Branch version ready for testing with nRF52

src/crypto/vble_aes.h

@@ -0,0 +1,45 @@
+/**
+ * Minimal AES-128 CTR-mode implementation for VictronBLE.
+ *
+ * Trimmed (CTR only, AES-128 only) and symbol-prefixed adaptation of
+ * kokke/tiny-AES-c (public domain / Unlicense), verified against the test
+ * vectors in NIST SP 800-38A. Bundled so the library has no external crypto
+ * dependency and builds identically on ESP32, nRF52 and any other target.
+ *
+ * Counter increment matches mbedTLS mbedtls_aes_crypt_ctr (increments the
+ * 128-bit counter from the least-significant byte), so output is byte-identical
+ * to the previous ESP32 mbedTLS-based decryption.
+ */
+#ifndef VBLE_AES_H_
+#define VBLE_AES_H_
+
+#include <stdint.h>
+#include <stddef.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define VBLE_AES_BLOCKLEN 16   // AES block length in bytes (128-bit)
+#define VBLE_AES_KEYLEN   16   // AES-128 key length in bytes
+#define VBLE_AES_KEYEXPSIZE 176
+
+struct vble_aes_ctx {
+    uint8_t RoundKey[VBLE_AES_KEYEXPSIZE];
+    uint8_t Iv[VBLE_AES_BLOCKLEN];
+};
+
+// Initialise context with a 16-byte key and 16-byte IV (counter).
+void vble_aes_init_ctx_iv(struct vble_aes_ctx* ctx,
+                          const uint8_t* key, const uint8_t* iv);
+
+// CTR-mode keystream XOR. Symmetric: same call encrypts and decrypts.
+// Operates in place on `buf` for `length` bytes (length need not be a
+// multiple of the block size).
+void vble_aes_ctr_xcrypt(struct vble_aes_ctx* ctx, uint8_t* buf, size_t length);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif // VBLE_AES_H_