#2

1 files changed, 101 insertions, 0 deletions

diff --git a/include/hybbx/crypto.h b/include/hybbx/crypto.h
new file mode 100644
index 0000000..5411e5e
--- /dev/null
+++ b/include/hybbx/crypto.h
@@ -0,0 +1,101 @@
+#ifndef HYBBX_CRYPTO_H
+#define HYBBX_CRYPTO_H
+
+#include "hybbx/types.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * HyBBX reversible cryptography.
+ *
+ * Defaults use bundled in-tree sources (tinyaes, monocypher). Backends are
+ * selectable system-wide via `[crypto]` in hybbx.ini when optional OpenSSL or
+ * libsodium support is enabled at build time (see hybbx/crypto_config.h).
+ *
+ * Three modern AEAD schemes:
+ *   1. AES-256-GCM        (NIST, TLS, IPsec)
+ *   2. XChaCha20-Poly1305 (extended-nonce ChaCha, Monocypher)
+ *   3. X25519 + XChaCha20-Poly1305 sealed messages (ECIES-style, Monocypher)
+ *
+ * Password hashing (one-way) remains in hybbx/password.h (SHA-256 / MD5).
+ */
+
+typedef enum hybbx_crypto_alg {
+    HYBBX_CRYPTO_AES_256_GCM = 1,
+    HYBBX_CRYPTO_XCHACHA20_POLY1305 = 2,
+    HYBBX_CRYPTO_X25519_AEAD = 3
+} hybbx_crypto_alg_t;
+
+#define HYBBX_CRYPTO_KEY_SIZE          32
+#define HYBBX_CRYPTO_TAG_SIZE          16
+#define HYBBX_CRYPTO_AES_GCM_NONCE     12
+#define HYBBX_CRYPTO_XCHACHA_NONCE     24
+#define HYBBX_CRYPTO_X25519_PUBLIC_KEY 32
+#define HYBBX_CRYPTO_X25519_SECRET_KEY 32
+/** Sealed blob overhead: ephemeral_pk(32) + nonce(24) + tag(16). */
+#define HYBBX_CRYPTO_X25519_SEAL_OVERHEAD 72
+
+/** Fill @p buf with system random bytes. */
+hybbx_result_t hybbx_crypto_random(uint8_t *buf, size_t len);
+
+/** Human-readable cipher name. */
+const char *hybbx_crypto_alg_name(hybbx_crypto_alg_t alg);
+
+/** Required nonce length for @p alg (0 for X25519 sealed mode). */
+size_t hybbx_crypto_nonce_size(hybbx_crypto_alg_t alg);
+
+/**
+ * Symmetric AEAD encrypt (algorithms 1 and 2).
+ * @p ciphertext length equals @p plaintext_len; authentication tag is separate.
+ */
+hybbx_result_t hybbx_crypto_encrypt(hybbx_crypto_alg_t alg,
+                                    const uint8_t key[HYBBX_CRYPTO_KEY_SIZE],
+                                    const uint8_t *nonce, size_t nonce_len,
+                                    const uint8_t *aad, size_t aad_len,
+                                    const uint8_t *plaintext,
+                                    size_t plaintext_len,
+                                    uint8_t *ciphertext,
+                                    uint8_t tag[HYBBX_CRYPTO_TAG_SIZE]);
+
+/** Symmetric AEAD decrypt; returns HYBBX_ERR_DENIED when the tag is invalid. */
+hybbx_result_t hybbx_crypto_decrypt(hybbx_crypto_alg_t alg,
+                                    const uint8_t key[HYBBX_CRYPTO_KEY_SIZE],
+                                    const uint8_t *nonce, size_t nonce_len,
+                                    const uint8_t *aad, size_t aad_len,
+                                    const uint8_t *ciphertext,
+                                    size_t ciphertext_len,
+                                    uint8_t *plaintext,
+                                    const uint8_t tag[HYBBX_CRYPTO_TAG_SIZE]);
+
+/** Generate an X25519 key pair (Montgomery curve, RFC 7748). */
+hybbx_result_t hybbx_crypto_x25519_keypair(
+    uint8_t public_key[HYBBX_CRYPTO_X25519_PUBLIC_KEY],
+    uint8_t secret_key[HYBBX_CRYPTO_X25519_SECRET_KEY]);
+
+/**
+ * Asymmetric seal for @p recipient_pk.
+ * Output: ephemeral_pk || nonce || ciphertext || tag.
+ */
+hybbx_result_t hybbx_crypto_x25519_seal(
+    const uint8_t recipient_pk[HYBBX_CRYPTO_X25519_PUBLIC_KEY],
+    const uint8_t *aad, size_t aad_len,
+    const uint8_t *plaintext, size_t plaintext_len,
+    uint8_t *sealed, size_t *sealed_len, size_t sealed_cap);
+
+/** Open a sealed message with @p recipient_sk. */
+hybbx_result_t hybbx_crypto_x25519_open(
+    const uint8_t recipient_sk[HYBBX_CRYPTO_X25519_SECRET_KEY],
+    const uint8_t *aad, size_t aad_len,
+    const uint8_t *sealed, size_t sealed_len,
+    uint8_t *plaintext, size_t *plaintext_len, size_t plaintext_cap);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* HYBBX_CRYPTO_H */