- (NSData *)getKey {
    // Identifier for our keychain entry - should be unique for your application
    static const uint8_t kKeychainIdentifier[] = "io.Realm.EncryptionExampleKey";
    NSData *tag = [[NSData alloc] initWithBytesNocopy:(void *)kKeychainIdentifier
                                               length:sizeof(kKeychainIdentifier)
                                         freeWhenDone:NO];

    // First check in the keychain for an existing key
    NSDictionary *query = @{(__bridge id)kSecclass: (__bridge id)kSecclassKey,(__bridge id)kSecAttrApplicationTag: tag,(__bridge id)kSecAttrKeySizeInBits: @512,(__bridge id)kSecReturnData: @YES};

    CFTypeRef dataRef = NULL;
    Osstatus status = SecItemcopyMatching((__bridge CFDictionaryRef)query,&dataRef);
    if (status == errSecSuccess) {
        return (__bridge NSData *)dataRef;
    }

    // No pre-existing key from this application,so generate a new one
    uint8_t buffer[64];
    status = SecRandomcopyBytes(kSecRandomDefault,64,buffer);
    NSAssert(status == 0,@"Failed to generate random bytes for key");
    NSData *keyData = [[NSData alloc] initWithBytes:buffer length:sizeof(buffer)];

    // Store the key in the keychain
    query = @{(__bridge id)kSecclass: (__bridge id)kSecclassKey,(__bridge id)kSecValueData: keyData};

    status = SecItemAdd((__bridge CFDictionaryRef)query,NULL);
    NSAssert(status == errSecSuccess,@"Failed to insert new key in the keychain");

    return keyData;
}

我正在努力将此应用程序转换为Swift,我正在尝试使用Realm的快速代码示例检索存储在Keychain中的加密密钥

func getKey() -> NSData {
    // Identifier for our keychain entry - should be unique for your application
    let keychainIdentifier = "io.Realm.EncryptionExampleKey"
    let keychainIdentifierData = keychainIdentifier.data(using: String.Encoding.utf8,allowLossyConversion: false)!

    // First check in the keychain for an existing key
    var query: [Nsstring: AnyObject] = [
        kSecclass: kSecclassKey,kSecAttrApplicationTag: keychainIdentifierData as AnyObject,kSecAttrKeySizeInBits: 512 as AnyObject,kSecReturnData: true as AnyObject
    ]

    // To avoid Swift optimization bug,should use withUnsafeMutablePointer() function to retrieve the keychain item
    // See also: https://stackoverflow.com/questions/24145838/querying-ios-keychain-using-swift/27721328#27721328
    var dataTypeRef: AnyObject?
    var status = withUnsafeMutablePointer(to: &dataTypeRef) { SecItemcopyMatching(query as CFDictionary,UnsafeMutablePointer($0)) }
    if status == errSecSuccess {
        return dataTypeRef as! NSData
    }

    // No pre-existing key from this application,so generate a new one
    let keyData = NSMutableData(length: 64)!
    let result = SecRandomcopyBytes(kSecRandomDefault,keyData.mutableBytes.bindMemory(to: UInt8.self,capacity: 64))
    assert(result == 0,"Failed to get random bytes")

    // Store the key in the keychain
    query = [
        kSecclass: kSecclassKey,kSecValueData: keyData
    ]

    status = SecItemAdd(query as CFDictionary,nil)
    assert(status == errSecSuccess,"Failed to insert the new key in the keychain")

    return keyData
}

现在的问题是Swift代码无法通过Objective-C代码返回存储在Keychain中的值.我在创建keychainIdentifierData时尝试修改Swift代码以使用NSData而不是Data,但我无法让它工作.

在我的实际项目中,SecItemcopyMatching调用返回成功状态,但dataTypeRef始终为nil,在强制转换为Data时崩溃.在我为此创建的一个小测试项目中,找不到密钥,这似乎表明问题在于将keychainIdentifier转换为keychainIdentifierData,但我现在找不到任何信息如何在语言之间保持一致.

我发现的一个线索是将标签/ keychainIdentifierData打印到控制台,在Obj-c中它是
< 696f2e52 65616c6d 2e456e63 72797074 696f6e45 78616d70 6c654b65 7900>
在斯威夫特的哪个地方
< 696f2e52 65616c6d 2e456e63 72797074 696f6e45 78616d70 6c654b65 79>

这表明密钥在语言之间不匹配,但后来我不明白为什么SecItemcopyMatching会返回成功.

有没有人对如何检索我的加密密钥有任何见解？提前致谢 ：)

要实现奇偶校验,请在创建Objective-C标识符时省略最后一个字符：

static const uint8_t kKeychainIdentifier[] = "io.Realm.EncryptionExampleKey";
NSData *tag = [[NSData alloc] initWithBytesNocopy:(void *)kKeychainIdentifier
                                           length:sizeof(kKeychainIdentifier) - 1 // <- Truncate last char
                                     freeWhenDone:NO];

或者,使用Nsstring在Objective-C中表示您的标识符：

Nsstring *keychainIdentifier = @"io.Realm.EncryptionExampleKey";
NSData *tag = [keychainIdentifier dataUsingEncoding:NSUTF8StringEncoding];

{
    "myobj" : {
        "objList" : [
            { "location" : "Texas" },{ "location" : "Houston"},{ "name":"Sam" }
        ]
    },"category" : "cat1"
}


{
"myobj" : 
{
    "objList" : [
        { "location" : "Tennesy" },{ "location" : "NY"},{ "location" : "SF" }
    ]
},"category" : "cat2"

}

我想提取位于“休斯顿”的“**类别**”.在简单的JSON对象的情况下,我必须将其作为查询传递,如：

BasicDBObject place = new BasicDBObject();
place.put("location","Houston");

但是在嵌套JSON的情况下,我不知道如何将其作为查询传递并获得适当的类别.即如果我将我的位置作为“休斯顿”通过,那么它应该返回它的相应类别“cat1”…我希望我的问题现在清楚了….

db.coll1.insert({
    "myobj" : {
        "objList" : [
            { "location" : "Texas" },"category" : "cat1"
})

和

db.coll1.insert({
    "myobj" : {
        "objList" : [
            { "location" : "Tennesy" },{ "location" : "SF" }
        ]
    },"category" : "cat1"
})

现在您可以使用dot operator找到您想要的内容：

db.coll1.find({“myobj.objList.location”：“Texas”}).pretty()将返回一个具有德克萨斯州的对象

db.coll1.find({“myobj.objList.location”：“SF”}).pretty()将返回一个具有SF的对象

db.coll1.find({“myobj.objList.location”：“Houston”}).pretty()将返回两个对象

现在我希望你能用Java编写它.我从来没有使用过Java,但based on this question你可以做这样的事情.如果它不起作用,只需看看如何在java驱动程序中使用dot运算符为mongo：

DBCursor cursor = coll1.find(new BasicDBObject("myobj.objList.location","Texas"));

附：你说,你想要检索类别.以这种方式,您将需要使用投影db.coll1.find({<我提供的查询},{category：1,_id：0})