Fail on macOS 10.11 or lower

Package.swift

@@ -21,6 +21,7 @@ let package = Package(
     dependencies: [
         .Package(url: "https://github.com/IBM-Swift/BlueCryptor.git", majorVersion: 0, minor: 8),
         .Package(url: "https://github.com/IBM-Swift/BlueRSA.git", majorVersion: 0, minor: 1),
+        .Package(url: "https://github.com/IBM-Swift/HeliumLogger.git", majorVersion: 1, minor: 6),
     ],
     exclude: []
 )

Sources/KituraJWT/Algorithm.swift

@@ -56,12 +56,10 @@ public enum Algorithm {
         }
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func sign(_ input: String) -> Data? {
         return encryptionAlgortihm.sign(input)
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func verify(signature: Data, for input: String) -> Bool {
         return encryptionAlgortihm.verify(signature: signature, for: input)
     }

Sources/KituraJWT/BlueRSA.swift

@@ -15,6 +15,7 @@
  **/
 
 import CryptorRSA
+import LoggerAPI
 
 import Foundation
 
@@ -30,8 +31,11 @@ class BlueRSA: EncryptionAlgorithm {
         self.algorithm = algorithm
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func sign(_ data: Data) -> Data? {
+        guard #available(macOS 10.12, iOS 10.0, *) else {
+            Log.error("macOS 10.12.0 (Sierra) or higher or iOS 10.0 or higher is required by CryptorRSA")
+            return nil
+        }
         do {
             let privateKey = try CryptorRSA.createPrivateKey(with: key)
             let myPlaintext = CryptorRSA.createPlaintext(with: data)
@@ -45,16 +49,18 @@ class BlueRSA: EncryptionAlgorithm {
         }
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func sign(_ string: String, encoding: String.Encoding) -> Data? {
         guard let data: Data = string.data(using: encoding) else {
+            Log.error("macOS 10.12.0 (Sierra) or higher or iOS 10.0 or higher is required by CryptorRSA")
             return nil
         }
         return sign(data)
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func verify(signature: Data, for data: Data) -> Bool {
+        guard #available(macOS 10.12, iOS 10.0, *) else {
+            return false
+        }
         do {
             var publicKey: CryptorRSA.PublicKey
             switch keyType {
@@ -73,7 +79,6 @@ class BlueRSA: EncryptionAlgorithm {
         }
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func verify(signature: Data, for string: String, encoding: String.Encoding) -> Bool {
         guard let data: Data = string.data(using: encoding) else {
             return false

Sources/KituraJWT/EncryptionAlhorithm.swift

@@ -17,26 +17,20 @@
 import Foundation
 
 protocol EncryptionAlgorithm {
-    @available(macOS 10.12, iOS 10.0, *)
     func sign(_ data: Data) -> Data?
 
-    @available(macOS 10.12, iOS 10.0, *)
     func sign(_ string: String, encoding: String.Encoding) -> Data?
 
-    @available(macOS 10.12, iOS 10.0, *)
     func verify(signature: Data, for data: Data) -> Bool
 
-    @available(macOS 10.12, iOS 10.0, *)
     func verify(signature: Data, for string: String, encoding: String.Encoding) -> Bool
 }
 
 extension EncryptionAlgorithm {
-    @available(macOS 10.12, iOS 10.0, *)
     func sign(_ string: String, encoding: String.Encoding = .utf8) -> Data? {
         return sign(string, encoding: encoding)
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func verify(signature: Data, for string: String, encoding: String.Encoding = .utf8) -> Bool {
         return verify(signature: signature, for: string, encoding: encoding)
     }   

Sources/KituraJWT/JWT.swift

@@ -50,7 +50,6 @@ public struct JWT {
     /// - Parameter using algorithm: The algorithm to sign with.
     /// - Returns: A String with the encoded and signed JWT.
     /// - Throws: An error thrown during the encoding or signing.
-    @available(macOS 10.12, iOS 10.0, *)
     public mutating func sign(using algorithm: Algorithm) throws -> String? {
         header[.alg] = algorithm.name
         guard let encodedHeader = try header.encode(),
@@ -71,7 +70,6 @@ public struct JWT {
     /// - Parameter using algorithm: The algorithm to verify with.
     /// - Returns: A Bool indicating whether the verification was successful.
     /// - Throws: An error thrown during the verification.
-    @available(macOS 10.12, iOS 10.0, *)
     public static func verify(_ jwt: String, using algorithm: Algorithm) throws -> Bool {
         let components = jwt.components(separatedBy: ".")
         guard components.count == 3,

Tests/KituraJWTTests/TestJWT.swift

@@ -28,16 +28,15 @@ import Foundation
 let rsaPrivateKey = read(fileName: "rsa_private_key")
 let rsaPublicKey = read(fileName: "rsa_public_key")
 
+@available(macOS 10.12, iOS 10.0, *)
 class TestJWT: XCTestCase {
 
-    @available(macOS 10.12, iOS 10.0, *)
     static var allTests: [(String, (TestJWT) -> () throws -> Void)] {
         return [
             ("testSign", testSign),
         ]
     }
 
-    @available(macOS 10.12, iOS 10.0, *)
     func testSign() {
 
         var jwt = JWT(header: Header([.alg:"rs256"]), claims: Claims([.name:"Kitura"]))