事实证明，我完全把这个复杂化了。

我不需要导入任何外部库或SDK，我只需要一个桥接头文件即可 #import <CommonCrypto/CommonCrypto.h>

override func viewDidLoad() {
    super.viewDidLoad()
    myEncrypt("my string to encrypt") 
}

func myEncrypt(encryptData:String) -> NSData?{

        var myKeyData : NSData = ("myEncryptionKey" as NSString).dataUsingEncoding(NSUTF8StringEncoding)!
        var myRawData : NSData = encryptData.dataUsingEncoding(NSUTF8StringEncoding)!
        var iv : [UInt8] = [56, 101, 63, 23, 96, 182, 209, 205]  // I didn't use
        var buffer_size : size_t = myRawData.length + kCCBlockSize3DES
        var buffer = UnsafeMutablePointer<NSData>.alloc(buffer_size)
        var num_bytes_encrypted : size_t = 0

        let operation: CCOperation = UInt32(kCCEncrypt)
        let algoritm:  CCAlgorithm = UInt32(kCCAlgorithm3DES)
        let options:   CCOptions   = UInt32(kCCOptionECBMode + kCCOptionPKCS7Padding)
        let keyLength        = size_t(kCCKeySize3DES)

        var Crypto_status: CCCryptorStatus = CCCrypt(operation, algoritm, options, myKeyData.bytes, keyLength, nil, myRawData.bytes, myRawData.length, buffer, buffer_size, &num_bytes_encrypted)

        if UInt32(Crypto_status) == UInt32(kCCSuccess){

            var myResult: NSData = NSData(bytes: buffer, length: num_bytes_encrypted)

            free(buffer)
            println("my result \(myResult)") //This just prints the data

            let keyData: NSData = myResult
            let hexString = keyData.toHexString()
            println("hex result \(hexString)") // I needed a hex string output


            myDecrypt(myResult) // sent straight to the decryption function to test the data output is the same
            return myResult
        }else{
            free(buffer)
            return nil
        }   
    }


func myDecrypt(decryptData : NSData) -> NSData?{

    var mydata_len : Int = decryptData.length
    var keyData : NSData = ("myEncryptionKey" as NSString).dataUsingEncoding(NSUTF8StringEncoding)!

    var buffer_size : size_t = mydata_len+kCCBlockSizeAES128
    var buffer = UnsafeMutablePointer<NSData>.alloc(buffer_size)
    var num_bytes_encrypted : size_t = 0

    var iv : [UInt8] = [56, 101, 63, 23, 96, 182, 209, 205]  // I didn't use

    let operation: CCOperation = UInt32(kCCDecrypt)
    let algoritm:  CCAlgorithm = UInt32(kCCAlgorithm3DES)
    let options:   CCOptions   = UInt32(kCCOptionECBMode + kCCOptionPKCS7Padding)
    let keyLength        = size_t(kCCKeySize3DES)

    var decrypt_status : CCCryptorStatus = CCCrypt(operation, algoritm, options, keyData.bytes, keyLength, nil, decryptData.bytes, mydata_len, buffer, buffer_size, &num_bytes_encrypted)

    if UInt32(decrypt_status) == UInt32(kCCSuccess){

        var myResult : NSData = NSData(bytes: buffer, length: num_bytes_encrypted)
        free(buffer)
        println("decrypt \(myResult)")

        var stringResult = NSString(data: myResult, encoding:NSUTF8StringEncoding)
        println("my decrypt string \(stringResult!)")
        return myResult
    }else{
        free(buffer)
        return nil

    }
}

我希望这可以帮助别人。