ohhhhhhhhhhh (exclude linux-extra-rootfs.img build artifact)

CODE/UTSM/crypto/stream.c

@@ -1,19 +1,26 @@
+/* stream.c — 64B cache line 流加密（Phase 9：ChaCha20）
+ *
+ * ct = pt XOR ChaCha20_block(segment_key, nonce=tweak, counter=0)
+ * 1 block = 1 line；加密解密同函数（XOR 流）。
+ * nonce 唯一性：(segment_key 全局唯一) × (line_index 段内唯一)，
+ * key_epoch 混入 key 派生，故同 (key,nonce) 只生成一次 keystream。
+ */
+
 #include <utsm/crypto.h>
+#include <utsm/blake2b.h>
 #include <utsm/config.h>
 
-static u64 next_stream_word(u64 x) {
-    x ^= x << 13;
-    x ^= x >> 7;
-    x ^= x << 17;
-    return x;
-}
-
 void utsm_crypt_line(const utsm_key_material *key, u64 tweak, const u8 *in, u8 *out) {
-    u64 state = key->words[0] ^ key->words[1] ^ key->words[2] ^ key->words[3] ^ tweak;
-    for (u64 i = 0; i < UTSM_CACHE_LINE_SIZE; i += 8) {
-        state = next_stream_word(state + i + 0xa5a5a5a5a5a5a5a5ULL);
-        for (u64 j = 0; j < 8; j++) {
-            out[i + j] = in[i + j] ^ (u8)(state >> (j * 8));
-        }
+    u32 kw[8];
+    for (int i = 0; i < 4; i++) {
+        kw[2 * i] = (u32)(key->words[i] & 0xFFFFFFFFu);
+        kw[2 * i + 1] = (u32)(key->words[i] >> 32);
+    }
+
+    u8 ks[64];
+    utsm_chacha20_block(kw, tweak, 0, ks);
+
+    for (u32 i = 0; i < UTSM_CACHE_LINE_SIZE; i++) {
+        out[i] = in[i] ^ ks[i];
     }
 }