diff --git a/kbs/src/http/attest.rs b/kbs/src/http/attest.rs
index c8dd2426e..5089fc00d 100644
--- a/kbs/src/http/attest.rs
+++ b/kbs/src/http/attest.rs
@@ -11,8 +11,27 @@ use base64::engine::general_purpose::{STANDARD, URL_SAFE_NO_PAD};
 use base64::Engine;
 use kbs_types::Challenge;
 use log::{debug, error, info};
+use semver::{BuildMetadata, Prerelease, Version, VersionReq};
 use serde_json::json;
 
+static KBS_MAJOR_VERSION: u64 = 0;
+static KBS_MINOR_VERSION: u64 = 1;
+static KBS_PATCH_VERSION: u64 = 0;
+
+lazy_static! {
+    static ref VERSION_REQ: VersionReq = {
+        let kbs_version = Version {
+            major: KBS_MAJOR_VERSION,
+            minor: KBS_MINOR_VERSION,
+            patch: KBS_PATCH_VERSION,
+            pre: Prerelease::EMPTY,
+            build: BuildMetadata::EMPTY,
+        };
+
+        VersionReq::parse(&format!("<={kbs_version}")).unwrap()
+    };
+}
+
 /// POST /auth
 pub(crate) async fn auth(
     request: web::Json<Request>,
@@ -22,6 +41,14 @@ pub(crate) async fn auth(
 ) -> Result<HttpResponse> {
     info!("Auth API called.");
     debug!("Auth Request: {:?}", &request);
+    let version = Version::parse(&request.version).unwrap();
+    if !VERSION_REQ.matches(&version) {
+        raise_error!(Error::ProtocolVersion(format!(
+            "expected version: {}, requested version: {}",
+            *VERSION_REQ,
+            request.version.clone()
+        )));
+    }
 
     let challenge = attestation_service
         .generate_challenge(request.tee, request.extra_params.clone())
diff --git a/kbs/src/http/error.rs b/kbs/src/http/error.rs
index 147cc3e33..d278e2d8f 100644
--- a/kbs/src/http/error.rs
+++ b/kbs/src/http/error.rs
@@ -58,6 +58,9 @@ pub enum Error {
     #[error("Resource not permitted.")]
     PolicyReject,
 
+    #[error("KBS Client Protocol Version Mismatch: {0}")]
+    ProtocolVersion(String),
+
     #[error("Public key get failed: {0}")]
     PublicKeyGetFailed(String),
 
@@ -140,6 +143,7 @@ mod tests {
     #[case(Error::JWEFailed("test".into()))]
     #[case(Error::PolicyEndpoint("test".into()))]
     #[case(Error::PolicyReject)]
+    #[case(Error::ProtocolVersion("test".into()))]
     #[case(Error::PublicKeyGetFailed("test".into()))]
     #[case(Error::ReadSecretFailed("test".into()))]
     #[case(Error::SetSecretFailed("test".into()))]
diff --git a/kbs/src/lib.rs b/kbs/src/lib.rs
index 1eb7523e8..5d5177598 100644
--- a/kbs/src/lib.rs
+++ b/kbs/src/lib.rs
@@ -24,7 +24,6 @@ use attestation::AttestationService;
 use jwt_simple::prelude::Ed25519PublicKey;
 #[cfg(feature = "resource")]
 use resource::RepositoryConfig;
-use semver::{BuildMetadata, Prerelease, Version, VersionReq};
 #[cfg(feature = "as")]
 use std::sync::Arc;
 use std::{net::SocketAddr, path::PathBuf};
@@ -68,28 +67,11 @@ mod token;
 /// Resource Policy Engine
 pub mod policy_engine;
 
-static KBS_PREFIX: &str = "/kbs";
-static KBS_MAJOR_VERSION: u64 = 0;
-static KBS_MINOR_VERSION: u64 = 1;
-static KBS_PATCH_VERSION: u64 = 0;
-
-lazy_static! {
-    static ref VERSION_REQ: VersionReq = {
-        let kbs_version = Version {
-            major: KBS_MAJOR_VERSION,
-            minor: KBS_MINOR_VERSION,
-            patch: KBS_PATCH_VERSION,
-            pre: Prerelease::EMPTY,
-            build: BuildMetadata::EMPTY,
-        };
-
-        VersionReq::parse(&format!("<={kbs_version}")).unwrap()
-    };
-}
+static KBS_PREFIX: &str = "/kbs/v0";
 
 macro_rules! kbs_path {
     ($path:expr) => {
-        format!("{}/v{}/{}", KBS_PREFIX, KBS_MAJOR_VERSION, $path)
+        format!("{}/{}", KBS_PREFIX, $path)
     };
 }
 
diff --git a/kbs/src/session.rs b/kbs/src/session.rs
index 6c075defd..ec2169d3b 100644
--- a/kbs/src/session.rs
+++ b/kbs/src/session.rs
@@ -6,10 +6,9 @@ use actix_web::cookie::{
     time::{Duration, OffsetDateTime},
     Cookie,
 };
-use anyhow::{bail, Result};
+use anyhow::Result;
 use kbs_types::{Challenge, Request};
 use log::warn;
-use semver::Version;
 use uuid::Uuid;
 
 pub(crate) static KBS_SESSION_ID: &str = "kbs-session-id";
@@ -52,10 +51,6 @@ macro_rules! impl_member {
 
 impl SessionStatus {
     pub fn auth(request: Request, timeout: i64, challenge: Challenge) -> Result<Self> {
-        let version = Version::parse(&request.version).map_err(anyhow::Error::from)?;
-        if !crate::VERSION_REQ.matches(&version) {
-            bail!("Invalid Request version {}", request.version);
-        }
         let id = Uuid::new_v4().as_simple().to_string();
 
         let timeout = OffsetDateTime::now_utc() + Duration::minutes(timeout);