X-Git-Url: https://jxself.org/git/?a=blobdiff_plain;f=tftweakapi.c;fp=tftweakapi.c;h=5f68fe591c6a2fea22ddc8713f01e8a21219505d;hb=f402e6aa2dd18138ec26e9bfb340dae294637aec;hp=0000000000000000000000000000000000000000;hpb=0b911d4a813fe164d62ef6ef132c5a4f9a441d57;p=tfcrypt.git

diff --git a/tftweakapi.c b/tftweakapi.c
new file mode 100644
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];
+}