//NSSecureCoding is the native binary
//serialization of objects
@interface Data : NSObject <NSSecureCoding>
@property (nonatomic) NSString *text;
@property (nonatomic) double num;
@end

@implementation Data

+ (BOOL)supportsSecureCoding {
    return YES;
}

- (void)encodeWithCoder:(NSCoder *)coder {
    [coder encodeObject:self.text
        forKey:@"text"];
    [coder encodeDouble:self.num
        forKey:@"num"];
}

- (instancetype)initWithCoder:
    (NSCoder *)coder {
    self = [super init];
    if (self) {
        _text = [coder
            decodeObjectOfClass:[NSString class]
            forKey:@"text"];
        _num = [coder
            decodeDoubleForKey:@"num"];
    }
    return self;
}
@end

Data *data = [Data new];
data.text = @"Hello";
data.num = 3.14;

NSData *bin = [NSKeyedArchiver
    archivedDataWithRootObject:data
    requiringSecureCoding:YES
    error:nil];
//bin.length bytes of binary plist