diff --git a/Package.swift b/Package.swift
index be13759..ef7d1be 100644
--- a/Package.swift
+++ b/Package.swift
@@ -8,9 +8,8 @@ let package = Package(
   platforms: [
     .macOS(.v10_15),
     .iOS(.v13),
-    .visionOS(.v1),
+    .watchOS(.v6),
     .tvOS(.v13),
-    .watchOS(.v6)
   ],
   products: [
     // Products define the executables and libraries a package produces, making them visible to other packages.
@@ -28,7 +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: [
@@ -45,5 +44,6 @@ let package = Package(
       name: "MinisignTests",
       dependencies: ["Minisign"]
     ),
-  ]
+  ],
+  swiftLanguageModes: [.v6]
 )
diff --git a/Package@swift-5.9.swift b/Package@swift-5.9.swift
new file mode 100644
index 0000000..33d3fa9
--- /dev/null
+++ b/Package@swift-5.9.swift
@@ -0,0 +1,43 @@
+// swift-tools-version: 5.9
+
+import PackageDescription
+
+let package = Package(
+  name: "Minisign",
+  platforms: [
+    .macOS(.v10_15),
+    .iOS(.v13),
+    .watchOS(.v6),
+    .tvOS(.v13),
+  ],
+  products: [
+    // Products define the executables and libraries a package produces, making them visible to other packages.
+    .library(
+      name: "Minisign",
+      targets: ["Minisign"]
+    )
+  ],
+  dependencies: [
+    .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: [
+    // Targets are the basic building blocks of a package, defining a module or a test suite.
+    // Targets can depend on other targets in this package and products from dependencies.
+    .target(
+      name: "Minisign",
+      dependencies: [
+        .product(name: "Crypto", package: "swift-crypto"),
+        .product(name: "BLAKE2", package: "swift-blake2"),
+      ],
+      swiftSettings: [
+        .define("UseSwiftCrypto")
+      ]
+    ),
+    .testTarget(
+      name: "MinisignTests",
+      dependencies: ["Minisign"]
+    ),
+  ],
+  swiftLanguageVersions: [.version("6"), .v5]
+)
diff --git a/README.md b/README.md
index 5a22615..30180f4 100644
--- a/README.md
+++ b/README.md
@@ -1,10 +1,14 @@
 # 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:
 
 - Convenient & efficient API for verifying (big) files
+- `Sendable` conformance & full Swift 6 support
 - Replaced C wrapping `swift-crypto-blake2` with [pure Swift implementation of blake2b](https://github.com/lovetodream/swift-blake2).
 - For Apple platforms, Swift Crypto dependency is now optional, controllable via trait `UseSwiftCrypto`.
 
diff --git a/Sources/Minisign/Minisign.swift b/Sources/Minisign/Minisign.swift
index 31bca54..ecaa5b4 100644
--- a/Sources/Minisign/Minisign.swift
+++ b/Sources/Minisign/Minisign.swift
@@ -6,12 +6,12 @@ import BLAKE2
 import Foundation
 
 #if UseSwiftCrypto
-  import Crypto
+  @preconcurrency import Crypto
 #else
-  import CryptoKit
+  @preconcurrency import CryptoKit
 #endif
 
-public enum SignatureAlgorithm: RawRepresentable {
+public enum SignatureAlgorithm: Sendable, RawRepresentable {
   case pureEdDSA
   case hashedEdDSA
 
@@ -39,7 +39,7 @@ public enum SignatureAlgorithm: RawRepresentable {
 private let untrustedCommentHeader = "untrusted comment: ".data(using: .utf8)!
 private let trustedCommentHeader = "trusted comment: ".data(using: .utf8)!
 
-public struct PublicKey {
+public struct PublicKey: Sendable {
   public let untrustedComment: String
   public let signatureAlgorithm: SignatureAlgorithm
   public let keyID: Data
@@ -87,13 +87,12 @@ public struct PublicKey {
   ///
   /// 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 }
@@ -115,7 +114,7 @@ public struct PublicKey {
   }
 }
 
-public struct Signature {
+public struct Signature: Sendable {
   public let untrustedComment: String
   public let signatureAlgorithm: SignatureAlgorithm
   public let keyID: Data