Add _init() and _free() for cipher modules
diff --git a/library/blowfish.c b/library/blowfish.c
index d8b0c36..87396dc 100644
--- a/library/blowfish.c
+++ b/library/blowfish.c
@@ -41,6 +41,11 @@
 
 #if !defined(POLARSSL_BLOWFISH_ALT)
 
+/* Implementation that should never be optimized out by the compiler */
+static void polarssl_zeroize( void *v, size_t n ) {
+    volatile unsigned char *p = v; while( n-- ) *p++ = 0;
+}
+
 /*
  * 32-bit integer manipulation macros (big endian)
  */
@@ -152,6 +157,19 @@
     *xr = Xr;
 }
 
+void blowfish_init( blowfish_context *ctx )
+{
+    memset( ctx, 0, sizeof( blowfish_context ) );
+}
+
+void blowfish_free( blowfish_context *ctx )
+{
+    if( ctx == NULL )
+        return;
+
+    polarssl_zeroize( ctx, sizeof( blowfish_context ) );
+}
+
 /*
  * Blowfish key schedule
  */