protection improvement (1): different S2K for PW1 and Reset-code

src/sha256.c

@@ -194,6 +194,7 @@ sha256_finish (sha256_context *ctx, unsigned char output[32])
 
   bswap32_buf (ctx->state, SHA256_DIGEST_SIZE >> 2);
   memcpy (output, ctx->state, SHA256_DIGEST_SIZE);
+  memset (&ctx, 0, sizeof (sha256_context));
 }
 
 const uint32_t initial_state[8] =
@@ -218,6 +219,4 @@ sha256 (const unsigned char *input, unsigned int ilen,
   sha256_start (&ctx);
   sha256_update (&ctx, input, ilen);
   sha256_finish (&ctx, output);
-
-  memset (&ctx, 0, sizeof (sha256_context));
 }