diff --git a/src/encrypt.c b/src/encrypt.c
index 301dfca4..361592ac 100644
--- a/src/encrypt.c
+++ b/src/encrypt.c
@@ -1478,7 +1478,7 @@ int enc_init(const char *pass, const char *method)
     return m;
 }
 
-int ss_check_hash(char **buf_ptr, ssize_t *buf_len, struct chunk *chunk, int buf_size)
+int ss_check_hash(char **buf_ptr, ssize_t *buf_len, struct chunk *chunk, struct enc_ctx *ctx, int buf_size)
 {
     int i, j, k;
     char *buf = *buf_ptr;
@@ -1511,12 +1511,12 @@ int ss_check_hash(char **buf_ptr, ssize_t *buf_len, struct chunk *chunk, int buf
         if (cidx == chunk->len + AUTH_BYTES) {
             // Compare hash
             uint8_t *hash = (uint8_t *)malloc(chunk->len);
-            uint8_t key[MAX_KEY_LENGTH + sizeof(uint32_t)];
+            uint8_t key[MAX_IV_LENGTH + sizeof(uint32_t)];
 
-            memcpy(key, enc_key, enc_key_len);
-            memcpy(key + enc_key_len, &chunk->counter, sizeof(uint32_t));
+            memcpy(key, ctx->evp.iv, enc_key_len);
+            memcpy(key + enc_iv_len, &chunk->counter, sizeof(uint32_t));
             crypto_generichash(hash, HASH_BYTES, (uint8_t *)chunk->buf + AUTH_BYTES, chunk->len,
-                    key, enc_key_len + sizeof(uint32_t));
+                    key, enc_iv_len + sizeof(uint32_t));
 
             if (memcmp(hash, chunk->buf + CLEN_BYTES, HASH_BYTES) != 0) return 0;
 
@@ -1538,7 +1538,7 @@ int ss_check_hash(char **buf_ptr, ssize_t *buf_len, struct chunk *chunk, int buf
     return 1;
 }
 
-char *ss_gen_hash(char *buf, ssize_t *buf_len, uint32_t *counter, int buf_size)
+char *ss_gen_hash(char *buf, ssize_t *buf_len, uint32_t *counter, struct enc_ctx *ctx, int buf_size)
 {
     ssize_t blen = *buf_len;
     int size = max(AUTH_BYTES + blen, buf_size);
@@ -1549,11 +1549,11 @@ char *ss_gen_hash(char *buf, ssize_t *buf_len, uint32_t *counter, int buf_size)
 
     uint16_t chunk_len = htons((uint16_t)blen);
     uint8_t hash[HASH_BYTES];
-    uint8_t key[MAX_KEY_LENGTH + sizeof(uint32_t)];
+    uint8_t key[MAX_IV_LENGTH + sizeof(uint32_t)];
 
-    memcpy(key, enc_key, enc_key_len);
-    memcpy(key + enc_key_len, counter, sizeof(uint32_t));
-    crypto_generichash(hash, HASH_BYTES, (uint8_t *)buf, blen, key, enc_key_len + sizeof(uint32_t));
+    memcpy(key, ctx->evp.iv, enc_iv_len);
+    memcpy(key + enc_iv_len, counter, sizeof(uint32_t));
+    crypto_generichash(hash, HASH_BYTES, (uint8_t *)buf, blen, key, enc_iv_len + sizeof(uint32_t));
 
     memmove(buf + AUTH_BYTES, buf, blen);
     memcpy(buf + CLEN_BYTES, hash, HASH_BYTES);
diff --git a/src/encrypt.h b/src/encrypt.h
index df148af5..13a724ab 100644
--- a/src/encrypt.h
+++ b/src/encrypt.h
@@ -181,7 +181,7 @@ unsigned char *enc_md5(const unsigned char *d, size_t n, unsigned char *md);
 int ss_onetimeauth(char *auth, char *msg, int msg_len, struct enc_ctx *ctx);
 int ss_onetimeauth_verify(char *auth, char *msg, int msg_len, struct enc_ctx *ctx);
 
-int ss_check_hash(char **buf_ptr, ssize_t *buf_len, struct chunk *chunk, int buf_size);
-char *ss_gen_hash(char *buf, ssize_t *buf_len, uint32_t *counter, int buf_size);
+int ss_check_hash(char **buf_ptr, ssize_t *buf_len, struct chunk *chunk, struct enc_ctx *ctx, int buf_size);
+char *ss_gen_hash(char *buf, ssize_t *buf_len, uint32_t *counter, struct enc_ctx *ctx, int buf_size);
 
 #endif // _ENCRYPT_H
diff --git a/src/local.c b/src/local.c
index 016356b9..f84c2cc4 100644
--- a/src/local.c
+++ b/src/local.c
@@ -245,7 +245,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
             }
 
             if (!remote->direct && remote->send_ctx->connected && auth) {
-                remote->buf = ss_gen_hash(remote->buf, &r, &remote->counter, BUF_SIZE);
+                remote->buf = ss_gen_hash(remote->buf, &r, &remote->counter, server->e_ctx, BUF_SIZE);
             }
 
             // insert shadowsocks header
@@ -485,7 +485,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
 
                     if (r > 0) {
                         if (auth) {
-                            buf = ss_gen_hash(buf, &r, &remote->counter, BUF_SIZE);
+                            buf = ss_gen_hash(buf, &r, &remote->counter, server->e_ctx, BUF_SIZE);
                         }
                         memcpy(remote->buf + addr_len, buf, r);
                     }
diff --git a/src/redir.c b/src/redir.c
index 8c4427ae..7ba3397f 100644
--- a/src/redir.c
+++ b/src/redir.c
@@ -185,7 +185,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
     }
 
     if (auth) {
-        remote->buf = ss_gen_hash(remote->buf, &r, &remote->counter, BUF_SIZE);
+        remote->buf = ss_gen_hash(remote->buf, &r, &remote->counter, server->e_ctx, BUF_SIZE);
     }
 
     remote->buf = ss_encrypt(BUF_SIZE, remote->buf, &r, server->e_ctx);
diff --git a/src/server.c b/src/server.c
index 11de6f99..0e8f10a6 100644
--- a/src/server.c
+++ b/src/server.c
@@ -495,7 +495,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
 
     // handshake and transmit data
     if (server->stage == 5) {
-        if (server->auth && !ss_check_hash(&remote->buf, &r, server->chunk, BUF_SIZE)) {
+        if (server->auth && !ss_check_hash(&remote->buf, &r, server->chunk, server->e_ctx, BUF_SIZE)) {
             LOGE("hash error");
             report_addr(server->fd);
             close_and_free_server(EV_A_ server);
@@ -548,7 +548,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
          *    |  2   |    4    |  Variable   |      ...
          *    +------+---------+-------------+------+
          *
-         *    The key of BLAKE2b is (KEY + CHUNK ID)
+         *    The key of BLAKE2b is (IV + CHUNK ID)
          */
 
         int offset = 0;
@@ -684,7 +684,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
             memmove(server->buf, server->buf + offset, server->buf_len);
         }
 
-        if (server->auth && !ss_check_hash(&server->buf, &server->buf_len, server->chunk, BUF_SIZE)) {
+        if (server->auth && !ss_check_hash(&server->buf, &server->buf_len, server->chunk, server->d_ctx, BUF_SIZE)) {
             LOGE("hash error");
             report_addr(server->fd);
             close_and_free_server(EV_A_ server);
diff --git a/src/tunnel.c b/src/tunnel.c
index ef575355..9e848852 100644
--- a/src/tunnel.c
+++ b/src/tunnel.c
@@ -197,7 +197,7 @@ static void server_recv_cb(EV_P_ ev_io *w, int revents)
     }
 
     if (auth) {
-        remote->buf = ss_gen_hash(remote->buf, &r, &remote->counter, BUF_SIZE);
+        remote->buf = ss_gen_hash(remote->buf, &r, &remote->counter, server->e_ctx, BUF_SIZE);
     }
 
     remote->buf = ss_encrypt(BUF_SIZE, remote->buf, &r, server->e_ctx);