diff --git a/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift b/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift
index 579264d..0d237aa 100644
--- a/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift
+++ b/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift
@@ -9,7 +9,7 @@ import NIOFoundationCompat
 
 public class AppStoreServerAPIClient {
 
-    public enum ConfigurationError: Error {
+    public enum ConfigurationError: Error, Hashable, Sendable {
         /// Xcode is not a supported environment for an AppStoreServerAPIClient
         case invalidEnvironment
     }
@@ -345,7 +345,9 @@ public enum APIResult<T> {
     case failure(statusCode: Int?, rawApiError: Int64?, apiError: APIError?, errorMessage: String?, causedBy: Error?)
 }
 
-public enum APIError: Int64 {
+extension APIResult: Sendable where T: Sendable {}
+
+public enum APIError: Int64, Hashable, Sendable {
     ///An error that indicates an invalid request.
     ///
     ///[GeneralBadRequestError](https://developer.apple.com/documentation/appstoreserverapi/generalbadrequesterror)
@@ -633,7 +635,7 @@ public enum APIError: Int64 {
     case generalInternalRetryable = 5000001
 }
 
-public enum GetTransactionHistoryVersion: String {
+public enum GetTransactionHistoryVersion: String, Hashable, Sendable {
     @available(*, deprecated)
     case v1 = "v1"
     case v2 = "v2"
diff --git a/Sources/AppStoreServerLibrary/ChainVerifier.swift b/Sources/AppStoreServerLibrary/ChainVerifier.swift
index 3d3ae67..8872699 100644
--- a/Sources/AppStoreServerLibrary/ChainVerifier.swift
+++ b/Sources/AppStoreServerLibrary/ChainVerifier.swift
@@ -8,8 +8,7 @@ import Crypto
 import AsyncHTTPClient
 import NIOFoundationCompat
 
-class ChainVerifier {
-    
+actor ChainVerifier {
     private static let EXPECTED_CHAIN_LENGTH = 3
     private static let EXPECTED_JWT_SEGMENTS = 3
     private static let EXPECTED_ALGORITHM = "ES256"
@@ -28,7 +27,7 @@ class ChainVerifier {
         self.verifiedPublicKeyCache = [:]
     }
     
-    func verify<T: DecodedSignedData>(signedData: String, type: T.Type, onlineVerification: Bool, environment: AppStoreEnvironment) async -> VerificationResult<T> where T: Decodable {
+    func verify<T: DecodedSignedData>(signedData: String, type: T.Type, onlineVerification: Bool, environment: AppStoreEnvironment) async -> VerificationResult<T> where T: Decodable & Sendable {
         let header: JWTHeader;
         let decodedBody: T;
         do {
@@ -120,7 +119,7 @@ class ChainVerifier {
         return verificationResult
     }
     
-    func verifyChainWithoutCaching(leaf: Certificate, intermediate: Certificate, online: Bool, validationTime: Date) async -> X509.VerificationResult {
+    nonisolated func verifyChainWithoutCaching(leaf: Certificate, intermediate: Certificate, online: Bool, validationTime: Date) async -> X509.VerificationResult {
         var verifier = Verifier(rootCertificates: self.store) {
             RFC5280Policy(validationTime: validationTime)
             AppStoreOIDPolicy()
@@ -132,7 +131,7 @@ class ChainVerifier {
         return await verifier.validate(leafCertificate: leaf, intermediates: intermediateStore)
     }
     
-    func getDate() -> Date {
+    nonisolated func getDate() -> Date {
         return Date()
     }
 }
@@ -226,6 +225,10 @@ public enum VerificationResult<T> {
     case invalid(VerificationError)
 }
 
+extension VerificationResult: Equatable where T: Equatable {}
+extension VerificationResult: Hashable where T: Hashable {}
+extension VerificationResult: Sendable where T: Sendable {}
+
 public enum VerificationError: Hashable, Sendable {
     case INVALID_JWT_FORMAT
     case INVALID_CERTIFICATE
diff --git a/Sources/AppStoreServerLibrary/SignedDataVerifier.swift b/Sources/AppStoreServerLibrary/SignedDataVerifier.swift
index 2df7b3a..df008c5 100644
--- a/Sources/AppStoreServerLibrary/SignedDataVerifier.swift
+++ b/Sources/AppStoreServerLibrary/SignedDataVerifier.swift
@@ -3,9 +3,9 @@
 import Foundation
 
 ///A verifier and decoder class designed to decode signed data from the App Store.
-public struct SignedDataVerifier {
+public struct SignedDataVerifier: Sendable {
 
-    public enum ConfigurationError: Error {
+    public enum ConfigurationError: Error, Hashable, Sendable {
         case INVALID_APP_APPLE_ID
     }
 
@@ -148,7 +148,7 @@ public struct SignedDataVerifier {
         return appTransactionResult
     }
     
-    private func decodeSignedData<T: DecodedSignedData>(signedData: String, type: T.Type) async -> VerificationResult<T> where T : Decodable {
+    private func decodeSignedData<T: DecodedSignedData>(signedData: String, type: T.Type) async -> VerificationResult<T> where T : Decodable & Sendable {
         return await chainVerifier.verify(signedData: signedData, type: type, onlineVerification: self.enableOnlineChecks, environment: self.environment)
     }
 }