ios - ios/swift 中的椭圆曲线 Diffie Hellman

Question

iOS 是否公开用于 key 生成的 API 以及使用 ECDH 的 key 派生？

据我所知，苹果正在内部使用它(特别是 x25519)，但我没有看到它通过通用加密或其他方式公开为公共(public) API。

谢谢，

Z

Answer 1

在 Playground 上使用 Xcode 8.3.3 完成，使用 EC 为 Alice、Bob 生成私钥/公钥，然后使用 Alice 的私有(private) key 和 Bob 的公共(public) key 计算 Alice 的共享 key ，并使用 Bob 的私有(private) key 和 Alice 的公共(public) key 为 Bob 计算共享 key 并最终断言它们是相等的。

import Security
import UIKit

let attributes: [String: Any] =
    [kSecAttrKeySizeInBits as String:      256,
     kSecAttrKeyType as String: kSecAttrKeyTypeEC,
     kSecPrivateKeyAttrs as String:
        [kSecAttrIsPermanent as String:    false]
]

var error: Unmanaged<CFError>?
if #available(iOS 10.0, *) {
    // generate a key for alice
    guard let privateKey1 = SecKeyCreateRandomKey(attributes as CFDictionary, &error) else {
        throw error!.takeRetainedValue() as Error
    }
    let publicKey1 = SecKeyCopyPublicKey(privateKey1)

    // generate a key for bob
    guard let privateKey2 = SecKeyCreateRandomKey(attributes as CFDictionary, &error) else {
        throw error!.takeRetainedValue() as Error
    }
    let publicKey2 = SecKeyCopyPublicKey(privateKey2)

    let dict: [String: Any] = [:]

    // alice is calculating the shared secret
    guard let shared1 = SecKeyCopyKeyExchangeResult(privateKey1, SecKeyAlgorithm.ecdhKeyExchangeStandardX963SHA256, publicKey2!, dict as     CFDictionary, &error) else {
        throw error!.takeRetainedValue() as Error
    }

    // bob is calculating the shared secret
    guard let shared2 = SecKeyCopyKeyExchangeResult(privateKey2, SecKeyAlgorithm.ecdhKeyExchangeStandardX963SHA256, publicKey1!, dict as CFDictionary, &error) else {
        throw error!.takeRetainedValue() as Error
    }

    print(shared1==shared2)


} else {
    // Fallback on earlier versions
    print("unsupported")
}

感谢@Mats 指引我正确的方向..3