feat: add Jasmin assembly integration for crypto acceleration

- Integrated `zupt_mac_verify_ct` in `zupt_decrypt_buffer()` to replace C XOR loop for HMAC-SHA256
- Integrated `zupt_ct_select_32` in `zupt_mlkem768_decaps()` to replace C `cmov()` for FO transformation
- Added `include/zupt_jasmin.h` with extern declarations and ABI docs
- Added `#ifdef ZUPT_USE_JASMIN` guards with clean C fallbacks in `zupt_crypto.c` and `zupt_mlkem.c`
- Makefile now auto-detects `jasmin/*.s`, assembles and links with `-DZUPT_USE_JASMIN`

Closes #3

include/zupt_mlkem.h

@@ -0,0 +1,65 @@
+/*
+ * Zupt — Backup-oriented compression with AES-256 encryption
+ * Copyright (c) 2026 Cristian Cezar Moisés
+ * SPDX-License-Identifier: MIT
+ *
+ * ML-KEM-768 (FIPS 203, formerly CRYSTALS-Kyber).
+ * Post-quantum key encapsulation mechanism.
+ *
+ * Parameters (ML-KEM-768):
+ *   k = 3, η₁ = 2, η₂ = 2, d_u = 10, d_v = 4
+ *   Public key:  1184 bytes
+ *   Secret key:  2400 bytes
+ *   Ciphertext:  1088 bytes
+ *   Shared secret: 32 bytes
+ *
+ * SECURITY NOTE: This implementation must undergo independent review
+ * before deployment in high-assurance contexts. It targets correctness
+ * against NIST test vectors and constant-time operation.
+ */
+#ifndef ZUPT_MLKEM_H
+#define ZUPT_MLKEM_H
+
+#include <stdint.h>
+
+#define MLKEM_K     3
+#define MLKEM_N     256
+#define MLKEM_Q     3329
+#define MLKEM_ETA1  2
+#define MLKEM_ETA2  2
+#define MLKEM_DU    10
+#define MLKEM_DV    4
+
+#define MLKEM_PUBLICKEYBYTES    1184
+#define MLKEM_SECRETKEYBYTES    2400
+#define MLKEM_CIPHERTEXTBYTES   1088
+#define MLKEM_SSBYTES           32
+
+/* KeyGen: generate public/secret keypair.
+ * pk: output public key (1184 bytes)
+ * sk: output secret key (2400 bytes)
+ * Returns 0 on success. */
+int zupt_mlkem768_keygen(uint8_t pk[MLKEM_PUBLICKEYBYTES],
+                          uint8_t sk[MLKEM_SECRETKEYBYTES]);
+
+/* Encapsulate: produce ciphertext and shared secret from public key.
+ * ct: output ciphertext (1088 bytes)
+ * ss: output shared secret (32 bytes)
+ * pk: input public key (1184 bytes)
+ * Returns 0 on success. */
+int zupt_mlkem768_encaps(uint8_t ct[MLKEM_CIPHERTEXTBYTES],
+                          uint8_t ss[MLKEM_SSBYTES],
+                          const uint8_t pk[MLKEM_PUBLICKEYBYTES]);
+
+/* Decapsulate: recover shared secret from ciphertext and secret key.
+ * ss: output shared secret (32 bytes)
+ * ct: input ciphertext (1088 bytes)
+ * sk: input secret key (2400 bytes)
+ * Returns 0 on success.
+ * CT-REQUIRED: Implicit rejection — invalid ciphertext produces a
+ * pseudorandom shared secret (no distinguishable failure). */
+int zupt_mlkem768_decaps(uint8_t ss[MLKEM_SSBYTES],
+                          const uint8_t ct[MLKEM_CIPHERTEXTBYTES],
+                          const uint8_t sk[MLKEM_SECRETKEYBYTES]);
+
+#endif