diff --git a/Cargo.toml b/Cargo.toml
index 89870d1..2f96782 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "colink"
-version = "0.1.17"
+version = "0.1.18"
 edition = "2021"
 description = "CoLink Rust SDK"
 license = "MIT"
@@ -16,7 +16,7 @@ chrono = "0.4"
 ctrlc = { version = "3.2", features = ["termination"] }
 futures-lite = "1.12"
 lapin = "2.1"
-openssl = { version = "0.10", features = ["vendored"] }
+sha2 = "0.10"
 prost = "0.10"
 rand = { version = "0.8.4", features = ["std_rng"] }
 secp256k1 = { version = "0.21.2", features = ["rand-std"] }
diff --git a/src/application.rs b/src/application.rs
index 79cf787..2b76d23 100644
--- a/src/application.rs
+++ b/src/application.rs
@@ -6,9 +6,9 @@ use lapin::{
     types::FieldTable,
     Connection, ConnectionProperties, Consumer,
 };
-use openssl::sha::sha256;
 use secp256k1::Secp256k1;
 use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
 use tonic::{
     metadata::MetadataValue,
     transport::{Certificate, Channel, ClientTlsConfig, Identity},
@@ -516,8 +516,11 @@ pub fn prepare_import_user_signature(
     msg.extend_from_slice(&signature_timestamp.to_le_bytes());
     msg.extend_from_slice(&expiration_timestamp.to_le_bytes());
     msg.extend_from_slice(&core_pub_key.serialize());
+    let mut hasher = Sha256::new();
+    hasher.update(&msg);
+    let sha256 = hasher.finalize();
     let signature = secp.sign_ecdsa(
-        &secp256k1::Message::from_slice(&sha256(&msg)).unwrap(),
+        &secp256k1::Message::from_slice(&sha256).unwrap(),
         user_sec_key,
     );
     (signature_timestamp, signature.serialize_compact().to_vec())