Question

我一直在尝试使用Diffie Hellman密钥交换和椭圆曲线加密来加密和解密swift中的字符串。但是在密钥交换之后，我无法从CFData shared1 / shared2变量恢复私钥以进行解密。我得到的只是零值。

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, *) {
        guard let privateKey1 = SecKeyCreateRandomKey(attributes as CFDictionary, &error) else {return}

        let publicKey1 = SecKeyCopyPublicKey(privateKey1)
        guard let privateKey2 = SecKeyCreateRandomKey(attributes as CFDictionary, &error) else {return}

        let publicKey2 = SecKeyCopyPublicKey(privateKey2)

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

        guard let shared1 = SecKeyCopyKeyExchangeResult(privateKey1, SecKeyAlgorithm.ecdhKeyExchangeStandardX963SHA256, publicKey2!, dict as CFDictionary, &error) else {return}

        guard let shared2 = SecKeyCopyKeyExchangeResult(privateKey2, SecKeyAlgorithm.ecdhKeyExchangeStandardX963SHA256, publicKey1!, dict as CFDictionary, &error) else {return}

        print(shared1==shared2)
        let options: [String: Any] = [kSecAttrKeyType as String: kSecAttrKeyTypeEC,
                                      kSecAttrKeyClass as String: kSecAttrKeyClassPrivate,
                                      kSecAttrKeySizeInBits as String : 256]

        guard let key = SecKeyCreateWithData(shared1 as CFData,
                                             options as CFDictionary,
                                             &error) else {return}
        print(key)


        let str = "Hello"
        let byteStr: [UInt8] = Array(str.utf8)
        let cfData = CFDataCreate(nil, byteStr, byteStr.count)


        guard let encrypted = SecKeyCreateEncryptedData(publicKey1!,
                                                        SecKeyAlgorithm.eciesEncryptionStandardX963SHA256AESGCM,
                                                        cfData!,
                                                        &error) else {return}

        guard let decrypted = SecKeyCreateDecryptedData(key,
                                                        SecKeyAlgorithm.eciesEncryptionStandardX963SHA256AESGCM,
                                                        encrypted,
                                                        &error) else {return}




        print(decrypted)

    } else {
        print("unsupported")
    }

Answer 1

SecKeyFromData从该密钥的外部表示恢复密钥。您传递给它的值不是密钥的外部表示，它是一个共享机密（CFData）只是一些字节。您必须在共享机密上使用一些KDF派生密钥，然后才能将其用于加密和解密。

您用于加密和解密的密钥是错误的，您必须选择是否要进行非对称或对称加密。

SecKeyFromData： https://developer.apple.com/documentation/security/1643701-seckeycreatewithdata

使用安全框架快速加密

1 个答案: