diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index 687a349..e8bea07 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -491,10 +491,6 @@
 /** \brief Encoding of permitted usage on a key. */
 typedef uint32_t psa_key_usage_t;
 
-/** An invalid key usage value.
- * */
-#define PSA_KEY_USAGE_NONE                      ((psa_key_usage_t)0x00000000)
-
 /** Whether the key may be exported.
  *
  * A public key or the public part of a key pair may always be exported
diff --git a/include/psa/crypto_struct.h b/include/psa/crypto_struct.h
index 8987840..eba4862 100644
--- a/include/psa/crypto_struct.h
+++ b/include/psa/crypto_struct.h
@@ -82,6 +82,8 @@
     int iv_required : 1;
     int iv_set : 1;
     int has_input : 1;
+    int key_usage_sign : 1;
+    int key_usage_verify : 1;
     uint8_t mac_size;
     union
     {
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 9fd0a61..2391006 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -986,6 +986,12 @@
         return( status );
     slot = &global_data.key_slots[key];
 
+    if ( ( slot->policy.usage & PSA_KEY_USAGE_SIGN ) != 0 )
+        operation->key_usage_sign = 1;
+
+    if ( ( slot->policy.usage & PSA_KEY_USAGE_VERIFY ) != 0 )
+        operation->key_usage_verify = 1;
+
     if( ! PSA_ALG_IS_HMAC( alg ) )
     {
         cipher_info = mbedtls_cipher_info_from_psa( alg, key_type, key_bits );
@@ -1084,7 +1090,7 @@
     return( mbedtls_to_psa_error( ret ) );
 }
 
-psa_status_t psa_mac_finish( psa_mac_operation_t *operation,
+static psa_status_t psa_mac_finish_internal( psa_mac_operation_t *operation,
                              uint8_t *mac,
                              size_t mac_size,
                              size_t *mac_length )
@@ -1136,6 +1142,17 @@
     }
 }
 
+psa_status_t psa_mac_finish( psa_mac_operation_t *operation,
+                             uint8_t *mac,
+                             size_t mac_size,
+                             size_t *mac_length )
+{
+    if( !( operation->key_usage_sign ) )
+        return( PSA_ERROR_NOT_PERMITTED );
+
+    return( psa_mac_finish_internal(operation, mac, mac_size, mac_length ) );
+}
+
 #define MBEDTLS_PSA_MAC_MAX_SIZE                       \
     ( MBEDTLS_MD_MAX_SIZE > MBEDTLS_MAX_BLOCK_LENGTH ? \
       MBEDTLS_MD_MAX_SIZE :                            \
@@ -1146,9 +1163,14 @@
 {
     uint8_t actual_mac[MBEDTLS_PSA_MAC_MAX_SIZE];
     size_t actual_mac_length;
-    psa_status_t status = psa_mac_finish( operation,
-                                          actual_mac, sizeof( actual_mac ),
-                                          &actual_mac_length );
+    psa_status_t status;
+
+    if( !( operation->key_usage_verify ) )
+        return( PSA_ERROR_NOT_PERMITTED );
+
+    status = psa_mac_finish_internal( operation,
+                                      actual_mac, sizeof( actual_mac ),
+                                      &actual_mac_length );
     if( status != PSA_SUCCESS )
         return( status );
     if( actual_mac_length != mac_length )
@@ -1272,7 +1294,7 @@
 
 void psa_key_policy_init(psa_key_policy_t *policy)
 {
-    mbedtls_zeroize( policy, sizeof( policy ) );
+    memset( policy, 0, sizeof( psa_key_policy_t ) );
 }
 
 void psa_key_policy_set_usage(psa_key_policy_t *policy,
@@ -1285,19 +1307,18 @@
 
 psa_key_usage_t psa_key_policy_get_usage(psa_key_policy_t *policy)
 {
-    return policy->usage;
+    return( policy->usage );
 }
 
 psa_algorithm_t psa_key_policy_get_algorithm(psa_key_policy_t *policy)
 {
-    return policy->alg;
+    return( policy->alg );
 }
 
 psa_status_t psa_set_key_policy(psa_key_slot_t key,
                                 const psa_key_policy_t *policy)
 {
     key_slot_t *slot;
-    psa_key_usage_t usage = PSA_KEY_USAGE_NONE;
 
     if( key == 0 || key > MBEDTLS_PSA_KEY_SLOT_COUNT || policy == NULL )
         return( PSA_ERROR_INVALID_ARGUMENT );
@@ -1306,20 +1327,12 @@
     if( slot->type != PSA_KEY_TYPE_NONE )
         return( PSA_ERROR_OCCUPIED_SLOT );
 
-    usage |= policy->usage & PSA_KEY_USAGE_EXPORT;
-    usage |= policy->usage & PSA_KEY_USAGE_ENCRYPT;
-    usage |= policy->usage & PSA_KEY_USAGE_DECRYPT;
-    usage |= policy->usage & PSA_KEY_USAGE_SIGN;
-    usage |= policy->usage & PSA_KEY_USAGE_VERIFY;
-
-    if( usage == PSA_KEY_USAGE_NONE )
-    {
+    if( ( policy->usage & ~( PSA_KEY_USAGE_EXPORT | PSA_KEY_USAGE_ENCRYPT 
+                        | PSA_KEY_USAGE_DECRYPT | PSA_KEY_USAGE_SIGN 
+                        | PSA_KEY_USAGE_VERIFY ) ) != 0 )
         return( PSA_ERROR_INVALID_KEY_POLICY );
-    }
 
-    //TODO: is there any check over the algorithm before setting the policy?
-    slot->policy.usage = policy->usage;
-    slot->policy.alg = policy->alg;
+    slot->policy = *policy;
 
     return( PSA_SUCCESS );
 }
@@ -1336,8 +1349,7 @@
     if( slot->type == PSA_KEY_TYPE_NONE )
         return( PSA_ERROR_EMPTY_SLOT );
     
-    policy->usage = slot->policy.usage;
-    policy->alg = slot->policy.alg;
+    *policy = slot->policy;
 
     return( PSA_SUCCESS );
 }
diff --git a/tests/suites/test_suite_psa_crypto.data b/tests/suites/test_suite_psa_crypto.data
index 2c2be21..da01e23 100644
--- a/tests/suites/test_suite_psa_crypto.data
+++ b/tests/suites/test_suite_psa_crypto.data
@@ -87,8 +87,8 @@
 PSA Key Policy set and get
 key_policy:PSA_KEY_USAGE_ENCRYPT:PSA_ALG_CBC_BASE
 
-PSA Key Policy enforcment - export
+PSA Key Policy enforcement - export
 key_policy_fail:PSA_KEY_USAGE_EXPORT:PSA_ALG_RSA_PKCS1V15_RAW:PSA_ERROR_NOT_PERMITTED:"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"
 
-PSA Key Policy enforcment - sign
-key_policy_fail:PSA_KEY_USAGE_SIGN:PSA_ALG_CBC_BASE:PSA_ERROR_NOT_PERMITTED:""
+PSA Key Policy enforcement - sign
+key_policy_fail:PSA_KEY_USAGE_SIGN:PSA_ALG_RSA_PKCS1V15_RAW:PSA_ERROR_NOT_PERMITTED:"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"
diff --git a/tests/suites/test_suite_psa_crypto.function b/tests/suites/test_suite_psa_crypto.function
index b0cfe20..bda2e7c 100644
--- a/tests/suites/test_suite_psa_crypto.function
+++ b/tests/suites/test_suite_psa_crypto.function
@@ -221,6 +221,7 @@
     unsigned char *expected_mac = NULL;
     size_t expected_mac_size;
     psa_mac_operation_t operation;
+    psa_key_policy_t policy;
 
     key = unhexify_alloc( key_hex, &key_size );
     TEST_ASSERT( key != NULL );
@@ -236,6 +237,12 @@
 
     TEST_ASSERT( psa_crypto_init( ) == PSA_SUCCESS );
 
+    psa_key_policy_init( &policy );
+
+    psa_key_policy_set_usage( &policy, PSA_KEY_USAGE_VERIFY, alg_arg );
+
+    TEST_ASSERT( psa_set_key_policy( key_slot, &policy ) == PSA_SUCCESS );
+
     TEST_ASSERT( psa_import_key( key_slot, key_type,
                                  key, key_size ) == PSA_SUCCESS );
     // TODO: support IV
@@ -427,7 +434,6 @@
 void key_policy_fail( int usage_arg, int alg_arg, int expected_status, char *key_hex )
 {
     int key_slot = 1;
-    psa_key_type_t key_type = PSA_KEY_TYPE_AES;
     unsigned char key[32] = {0};
     unsigned char* keypair = NULL;
     size_t key_size = 0;
@@ -445,27 +451,22 @@
 
     TEST_ASSERT( psa_set_key_policy( key_slot, &policy ) == PSA_SUCCESS );
 
-    switch( usage_arg )
+    if( usage_arg & PSA_KEY_USAGE_EXPORT )
     {
-        case PSA_KEY_USAGE_EXPORT:
-            keypair = unhexify_alloc( key_hex, &key_size );
-            TEST_ASSERT( keypair != NULL );
-            key_type = PSA_KEY_TYPE_RSA_KEYPAIR;
-            TEST_ASSERT( psa_import_key( key_slot, key_type,
-                                 keypair, key_size ) == PSA_SUCCESS );
-            actual_status = psa_asymmetric_sign( key_slot, 
-                            ( psa_algorithm_t )alg_arg, NULL, 0, NULL, 0, 
-                            NULL, 0, &signature_length );
-            break;
-        
-        case PSA_KEY_USAGE_SIGN:
-            key_type = PSA_KEY_TYPE_AES;
-            TEST_ASSERT( psa_import_key( key_slot, key_type,
-                                 key, sizeof( key ) ) == PSA_SUCCESS );
-            actual_status = psa_export_key( key_slot, NULL, 0, NULL );
-            break;
-        default:
-            break;
+        keypair = unhexify_alloc( key_hex, &key_size );
+        TEST_ASSERT( keypair != NULL );
+        TEST_ASSERT( psa_import_key( key_slot, PSA_KEY_TYPE_RSA_KEYPAIR,
+                                keypair, key_size ) == PSA_SUCCESS );
+        actual_status = psa_asymmetric_sign( key_slot, 
+                        ( psa_algorithm_t )alg_arg, NULL, 0, NULL, 0, 
+                        NULL, 0, &signature_length );
+    }
+    
+    if( usage_arg & PSA_KEY_USAGE_SIGN )
+    {
+        TEST_ASSERT( psa_import_key( key_slot, PSA_KEY_TYPE_RSA_KEYPAIR,
+                                key, sizeof( key ) ) == PSA_SUCCESS );
+        actual_status = psa_export_key( key_slot, NULL, 0, NULL );
     }
 
     TEST_ASSERT( actual_status == expected_status );