如何导出使用SecKeyGeneratePair生成的公钥<SecKey>并在服务器上使用？

我使用SecKeyGeneratePair生成了一个守护者。

        var publicKeyPtr, privateKeyPtr: Unmanaged?

        let publicKeyParameters: [String: AnyObject] = [
            kSecAttrIsPermanent: true,
            kSecAttrApplicationTag: "com.example.site.public"
        ]
        let privateKeyParameters: [String: AnyObject] = [
            kSecAttrIsPermanent: true,
            kSecAttrApplicationTag: "com.example.site.private"
        ]
        let parameters: [String: AnyObject] = [
            kSecAttrKeyType: kSecAttrKeyTypeRSA,
            kSecAttrKeySizeInBits: 2048,
            kSecPublicKeyAttrs.takeUnretainedValue() as String: publicKeyParameters,
            kSecPrivateKeyAttrs.takeUnretainedValue() as String: privateKeyParameters
        ]
        let result = SecKeyGeneratePair(parameters, &publicKeyPtr, &privateKeyPtr)
        let publicKey = publicKeyPtr!.takeRetainedValue()
        let privateKey = privateKeyPtr!.takeRetainedValue()
        let blockSize = SecKeyGetBlockSize(publicKey)

如果我打印出publicKey，我可以看到模数，我很确定这是我所需要的：

publicKey: 

但是我无法弄清楚如何导出密钥，因此可以将其发送到服务器以供使用。

根据我的理解。一个SecKey存储在钥匙串中，并且是指向它的指针，块大小是密钥在内存中的长度。因此，从理论上讲，我可以将其提取为NSData，然后将其转换为服务器可以读取的内容。从理论上讲，我认为这是行得通的，但我在实践中碰壁了。所有帮助将不胜感激。

SecItemCopyMatching 是给你的：

var dataPtr:Unmanaged?
let query: [String:AnyObject] = [
    kSecClass: kSecClassKey,
    kSecAttrApplicationTag: "com.example.site.public",
    kSecReturnData: kCFBooleanTrue
]
let qResult = SecItemCopyMatching(query, &dataPtr)

// error handling with `qResult` ...

let publicKeyData = dataPtr!.takeRetainedValue() as NSData

// convert to Base64 string
let base64PublicKey = publicKeyData.base64EncodedStringWithOptions(nil)

斯威夫特4：

var dataPtr:CFTypeRef?
let query: [String: Any] = [
    kSecClass as String: kSecClassKey,
    kSecAttrApplicationTag as String: "com.example.site.public",
    kSecReturnData as String: true
]

let qResult = SecItemCopyMatching(query as CFDictionary, &dataPtr)

// error handling with `qResult` ...

let data = dataPtr as! Data
let base64PublicKey = data.base64EncodedString()

请注意，数据大小为270，与密钥的块大小不同。在crypto.stackexchange.com上查看此问题。