diff --git a/library/asn1write.c b/library/asn1write.c
index b1d6839..fc85bf9 100644
--- a/library/asn1write.c
+++ b/library/asn1write.c
@@ -216,9 +216,9 @@
 
     return( len );
 }
-    
+
 int asn1_write_ia5_string( unsigned char **p, unsigned char *start,
-                          char *text )
+                           char *text )
 {
     int ret;
     size_t len = 0;
@@ -238,6 +238,51 @@
 
     return( len );
 }
-    
+
+int asn1_write_bitstring( unsigned char **p, unsigned char *start,
+                          const unsigned char *buf, size_t bits )
+{
+    int ret;
+    size_t len = 0, size;
+
+    size = ( bits / 8 ) + ( ( bits % 8 ) ? 1 : 0 );
+
+    // Calculate byte length
+    //
+    if( *p - start < (int) size + 1 )
+        return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
+
+    len = size + 1;
+    (*p) -= size;
+    memcpy( *p, buf, size );
+
+    // Write unused bits
+    //
+    *--(*p) = size * 8 - bits;
+
+    ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_BIT_STRING ) );
+
+    return( len );
+}
+
+int asn1_write_octet_string( unsigned char **p, unsigned char *start,
+                             const unsigned char *buf, size_t size )
+{
+    int ret;
+    size_t len = 0;
+
+    if( *p - start < (int) size + 1 )
+        return( POLARSSL_ERR_ASN1_BUF_TOO_SMALL );
+
+    len = size;
+    (*p) -= len;
+    memcpy( *p, buf, len );
+
+    ASN1_CHK_ADD( len, asn1_write_len( p, start, len ) );
+    ASN1_CHK_ADD( len, asn1_write_tag( p, start, ASN1_OCTET_STRING ) );
+
+    return( len );
+}
 
 #endif