diff --git a/programs/ssl/ssl_client2.c b/programs/ssl/ssl_client2.c
index 486b6a6..2e8e105 100644
--- a/programs/ssl/ssl_client2.c
+++ b/programs/ssl/ssl_client2.c
@@ -74,6 +74,8 @@
 #include "mbedtls/psa_util.h"
 #endif
 
+#include <test/helpers.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -1016,45 +1018,6 @@
     return( 0 );
 }
 
-/* Unhexify `hex` into `dst`. `dst` must have
- * size at least `strlen( hex ) / 2`. */
-int unhexify( char const *hex, unsigned char *dst )
-{
-    unsigned char c;
-    size_t j;
-    size_t len = strlen( hex );
-
-    if( len % 2 != 0 )
-        return( -1 );
-
-    for( j = 0; j < len; j += 2 )
-    {
-        c = hex[j];
-        if( c >= '0' && c <= '9' )
-            c -= '0';
-        else if( c >= 'a' && c <= 'f' )
-            c -= 'a' - 10;
-        else if( c >= 'A' && c <= 'F' )
-            c -= 'A' - 10;
-        else
-            return( -1 );
-        dst[ j / 2 ] = c << 4;
-
-        c = hex[j + 1];
-        if( c >= '0' && c <= '9' )
-            c -= '0';
-        else if( c >= 'a' && c <= 'f' )
-            c -= 'a' - 10;
-        else if( c >= 'A' && c <= 'F' )
-            c -= 'A' - 10;
-        else
-            return( -1 );
-        dst[ j / 2 ] |= c;
-    }
-
-    return( 0 );
-}
-
 #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
 int report_cid_usage( mbedtls_ssl_context *ssl,
                       const char *additional_description )
@@ -1785,16 +1748,10 @@
      */
     if( strlen( opt.psk ) )
     {
-        psk_len = strlen( opt.psk ) / 2;
-        if( psk_len > sizeof( psk ) )
+        if( mbedtls_test_unhexify( psk, sizeof( psk ),
+                                   opt.psk, &psk_len ) != 0 )
         {
-            mbedtls_printf( "pre-shared key too long\n" );
-            goto exit;
-        }
-
-        if( unhexify( opt.psk, psk ) != 0 )
-        {
-            mbedtls_printf( "pre-shared key not valid hex\n" );
+            mbedtls_printf( "pre-shared key not valid\n" );
             goto exit;
         }
     }
@@ -1896,16 +1853,10 @@
     }
 
 #if defined(MBEDTLS_SSL_DTLS_CONNECTION_ID)
-    cid_len = strlen( opt.cid_val ) / 2;
-    if( cid_len > sizeof( cid ) )
+    if( mbedtls_test_unhexify( cid, sizeof( cid ),
+                               opt.cid_val, &cid_len ) != 0 )
     {
-        mbedtls_printf( "CID too long\n" );
-        goto exit;
-    }
-
-    if( unhexify( opt.cid_val, cid ) != 0 )
-    {
-        mbedtls_printf( "CID not valid hex\n" );
+        mbedtls_printf( "CID not valid\n" );
         goto exit;
     }
 
@@ -1916,16 +1867,10 @@
     if( opt.cid_val_renego == DFL_CID_VALUE_RENEGO )
         opt.cid_val_renego = opt.cid_val;
 
-    cid_renego_len = strlen( opt.cid_val_renego ) / 2;
-    if( cid_renego_len > sizeof( cid_renego ) )
+    if( mbedtls_test_unhexify( cid_renego, sizeof( cid_renego ),
+                               opt.cid_val_renego, &cid_renego_len ) != 0 )
     {
-        mbedtls_printf( "CID too long\n" );
-        goto exit;
-    }
-
-    if( unhexify( opt.cid_val_renego, cid_renego ) != 0 )
-    {
-        mbedtls_printf( "CID not valid hex\n" );
+        mbedtls_printf( "CID not valid\n" );
         goto exit;
     }
 #endif /* MBEDTLS_SSL_DTLS_CONNECTION_ID */