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diff --git a/src/crypto/aes_gcm.h b/src/crypto/aes_gcm.h
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+#ifndef AES_GCM_H
+#define AES_GCM_H
+
+#include <basic/basic.h>
+
+// Note: Aes-256
+// - https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
+// - DANGER: max. 2^32 invocations!!!
+
+// Note: Aes Key
+// - for aes-256 always 32 bytes
+
+// Note: Initialization Vector
+// - for aes-256 is always 12 bytes for optimal usage
+// - https://www.rfc-editor.org/rfc/rfc5288#section-3
+
+// Note: Authentication Tag
+// - is sent with every message
+// - is calculated after whole message is encrypted
+// - len is preferred 16 bytes for max security
+
+
+typedef struct {
+    u8 buff[32];
+} AesGcmKey;
+
+typedef struct {
+    u8 salt[8];
+    u8 counter[4];
+} AesGcmIv;
+
+typedef struct {
+    u32 payload_size;
+    u8 tag[16];
+} AesGcmHeader;
+
+
+b32  aes_gcm_key_init_random(AesGcmKey *key);
+
+b32  aes_gcm_iv_init(AesGcmIv *iv);
+void aes_gcm_iv_advance(AesGcmIv *iv);
+
+b32 aes_gcm_encrypt(AesGcmKey *key, AesGcmIv *iv,
+                    u8 *ciphertext, u8 *plaintext, i32 plaintext_len,
+                    u8 *tag_out, i32 tag_out_len);
+b32 aes_gcm_decrypt(AesGcmKey *key, AesGcmIv *iv,
+                    u8 *plaintext, u8 *ciphertext, i32 ciphertext_len,
+                    u8 *tag, i32 tag_len);
+
+
+#endif // AES_GCM_H