diff --git a/Package.swift b/Package.swift
index 9c0c629..ef7d1be 100644
--- a/Package.swift
+++ b/Package.swift
@@ -27,7 +27,7 @@ let package = Package(
     .default(enabledTraits: ["UseSwiftCrypto"]),
   ],
   dependencies: [
-    .package(url: "https://github.com/apple/swift-crypto", from: "2.0.0"),
+    .package(url: "https://github.com/apple/swift-crypto", "1.0.0" ..< "4.0.0"),
     .package(url: "https://github.com/lovetodream/swift-blake2", from: "0.1.0")
   ],
   targets: [
@@ -44,5 +44,6 @@ let package = Package(
       name: "MinisignTests",
       dependencies: ["Minisign"]
     ),
-  ]
+  ],
+  swiftLanguageModes: [.v6]
 )
diff --git a/Package@swift-5.8.swift b/Package@swift-5.9.swift
similarity index 90%
rename from Package@swift-5.8.swift
rename to Package@swift-5.9.swift
index 46b4194..33d3fa9 100644
--- a/Package@swift-5.8.swift
+++ b/Package@swift-5.9.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 5.8
+// swift-tools-version: 5.9
 
 import PackageDescription
 
@@ -18,7 +18,7 @@ let package = Package(
     )
   ],
   dependencies: [
-    .package(url: "https://github.com/apple/swift-crypto", from: "2.0.0"),
+    .package(url: "https://github.com/apple/swift-crypto", "1.0.0" ..< "4.0.0"),
     .package(url: "https://github.com/lovetodream/swift-blake2", from: "0.1.0"),
   ],
   targets: [
diff --git a/README.md b/README.md
index 4504a90..30180f4 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,8 @@
 # Swift Minisign
 
+[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Flaosb%2Fswift-minisign%2Fbadge%3Ftype%3Dplatforms)](https://swiftpackageindex.com/laosb/swift-minisign)
+[![](https://img.shields.io/endpoint?url=https%3A%2F%2Fswiftpackageindex.com%2Fapi%2Fpackages%2Flaosb%2Fswift-minisign%2Fbadge%3Ftype%3Dswift-versions)](https://swiftpackageindex.com/laosb/swift-minisign)
+
 Swift implementation of Minisign, a simple and secure tool for signing and verifying files.
 
 This is a fork of [slarew/swift-minisign](https://github.com/slarew/swift-minisign), with these improvements:
diff --git a/Sources/Minisign/Minisign.swift b/Sources/Minisign/Minisign.swift
index 4093222..ecaa5b4 100644
--- a/Sources/Minisign/Minisign.swift
+++ b/Sources/Minisign/Minisign.swift
@@ -6,9 +6,9 @@ import BLAKE2
 import Foundation
 
 #if UseSwiftCrypto
-  import Crypto
+  @preconcurrency import Crypto
 #else
-  import CryptoKit
+  @preconcurrency import CryptoKit
 #endif
 
 public enum SignatureAlgorithm: Sendable, RawRepresentable {
@@ -87,13 +87,12 @@ public struct PublicKey: Sendable {
   ///
   /// This method reads the file in chunks to avoid loading the entire file into memory, but does so in a blocking manner.
   /// It's recommended to use this method in a background thread or task.
-  public func isValidSignature(_ signature: Signature, forFileAt url: URL) throws -> Bool {
+  public func isValidSignature(_ signature: Signature, forFileAt url: URL, bufferSize: Int = 8192) throws -> Bool {
     guard signature.signatureAlgorithm == .hashedEdDSA else { throw SignatureVerifyError.algorithmNotSupportedForFile }
     var blake2b = try! BLAKE2b()
 
     let fileHandle = try FileHandle(forReadingFrom: url)
 
-    let bufferSize = 4096
     while true {
       let data = fileHandle.readData(ofLength: bufferSize)
       if data.isEmpty { break }