項目中需要用到3DES加密，進行與后臺的接口數據交互。因為加密傳參的過程是，先將字典類型的參數轉換為JSONstring，所以將3DES加密擴展到string類型里面，調用的時候方便

extension String{
    //3des加解密
    func threeDESEncryptOrDecrypt(op: Int) -> String? {
        //op傳1位加密，0為解密
        //CCOperation（kCCEncrypt）加密 1
        //CCOperation（kCCDecrypt) 解密 0

        var ccop = CCOperation()
        let key = "跟后臺同志商量好的加密串"
        let iv = "偏移量"
        // Key
        let keyData: NSData = (key as NSString).data(using: String.Encoding.utf8.rawValue) as NSData!
        let keyBytes         = UnsafeRawPointer(keyData.bytes)
        
        // 加密或解密的內容
        var data: NSData = NSData()
        if op == 1 {
            ccop = CCOperation(kCCEncrypt)
            data  = (self as NSString).data(using: String.Encoding.utf8.rawValue) as NSData!
        }
        else {
            ccop = CCOperation(kCCDecrypt)
            data = NSData(base64Encoded: self, options: NSData.Base64DecodingOptions.ignoreUnknownCharacters)!
        }
        
        let dataLength    = size_t(data.length)
        let dataBytes     = UnsafeRawPointer(data.bytes)
        
        // 返回數據
        let cryptData    = NSMutableData(length: Int(dataLength) + kCCBlockSize3DES)
        let cryptPointer = UnsafeMutableRawPointer(cryptData!.mutableBytes)
        let cryptLength  = size_t(cryptData!.length)
        
        //  可選 的初始化向量
        let viData :NSData = (iv as NSString).data(using: String.Encoding.utf8.rawValue) as NSData!
        let viDataBytes    = UnsafeRawPointer(viData.bytes)
        
        // 特定的幾個參數
        let keyLength              = size_t(kCCKeySize3DES)
        let operation: CCOperation = UInt32(ccop)
        let algoritm:  CCAlgorithm = UInt32(kCCAlgorithm3DES)
        let options:   CCOptions   = UInt32(kCCOptionPKCS7Padding)
        
        var numBytesCrypted :size_t = 0
        
        let cryptStatus = CCCrypt(operation, // 加密還是解密
            algoritm, // 算法類型
            options,  // 密碼塊的設置選項
            keyBytes, // 秘鑰的字節
            keyLength, // 秘鑰的長度
            viDataBytes, // 可選初始化向量的字節
            dataBytes, // 加解密內容的字節
            dataLength, // 加解密內容的長度
            cryptPointer, // output data buffer
            cryptLength,  // output data length available
            &numBytesCrypted) // real output data length
       
        if UInt32(cryptStatus) == UInt32(kCCSuccess) {
            cryptData!.length = Int(numBytesCrypted)
            if op == 1  {
                let base64cryptString = cryptData!.base64EncodedString(options: .lineLength64Characters)
                //返回加密的數據
                return base64cryptString
            }
            else {
                let base64cryptString = NSString(data: cryptData! as Data,  encoding: String.Encoding.utf8.rawValue) as String?
                //返回解密的數據
                return base64cryptString
            }
        } else {
            print("Error: \(cryptStatus)")
        }
        return nil
    }
}

//字典轉換為jsonString
func getJsonStringFromDictionary(dictionary:NSDictionary) -> String {
    if (!JSONSerialization.isValidJSONObject(dictionary)) {
        print("無法解析出JSONString")
        return ""
    }
    let data : NSData! = try? JSONSerialization.data(withJSONObject: dictionary, options: []) as NSData!
    let JSONString = String(data: data as Data, encoding: String.Encoding(rawValue: String.Encoding.utf8.rawValue))
    return JSONString!
}

在開始調用之前有一點需要跟大家交代一下，轉為3DES加密串之后傳給后臺或者接口后臺返回參數的時候是base64位的，base64進行http請求的時候不能識別"/"、"+"、"="等特殊字符，需要轉換一下

extension String{
//向后臺傳值的時候
func urlBase64EncodedString() -> String {
      let first = self.replacingOccurrences(of: "/", with: "_")
      let second = first.replacingOccurrences(of: "+", with: "-")
      let third = second.replacingOccurrences(of: "=", with: "")
      return third
}
//接收后臺返回的值的時候
func urlBase64DecodedString() -> String {
      let first = NSMutableString(string: self)
      let mod4:Int = first.length % 4
      print(first.length)
      if(mod4>0){
          var str = "===="
          let start1 = str.index(str.startIndex, offsetBy: 0)
          str = str.substring(from: start1)
          let end1 = str.index(str.startIndex, offsetBy: 4-mod4)
          let sub5 = str.substring(to: end1)
          first.append(sub5)
      }
      let second = first.replacingOccurrences(of: "_", with: "/")
      let third = second.replacingOccurrences(of: "-", with: "+")
      return third
  }
}

最后調用后臺接口傳參的時候只需要將參數字典轉化為jsonString,然后調用加密方法，賦值給后臺規定的加密參數就可以了

var params:[String:Any] = [:]
let paramsString = getJsonStringFromDictionary(dictionary: paramsDic as NSDictionary)
params["parameter"] = paramsString.threeDESEncryptOrDecrypt(op: 1)!.urlBase64EncodedString() 

解密后臺接口返回的數據并轉為字典類型

extension String{
//解密加轉換字典
  func toDecryptJsonDic() -> [String:Any]{
    let decryptJsonString = self.urlBase64DecodedString().threeDESEncryptOrDecrypt(op: 0)
    let decryptJsonDic = decryptJsonString?.toDictionary()
    if decryptJsonDic != nil {
        return decryptJsonDic!
    }
    return [String:Any].init()
  }
}
使用方式
返回值(jsonString). toDecryptJsonDic()