Replace ugly tweak size computation with explicit tweak clean API.

[tfcrypt.git] / tftweakapi.c

diff --git a/tftweakapi.c b/tftweakapi.c
new file mode 100644 (file)
index 0000000..5f68fe5
--- /dev/null
+++ b/tftweakapi.c
@@ -0,0 +1,23 @@
+#include <string.h>
+#include "tfdef.h"
+#include "tfcore.h"
+
+void tf_tweak_set(void *key, const void *tweak)
+{
+       TF_UNIT_TYPE *ukey = key;
+       TF_UNIT_TYPE *twe = ukey+TF_TWEAK_WORD1;
+       TF_UNIT_TYPE c = THREEFISH_CONST;
+       size_t x;
+
+       for (x = 0; x < TF_NR_BLOCK_UNITS; x++) c ^= ukey[x];
+       ukey[x] = c;
+
+       if (!tweak) {
+               memset(twe, 0, (TF_NR_TWEAK_UNITS+1)*TF_SIZE_UNIT);
+               return;
+       }
+
+       memcpy(twe, tweak, TF_NR_TWEAK_UNITS*TF_SIZE_UNIT);
+       data_to_words(twe, TF_NR_TWEAK_UNITS*TF_SIZE_UNIT);
+       ukey[TF_TWEAK_WORD3] = ukey[TF_TWEAK_WORD1] ^ ukey[TF_TWEAK_WORD2];
+}