diff --git a/lib/include/chiaki/common.h b/lib/include/chiaki/common.h
index 8827dcc..071f42c 100644
--- a/lib/include/chiaki/common.h
+++ b/lib/include/chiaki/common.h
@@ -28,17 +28,17 @@ extern "C" {
 typedef enum
 {
 	CHIAKI_ERR_SUCCESS = 0,
-	CHIAKI_ERR_PARSE_ADDR = 1,
-	CHIAKI_ERR_THREAD = 2,
-	CHIAKI_ERR_MEMORY = 3,
-	CHIAKI_ERR_NETWORK = 4,
-	CHIAKI_ERR_INVALID_DATA = 5,
-	CHIAKI_ERR_BUF_TOO_SMALL = 6
+	CHIAKI_ERR_UNKNOWN,
+	CHIAKI_ERR_PARSE_ADDR,
+	CHIAKI_ERR_THREAD,
+	CHIAKI_ERR_MEMORY,
+	CHIAKI_ERR_NETWORK,
+	CHIAKI_ERR_INVALID_DATA,
+	CHIAKI_ERR_BUF_TOO_SMALL
 } ChiakiErrorCode;
 
 CHIAKI_EXPORT const char *chiaki_error_string(ChiakiErrorCode code);
 
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/include/chiaki/rpcrypt.h b/lib/include/chiaki/rpcrypt.h
index 0d0e72a..d0d3f1f 100644
--- a/lib/include/chiaki/rpcrypt.h
+++ b/lib/include/chiaki/rpcrypt.h
@@ -30,11 +30,16 @@ extern "C" {
 
 typedef struct chiaki_rpcrypt_t
 {
-
+	uint8_t bright[CHIAKI_KEY_BYTES];
+	uint8_t ambassador[CHIAKI_KEY_BYTES];
+	struct hmac_ctx_st *hmac_ctx;
 } ChiakiRPCrypt;
 
 CHIAKI_EXPORT void chiaki_rpcrypt_bright_ambassador(uint8_t *bright, uint8_t *ambassador, const uint8_t *nonce, const uint8_t *morning);
 
+CHIAKI_EXPORT void chiaki_rpcrypt_init(ChiakiRPCrypt *rpcrypt, const uint8_t *nonce, const uint8_t *morning);
+CHIAKI_EXPORT ChiakiErrorCode chiaki_rpcrypt_generate_iv(ChiakiRPCrypt *rpcrypt, uint8_t *iv, uint64_t counter);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/src/common.c b/lib/src/common.c
index 42b5a60..45f34cc 100644
--- a/lib/src/common.c
+++ b/lib/src/common.c
@@ -17,6 +17,7 @@
 
 #include <chiaki/common.h>
 
+
 CHIAKI_EXPORT const char *chiaki_error_string(ChiakiErrorCode code)
 {
 	switch(code)
@@ -36,4 +37,4 @@ CHIAKI_EXPORT const char *chiaki_error_string(ChiakiErrorCode code)
 		default:
 			return "Unknown";
 	}
-}
\ No newline at end of file
+}
diff --git a/lib/src/rpcrypt.c b/lib/src/rpcrypt.c
index e838251..6b6c2b3 100644
--- a/lib/src/rpcrypt.c
+++ b/lib/src/rpcrypt.c
@@ -17,6 +17,10 @@
 
 #include <chiaki/rpcrypt.h>
 
+#include <openssl/hmac.h>
+#include <openssl/evp.h>
+
+#include <string.h>
 
 
 CHIAKI_EXPORT void chiaki_rpcrypt_bright_ambassador(uint8_t *bright, uint8_t *ambassador, const uint8_t *nonce, const uint8_t *morning)
@@ -42,4 +46,37 @@ CHIAKI_EXPORT void chiaki_rpcrypt_bright_ambassador(uint8_t *bright, uint8_t *am
 		v ^= nonce[i];
 		bright[i] = v;
 	}
+}
+
+
+CHIAKI_EXPORT void chiaki_rpcrypt_init(ChiakiRPCrypt *rpcrypt, const uint8_t *nonce, const uint8_t *morning)
+{
+	chiaki_rpcrypt_bright_ambassador(rpcrypt->bright, rpcrypt->ambassador, nonce, morning);
+}
+
+CHIAKI_EXPORT ChiakiErrorCode chiaki_rpcrypt_generate_iv(ChiakiRPCrypt *rpcrypt, uint8_t *iv, uint64_t counter)
+{
+	uint8_t hmac_key[] = { 0xac, 0x07, 0x88, 0x83, 0xc8, 0x3a, 0x1f, 0xe8, 0x11, 0x46, 0x3a, 0xf3, 0x9e, 0xe3, 0xe3, 0x77 };
+
+	uint8_t buf[CHIAKI_KEY_BYTES + 8];
+	memcpy(buf, rpcrypt->ambassador, CHIAKI_KEY_BYTES);
+	buf[CHIAKI_KEY_BYTES + 0] = (uint8_t)((counter >> 0x38) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 1] = (uint8_t)((counter >> 0x30) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 2] = (uint8_t)((counter >> 0x28) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 3] = (uint8_t)((counter >> 0x20) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 4] = (uint8_t)((counter >> 0x18) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 5] = (uint8_t)((counter >> 0x10) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 6] = (uint8_t)((counter >> 0x08) & 0xff);
+	buf[CHIAKI_KEY_BYTES + 7] = (uint8_t)((counter >> 0x00) & 0xff);
+
+	uint8_t hmac[32];
+	unsigned int hmac_len = 0;
+	if(!HMAC(EVP_sha256(), hmac_key, CHIAKI_KEY_BYTES, buf, sizeof(buf), hmac, &hmac_len))
+		return CHIAKI_ERR_UNKNOWN;
+
+	if(hmac_len < CHIAKI_KEY_BYTES)
+		return CHIAKI_ERR_UNKNOWN;
+
+	memcpy(iv, hmac, CHIAKI_KEY_BYTES);
+	return CHIAKI_ERR_SUCCESS;
 }
\ No newline at end of file
diff --git a/test/rpcrypt.c b/test/rpcrypt.c
index d02ee93..6fdf2de 100644
--- a/test/rpcrypt.c
+++ b/test/rpcrypt.c
@@ -19,10 +19,13 @@
 
 #include <chiaki/rpcrypt.h>
 
+
+static const uint8_t nonce[] = { 0x43, 0x9, 0x67, 0xae, 0x36, 0x4b, 0x1c, 0x45, 0x26, 0x62, 0x37, 0x7a, 0xbf, 0x3f, 0xe9, 0x39 };
+static const uint8_t morning[] = { 0xd2, 0x78, 0x9f, 0x51, 0x85, 0xa7, 0x99, 0xa2, 0x44, 0x52, 0x77, 0x9c, 0x2b, 0x83, 0xcf, 0x7 };
+
+
 static MunitResult test_bright_ambassador(const MunitParameter params[], void *user)
 {
-	static const uint8_t nonce[] = { 0x43, 0x9, 0x67, 0xae, 0x36, 0x4b, 0x1c, 0x45, 0x26, 0x62, 0x37, 0x7a, 0xbf, 0x3f, 0xe9, 0x39 };
-	static const uint8_t morning[] = { 0xd2, 0x78, 0x9f, 0x51, 0x85, 0xa7, 0x99, 0xa2, 0x44, 0x52, 0x77, 0x9c, 0x2b, 0x83, 0xcf, 0x7 };
 	static const uint8_t bright_expected[] = { 0xa4, 0x4e, 0x2a, 0x16, 0x5e, 0x20, 0xd3, 0xf, 0xaa, 0x11, 0x8b, 0xc7, 0x7c, 0xa7, 0xdc, 0x11 };
 	static const uint8_t ambassador_expected[] = { 0x1d, 0xa8, 0xb9, 0x1f, 0x6e, 0x26, 0x64, 0x2e, 0xbc, 0x8, 0x8b, 0x0, 0x4f, 0x1, 0x5b, 0x52 };
 
@@ -36,6 +39,43 @@ static MunitResult test_bright_ambassador(const MunitParameter params[], void *u
 	return MUNIT_OK;
 }
 
+static MunitResult test_iv(const MunitParameter params[], void *user)
+{
+	static const uint8_t iv_a_expected[] = { 0x6, 0x29, 0xbe, 0x4, 0xe9, 0x91, 0x1c, 0x48, 0xb4, 0x5c, 0x2, 0x6d, 0xb7, 0xb7, 0x88, 0x46 };
+	static const uint8_t iv_b_expected[] = { 0x3f, 0xd0, 0x83, 0xa, 0xc7, 0x30, 0xfc, 0x56, 0x75, 0x2d, 0xbe, 0xb8, 0x2c, 0x68, 0xa7, 0x4 };
+
+	ChiakiRPCrypt rpcrypt;
+	ChiakiErrorCode err;
+
+	chiaki_rpcrypt_init(&rpcrypt, nonce, morning);
+
+	uint8_t iv[CHIAKI_KEY_BYTES];
+
+	err = chiaki_rpcrypt_generate_iv(&rpcrypt, iv, 0);
+	if(err != CHIAKI_ERR_SUCCESS)
+		return MUNIT_ERROR;
+	munit_assert_memory_equal(CHIAKI_KEY_BYTES, iv, iv_a_expected);
+
+	err = chiaki_rpcrypt_generate_iv(&rpcrypt, iv, 0);
+	if(err != CHIAKI_ERR_SUCCESS)
+		return MUNIT_ERROR;
+	munit_assert_memory_equal(CHIAKI_KEY_BYTES, iv, iv_a_expected);
+
+	err = chiaki_rpcrypt_generate_iv(&rpcrypt, iv, 0x0102030405060708);
+	if(err != CHIAKI_ERR_SUCCESS)
+		return MUNIT_ERROR;
+	munit_assert_memory_equal(CHIAKI_KEY_BYTES, iv, iv_b_expected);
+
+	err = chiaki_rpcrypt_generate_iv(&rpcrypt, iv, 0x0102030405060708);
+	if(err != CHIAKI_ERR_SUCCESS)
+		return MUNIT_ERROR;
+	munit_assert_memory_equal(CHIAKI_KEY_BYTES, iv, iv_b_expected);
+
+	return MUNIT_OK;
+}
+
+
+
 MunitTest tests_rpcrypt[] = {
 	{
 		"/bright_ambassador",
@@ -45,5 +85,13 @@ MunitTest tests_rpcrypt[] = {
 		MUNIT_TEST_OPTION_NONE,
 		NULL
 	},
+	{
+		"/iv",
+		test_iv,
+		NULL,
+		NULL,
+		MUNIT_TEST_OPTION_NONE,
+		NULL
+	},
 	{ NULL, NULL, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL }
 };
\ No newline at end of file