(MBEDTLS_SHA256_C)
+                case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA256:
+                    return( key_size <= 2048 );
+#endif /* MBEDTLS_SHA256_C */
+
+#if defined(MBEDTLS_SHA384_C)
+                case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA384:
+                    return( key_size <= 3072 );
+#endif /* MBEDTLS_SHA384_C */
+
+#if defined(MBEDTLS_SHA512_C)
+                case MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA512:
+                    return( key_size <= 4096 );
+#endif /* MBEDTLS_SHA512_C */
+#endif /* MBEDTLS_PKCS1_V15 */
+
+                default:
+                    break;
+            }
+            break;
+#endif /* MBEDTLS_RSA_C */
+
+        default:
+            break;
+    }
+
+    return( 0 );
+}
+
+#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
+
 #endif /* MBEDTLS_KEY_EXCHANGE_WITH_CERT_ENABLED */
 
 #if defined(MBEDTLS_USE_PSA_CRYPTO) || defined(MBEDTLS_SSL_PROTO_TLS1_3)
@@ -2276,10 +2374,6 @@
                                        const unsigned char *end );
 #endif /* MBEDTLS_SSL_SERVER_NAME_INDICATION */
 
-int mbedtls_ssl_tls13_get_sig_alg_from_pk( mbedtls_ssl_context *ssl,
-                                           mbedtls_pk_context *own_key,
-                                           uint16_t *algorithm );
-
 #if defined(MBEDTLS_SSL_ALPN)
 int mbedtls_ssl_parse_alpn_ext( mbedtls_ssl_context *ssl,
                                 const unsigned char *buf,
diff --git a/library/ssl_tls13_generic.c b/library/ssl_tls13_generic.c
index 893de43..3ab6cc2 100644
--- a/library/ssl_tls13_generic.c
+++ b/library/ssl_tls13_generic.c
@@ -854,120 +854,25 @@
 /*
  * STATE HANDLING: Output Certificate Verify
  */
-int mbedtls_ssl_tls13_get_sig_alg_from_pk( mbedtls_ssl_context *ssl,
-                                           mbedtls_pk_context *own_key,
-                                           uint16_t *algorithm )
+
+static int ssl_tls13_get_sig_alg_from_pk( mbedtls_ssl_context *ssl,
+                                          mbedtls_pk_context *own_key,
+                                          uint16_t *algorithm )
 {
-    mbedtls_pk_type_t sig = mbedtls_ssl_sig_from_pk( own_key );
-    /* Determine the size of the key */
-    size_t own_key_size = mbedtls_pk_get_bitlen( own_key );
+    uint16_t *sig_alg = ssl->handshake->received_sig_algs;
+
     *algorithm = MBEDTLS_TLS1_3_SIG_NONE;
-    ((void) own_key_size);
-
-    switch( sig )
+    for( ; *sig_alg != MBEDTLS_TLS1_3_SIG_NONE ; sig_alg++ )
     {
-#if defined(MBEDTLS_ECDSA_C)
-        case MBEDTLS_SSL_SIG_ECDSA:
-            switch( own_key_size )
-            {
-                case 256:
-                    *algorithm = MBEDTLS_TLS1_3_SIG_ECDSA_SECP256R1_SHA256;
-                    return( 0 );
-                case 384:
-                    *algorithm = MBEDTLS_TLS1_3_SIG_ECDSA_SECP384R1_SHA384;
-                    return( 0 );
-                case 521:
-                    *algorithm = MBEDTLS_TLS1_3_SIG_ECDSA_SECP521R1_SHA512;
-                    return( 0 );
-                default:
-                    MBEDTLS_SSL_DEBUG_MSG( 3,
-                                           ( "unknown key size: %"
-                                             MBEDTLS_PRINTF_SIZET " bits",
-                                             own_key_size ) );
-                    break;
-            }
-            break;
-#endif /* MBEDTLS_ECDSA_C */
-
-#if defined(MBEDTLS_RSA_C)
-        case MBEDTLS_SSL_SIG_RSA:
-#if defined(MBEDTLS_PKCS1_V21)
-#if defined(MBEDTLS_SHA256_C)
-            if( own_key_size <= 2048 &&
-                mbedtls_ssl_sig_alg_is_received( ssl,
-                                    MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA256 ) )
-            {
-                *algorithm = MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA256;
-                return( 0 );
-            }
-            else
-#endif /* MBEDTLS_SHA256_C */
-#if defined(MBEDTLS_SHA384_C)
-            if( own_key_size <= 3072 &&
-                mbedtls_ssl_sig_alg_is_received( ssl,
-                                    MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA384 ) )
-            {
-                *algorithm = MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA384;
-                return( 0 );
-            }
-            else
-#endif /* MBEDTLS_SHA384_C */
-#if defined(MBEDTLS_SHA512_C)
-            if( own_key_size <= 4096 &&
-                mbedtls_ssl_sig_alg_is_received( ssl,
-                                    MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA512 ) )
-            {
-                *algorithm = MBEDTLS_TLS1_3_SIG_RSA_PSS_RSAE_SHA512;
-                return( 0 );
-            }
-            else
-#endif /* MBEDTLS_SHA512_C */
-#endif /* MBEDTLS_PKCS1_V21 */
-#if defined(MBEDTLS_PKCS1_V15)
-#if defined(MBEDTLS_SHA256_C)
-            if( own_key_size <= 2048 &&
-                mbedtls_ssl_sig_alg_is_received( ssl,
-                                    MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA256 ) )
-            {
-                *algorithm = MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA256;
-                return( 0 );
-            }
-            else
-#endif /* MBEDTLS_SHA256_C */
-#if defined(MBEDTLS_SHA384_C)
-            if( own_key_size <= 3072 &&
-                mbedtls_ssl_sig_alg_is_received( ssl,
-                                    MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA384 ) )
-            {
-                *algorithm = MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA384;
-                return( 0 );
-            }
-            else
-#endif /* MBEDTLS_SHA384_C */
-#if defined(MBEDTLS_SHA512_C)
-            if( own_key_size <= 4096 &&
-                mbedtls_ssl_sig_alg_is_received( ssl,
-                                    MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA512 ) )
-            {
-                *algorithm = MBEDTLS_TLS1_3_SIG_RSA_PKCS1_SHA512;
-                return( 0 );
-            }
-            else
-#endif /* MBEDTLS_SHA512_C */
-#endif /* MBEDTLS_PKCS1_V15 */
-            {
-                MBEDTLS_SSL_DEBUG_MSG( 3,
-                                       ( "unknown key size: %"
-                                         MBEDTLS_PRINTF_SIZET " bits",
-                                         own_key_size ) );
-            }
-            break;
-#endif /* MBEDTLS_RSA_C */
-        default:
-            MBEDTLS_SSL_DEBUG_MSG( 1,
-                                   ( "unknown signature type : %u", sig ) );
-            break;
+        if( mbedtls_ssl_sig_alg_is_supported( ssl, *sig_alg) &&
+            mbedtls_ssl_tls13_sig_alg_is_available_for_pk(
+                                              ssl, *sig_alg, own_key ) )
+        {
+            *algorithm = *sig_alg;
+            return( 0 );
+        }
     }
+
     return( -1 );
 }
 
@@ -1024,7 +929,7 @@
      *    opaque signature<0..2^16-1>;
      *  } CertificateVerify;
      */
-    ret = mbedtls_ssl_tls13_get_sig_alg_from_pk( ssl, own_key, &algorithm );
+    ret = ssl_tls13_get_sig_alg_from_pk( ssl, own_key, &algorithm );
     if( ret != 0 || ! mbedtls_ssl_sig_alg_is_received( ssl, algorithm ) )
     {
         MBEDTLS_SSL_DEBUG_MSG( 1,
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index ffbbbcf..0ebad93 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -352,7 +352,6 @@
 {
     mbedtls_ssl_key_cert *key_cert, *key_cert_list;
     const uint16_t *sig_alg = ssl->handshake->received_sig_algs;
-    uint16_t key_sig_alg;
 
 #if defined(MBEDTLS_SSL_SERVER_NAME_INDICATION)
     if( ssl->handshake->sni_key_cert != NULL )
@@ -372,7 +371,6 @@
         for( key_cert = key_cert_list; key_cert != NULL;
              key_cert = key_cert->next )
         {
-            int ret;
             MBEDTLS_SSL_DEBUG_CRT( 3, "certificate (chain) candidate",
                                    key_cert->cert );
 
@@ -391,11 +389,9 @@
                 continue;
             }
 
-            ret = mbedtls_ssl_tls13_get_sig_alg_from_pk(
-                    ssl, &key_cert->cert->pk, &key_sig_alg );
-            if( ret != 0 )
-                continue;
-            if( *sig_alg == key_sig_alg )
+            MBEDTLS_SSL_DEBUG_MSG( 2,("Try get sig alg %04x",*sig_alg));
+            if( mbedtls_ssl_tls13_sig_alg_is_available_for_pk(
+                    ssl, *sig_alg, &key_cert->cert->pk ) )
             {
                 ssl->handshake->key_cert = key_cert;
                 MBEDTLS_SSL_DEBUG_CRT(
@@ -406,6 +402,7 @@
         }
     }
 
+    MBEDTLS_SSL_DEBUG_MSG( 2,("No signature algorithm found"));
     return( -1 );
 }
 #endif /* MBEDTLS_X509_CRT_PARSE_C &&