如何在 IOS Swift 中使用来自服务器的公钥生成 ECDH 键值对？

Question

我尝试用ECDH生成键值对，我成功生成了两个键值对。通过两对，我生成了一个共享密钥，并且工作正常。但是当我尝试使用来自服务器的公钥创建共享密钥时，我做不到。来自服务器的公钥是十六进制格式。我无法将十六进制值转换为公钥 (secKey)。

生成两个键值对和两个共享秘密的代码：

var error: Unmanaged<CFError>?
        let keyPairAttr:[String : Any] = [kSecAttrKeySizeInBits as String: 256,
                                          SecKeyKeyExchangeParameter.requestedSize.rawValue as String: 32,
                                          kSecAttrKeyType as String: kSecAttrKeyTypeECSECPrimeRandom,
                                          kSecAttrKeyClass as String: kSecAttrKeyClassPublic,
                                          kSecPrivateKeyAttrs as String: [kSecAttrIsPermanent as String: false],
                                          kSecPublicKeyAttrs as String:[kSecAttrIsPermanent as String: false]]
        let algorithm:SecKeyAlgorithm = SecKeyAlgorithm.ecdhKeyExchangeStandardX963SHA256 //ecdhKeyExchangeStandardX963SHA256

        do {
            guard let privateKey = SecKeyCreateRandomKey(keyPairAttr as CFDictionary, &error) else {
                throw error!.takeRetainedValue() as Error
            }
            let publicKey = SecKeyCopyPublicKey(privateKey)

 guard let privateKey2 = SecKeyCreateRandomKey(keyPairAttr as CFDictionary, &error) else {
                throw error!.takeRetainedValue() as Error
            }
let publicKey2 = SecKeyCopyPublicKey(privateKey2)
           

let shared:CFData? = SecKeyCopyKeyExchangeResult(privateKey, algorithm, publicKey2!, keyPairAttr as CFDictionary, &error)
            let sharedData:Data = shared! as Data
            print("shared Secret key",sharedData.base64EncodedString())

            let shared2:CFData? = SecKeyCopyKeyExchangeResult(privateKey2, algorithm, publicKey!, keyPairAttr as CFDictionary, &error)
            let sharedData2:Data = shared2! as Data
            print("shared Secret key 2",sharedData2.base64EncodedString())

if sharedData.base64EncodedString() == sharedData2.base64EncodedString() {  
                let secretKey = sharedData.base64EncodedString()
                print("SEC KEY MATCHES",secretKey)
}

上面的代码是有效的，因为我自己创建了两个键值对。但我无法使用服务器的公钥创建它。 我需要知道如何使用十六进制格式的服务器公钥创建共享密钥。

Answer 1

kSecAttrKeySizeInBits 作为字符串：256 256应该是384