diff --git a/library/asn1write.c b/library/asn1write.c
index 69b61b2..d916fcb 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -232,10 +232,6 @@
     int ret;
     size_t len = 0;
 
-    // TODO negative values and values larger than 128
-    // DER format assumes 2s complement for numbers, so the leftmost bit
-    // should be 0 for positive numbers and 1 for negative numbers.
-    //
     if( *p - start < 1 )
         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
 
@@ -257,34 +253,37 @@
     return( (int) len );
 }
 
-int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start,
-                                 const char *text, size_t text_len )
+int mbedtls_asn1_write_any_string( unsigned char **p, unsigned char *start, int tag,
+    const char *text, size_t text_len )
 {
     int ret;
     size_t len = 0;
 
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
-                  (const unsigned char *) text, text_len ) );
+        (const unsigned char *) text, text_len ) );
 
     MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
-    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_PRINTABLE_STRING ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, tag ) );
 
     return( (int) len );
 }
 
+int mbedtls_asn1_write_utf8_string( unsigned char **p, unsigned char *start,
+    const char *text, size_t text_len )
+{
+    return( mbedtls_asn1_write_any_string(p, start, MBEDTLS_ASN1_UTF8_STRING, text, text_len) );
+}
+
+int mbedtls_asn1_write_printable_string( unsigned char **p, unsigned char *start,
+                                 const char *text, size_t text_len )
+{
+    return( mbedtls_asn1_write_any_string(p, start, MBEDTLS_ASN1_PRINTABLE_STRING, text, text_len) );
+}
+
 int mbedtls_asn1_write_ia5_string( unsigned char **p, unsigned char *start,
                            const char *text, size_t text_len )
 {
-    int ret;
-    size_t len = 0;
-
-    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_raw_buffer( p, start,
-                  (const unsigned char *) text, text_len ) );
-
-    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
-    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_IA5_STRING ) );
-
-    return( (int) len );
+    return( mbedtls_asn1_write_any_string(p, start, MBEDTLS_ASN1_IA5_STRING, text, text_len) );
 }
 
 int mbedtls_asn1_write_bitstring( unsigned char **p, unsigned char *start,