diff --git a/lib/include/chiaki/gkcrypt.h b/lib/include/chiaki/gkcrypt.h
index ff9ee5b..43ff4c8 100644
--- a/lib/include/chiaki/gkcrypt.h
+++ b/lib/include/chiaki/gkcrypt.h
@@ -42,6 +42,8 @@ struct chiaki_session_t;
 
 CHIAKI_EXPORT ChiakiErrorCode chiaki_gkcrypt_init(ChiakiGKCrypt *gkcrypt, struct chiaki_session_t *session, size_t key_buf_blocks, uint8_t index, uint8_t *handshake_key, uint8_t *ecdh_secret);
 CHIAKI_EXPORT void chiaki_gkcrypt_fini(ChiakiGKCrypt *gkcrypt);
+CHIAKI_EXPORT ChiakiErrorCode chiaki_gkcrypt_decrypt(ChiakiGKCrypt *gkcrypt, size_t key_pos, uint8_t *buf, size_t buf_size);
+static inline ChiakiErrorCode chiaki_gkcrypt_encrypt(ChiakiGKCrypt *gkcrypt, size_t key_pos, uint8_t *buf, size_t buf_size) { return chiaki_gkcrypt_decrypt(gkcrypt, key_pos, buf, buf_size); }
 
 #ifdef __cplusplus
 }
diff --git a/lib/include/chiaki/nagare.h b/lib/include/chiaki/nagare.h
index c056fb1..86af8bd 100644
--- a/lib/include/chiaki/nagare.h
+++ b/lib/include/chiaki/nagare.h
@@ -21,6 +21,7 @@
 #include "mirai.h"
 #include "takion.h"
 #include "log.h"
+#include "ecdh.h"
 
 #include <stdbool.h>
 
@@ -34,6 +35,7 @@ typedef struct chiaki_nagare_t
 	ChiakiLog *log;
 	ChiakiTakion takion;
 	ChiakiMirai bang_mirai;
+	uint8_t ecdh_secret[CHIAKI_ECDH_SECRET_SIZE];
 } ChiakiNagare;
 
 CHIAKI_EXPORT ChiakiErrorCode chiaki_nagare_run(struct chiaki_session_t *session);
diff --git a/lib/src/gkcrypt.c b/lib/src/gkcrypt.c
index eb84a05..25ce53e 100644
--- a/lib/src/gkcrypt.c
+++ b/lib/src/gkcrypt.c
@@ -24,6 +24,8 @@
 #include <openssl/evp.h>
 #include <openssl/hmac.h>
 
+#include "utils.h"
+
 
 static ChiakiErrorCode gkcrypt_gen_key_iv(ChiakiGKCrypt *gkcrypt, uint8_t index, uint8_t *handshake_key, uint8_t *ecdh_secret);
 
@@ -74,3 +76,73 @@ static ChiakiErrorCode gkcrypt_gen_key_iv(ChiakiGKCrypt *gkcrypt, uint8_t index,
 
 	return CHIAKI_ERR_SUCCESS;
 }
+
+static inline void counter_add(uint8_t *out, const uint8_t *base, int v)
+{
+	size_t i=CHIAKI_GKCRYPT_BLOCK_SIZE;
+	do
+	{
+		i--;
+		int r = (int)base[i] + v;
+		out[i] = (uint8_t)(r & 0xff);
+		v = r >> 8;
+	} while(i>0 && v);
+}
+
+static ChiakiErrorCode gkcrypt_gen_key_stream(ChiakiGKCrypt *gkcrypt, size_t key_pos, uint8_t *buf, size_t buf_size)
+{
+	assert(key_pos % CHIAKI_GKCRYPT_BLOCK_SIZE == 0);
+	assert(buf_size % CHIAKI_GKCRYPT_BLOCK_SIZE == 0);
+
+	EVP_CIPHER_CTX *ctx = EVP_CIPHER_CTX_new();
+	if(!ctx)
+		return CHIAKI_ERR_UNKNOWN;
+
+	if(!EVP_EncryptInit_ex(ctx, EVP_aes_128_ecb(), NULL, gkcrypt->key, NULL))
+	{
+		EVP_CIPHER_CTX_free(ctx);
+		return CHIAKI_ERR_UNKNOWN;
+	}
+
+	if(!EVP_CIPHER_CTX_set_padding(ctx, 0))
+	{
+		EVP_CIPHER_CTX_free(ctx);
+		return CHIAKI_ERR_UNKNOWN;
+	}
+
+	for(uint8_t *cur = buf, *end = buf + buf_size; cur < end; cur += CHIAKI_GKCRYPT_BLOCK_SIZE)
+		counter_add(cur, gkcrypt->iv, (int)key_pos++);
+
+	int outl;
+	EVP_EncryptUpdate(ctx, buf, &outl, buf, (int)buf_size);
+	if(outl != buf_size)
+	{
+		EVP_CIPHER_CTX_free(ctx);
+		return CHIAKI_ERR_UNKNOWN;
+	}
+
+	EVP_CIPHER_CTX_free(ctx);
+	return CHIAKI_ERR_SUCCESS;
+}
+
+CHIAKI_EXPORT ChiakiErrorCode chiaki_gkcrypt_decrypt(ChiakiGKCrypt *gkcrypt, size_t key_pos, uint8_t *buf, size_t buf_size)
+{
+	size_t padding_pre = key_pos % CHIAKI_GKCRYPT_BLOCK_SIZE;
+	size_t full_size = ((padding_pre + buf_size + CHIAKI_GKCRYPT_BLOCK_SIZE - 1) / CHIAKI_GKCRYPT_BLOCK_SIZE) * CHIAKI_GKCRYPT_BLOCK_SIZE;
+
+	uint8_t *key_stream = malloc(full_size);
+	if(!key_stream)
+		return CHIAKI_ERR_MEMORY;
+
+	ChiakiErrorCode err = gkcrypt_gen_key_stream(gkcrypt, key_pos - padding_pre, key_stream, full_size);
+	if(err != CHIAKI_ERR_SUCCESS)
+	{
+		free(key_stream);
+		return err;
+	}
+
+	xor_bytes(buf, key_stream + padding_pre, buf_size);
+	free(key_stream);
+
+	return CHIAKI_ERR_SUCCESS;
+}
\ No newline at end of file
diff --git a/lib/src/nagare.c b/lib/src/nagare.c
index c940275..6d89ea3 100644
--- a/lib/src/nagare.c
+++ b/lib/src/nagare.c
@@ -41,7 +41,8 @@
 static void nagare_takion_data(uint8_t *buf, size_t buf_size, void *user);
 static ChiakiErrorCode nagare_send_big(ChiakiNagare *nagare);
 static ChiakiErrorCode nagare_send_disconnect(ChiakiNagare *nagare);
-static void nagare_handle_bang(ChiakiNagare *nagare, tkproto_BangPayload *payload);
+static void nagare_takion_data_expect_bang(ChiakiNagare *nagare, uint8_t *buf, size_t buf_size);
+
 
 CHIAKI_EXPORT ChiakiErrorCode chiaki_nagare_run(ChiakiSession *session)
 {
@@ -104,6 +105,9 @@ CHIAKI_EXPORT ChiakiErrorCode chiaki_nagare_run(ChiakiSession *session)
 
 	CHIAKI_LOGI(&session->log, "Nagare successfully received bang\n");
 
+
+
+
 	CHIAKI_LOGI(&session->log, "Nagare is disconnecting\n");
 
 	nagare_send_disconnect(nagare);
@@ -121,8 +125,6 @@ error_bang_mirai:
 
 
 
-static void nagare_takion_data_expect_bang(ChiakiNagare *nagare, uint8_t *buf, size_t buf_size);
-
 static void nagare_takion_data(uint8_t *buf, size_t buf_size, void *user)
 {
 	ChiakiNagare *nagare = user;
@@ -198,11 +200,8 @@ static void nagare_takion_data_expect_bang(ChiakiNagare *nagare, uint8_t *buf, s
 		goto error;
 	}
 
-	CHIAKI_LOGI(nagare->log, "Nagare bang looks good so far\n");
-
-	uint8_t secret[CHIAKI_ECDH_SECRET_SIZE];
 	ChiakiErrorCode err = chiaki_ecdh_derive_secret(&nagare->session->ecdh,
-			secret,
+			nagare->ecdh_secret,
 			ecdh_pub_key_buf.buf, ecdh_pub_key_buf.size,
 			nagare->session->handshake_key,
 			ecdh_sig_buf.buf, ecdh_sig_buf.size);
@@ -213,8 +212,10 @@ static void nagare_takion_data_expect_bang(ChiakiNagare *nagare, uint8_t *buf, s
 		goto error;
 	}
 
-error:
 	chiaki_mirai_signal(&nagare->bang_mirai, true);
+	return;
+error:
+	chiaki_mirai_signal(&nagare->bang_mirai, false);
 }