diff --git a/tests/suites/test_suite_gcm.function b/tests/suites/test_suite_gcm.function
index c0e799c..b3d212a 100644
--- a/tests/suites/test_suite_gcm.function
+++ b/tests/suites/test_suite_gcm.function
@@ -9,41 +9,23 @@
 
 /* BEGIN_CASE */
 void gcm_bad_parameters( int cipher_id, int direction,
-                         char *hex_key_string, char *hex_src_string,
-                         char *hex_iv_string, char *hex_add_string,
+                         HexParam_t *key_str, HexParam_t *src_str,
+                         HexParam_t *iv_str, HexParam_t *add_str,
                          int tag_len_bits, int gcm_result )
 {
-    unsigned char key_str[128];
-    unsigned char src_str[128];
-    unsigned char dst_str[257];
-    unsigned char iv_str[128];
-    unsigned char add_str[128];
-    unsigned char tag_str[128];
     unsigned char output[128];
     unsigned char tag_output[16];
     mbedtls_gcm_context ctx;
-    unsigned int key_len;
-    size_t pt_len, iv_len, add_len, tag_len = tag_len_bits / 8;
+    size_t tag_len = tag_len_bits / 8;
 
     mbedtls_gcm_init( &ctx );
 
-    memset( key_str, 0x00, sizeof( key_str ) );
-    memset( src_str, 0x00, sizeof( src_str ) );
-    memset( dst_str, 0x00, sizeof( dst_str ) );
-    memset( iv_str, 0x00, sizeof( iv_str ) );
-    memset( add_str, 0x00, sizeof( add_str ) );
-    memset( tag_str, 0x00, sizeof( tag_str ) );
     memset( output, 0x00, sizeof( output ) );
     memset( tag_output, 0x00, sizeof( tag_output ) );
 
-    key_len = unhexify( key_str, hex_key_string );
-    pt_len = unhexify( src_str, hex_src_string );
-    iv_len = unhexify( iv_str, hex_iv_string );
-    add_len = unhexify( add_str, hex_add_string );
-
-    TEST_ASSERT( mbedtls_gcm_setkey( &ctx, cipher_id, key_str, key_len * 8 ) == 0 );
-    TEST_ASSERT( mbedtls_gcm_crypt_and_tag( &ctx, direction, pt_len, iv_str, iv_len,
-                 add_str, add_len, src_str, output, tag_len, tag_output ) == gcm_result );
+    TEST_ASSERT( mbedtls_gcm_setkey( &ctx, cipher_id, key_str->x, key_str->len * 8 ) == 0 );
+    TEST_ASSERT( mbedtls_gcm_crypt_and_tag( &ctx, direction, src_str->len, iv_str->x, iv_str->len,
+                 add_str->x, add_str->len, src_str->x, output, tag_len, tag_output ) == gcm_result );
 
 exit:
     mbedtls_gcm_free( &ctx );