#define __NR_sysinfo 116
#include <sys/linux-syscalls.h> 

    .text 
    .type sysinfo, #function 
    .globl sysinfo 
    .align 4 
    .fnstart 

sysinfo: 
    .save   {r4, r7} 
    stmfd   sp!, {r4, r7} 
    ldr     r7, =__NR_sysinfo 
    swi     #0 
    ldmfd   sp!, {r4, r7} 
    movs    r0, r0 
    bxpl    lr 
    b       __set_syscall_errno 
    .fnend 

First, since the build-standalone-toolchain script of NDK (also included since r5) can only include stdc++ library into the toolchain it builds, compiling with STLport headers may lead to a list of build errors. In order to prevent this, using prebuilt compilers in the NDK (“the hard way” as described in readme) may be a better choice. In this case, you will have to take care with sysroot.

Second, developing with this special STLport has some limitations as mentioned in readme: Exception and RTTI are not supported. Remember to build every cpp source files with -fno-exceptions and -fno-rtti.

The steps are simple:

1. Download and install MacFUSE from here
2. Download and install NTFS-3G for Mac OSX from here
3. Restart your Mac
4. Enjoy~

	NSThread* myThread = [[NSThread alloc] initWithTarget:self selector:@selector(func_to_call:) object:param_to_func];
	[myThread start];

	[self performSelectorOnMainThread:@selector(func_in_main:) withObject:param_to_func waitUntilDone:YES];

Note: The above method should be compatible with iOS 3.x.

Update: One of my friends told me just now those beep sounds are called “beep code” and their meanings are dependent to different BIOS. A reference of Mac machines can be found here.
Update: Another reference in Wikipedia.

Compared with conventional broadcast encryption, attribute-based encryption is like separating users into different groups and the access control (using policy) is enforced by manipulating access controls in those groups. If the number of attributes is much less than the total number of users in the system, ABBE has a big advantage on efficiency. However, it cannot enforce ad-hoc access control on every individual user like conventional broadcast encryption.

Hence, some proposed using each bit of user ID as attribute, which makes the total number of attributes becomes log N (assuming N users). This number is much smaller than the total number of users and it sounds promising. However, during my study I found two major problems in this scheme when the number of legitimate users grows large.

First, in order to get a small ciphertext size, the scheme uses Boolean algebra simplification algorithm. The idea is to first list all user IDs of legitimate users in a truth table, then applies the simplification algorithm to get a shorter Boolean algebra expression without altering its result, and this problem is NP-Hard. The two most famous algorithms for this task are Quine-McCluskey algorithm and Espresso heuristic logic minimizer. The complexity of them is yet to be found, but according to my preliminary testing, the running time (for just Boolean algebra simplification) can be much longer than running encryption of Boneh’s broadcast encryption. A better simplification algorithm or a better implementation of it is required.

Second, the number of sum-of-product terms output from the simplification is not a constant. In other words, the ciphertext of this scheme will have a variable size. And this leads to a question: How large can the size be? I found it difficult searching for or understanding literature which discusses about this problem. Therefore, I try to run my own test again. I tried to compute both average case and worst case on small N (since I have to generate all combinations, it is already very large even for small N, e.g. 32). From my test, the growth of average size seems to be O(log N). For worst case, however, the size seems to be N/2. In my opinion, the problem is how often the size stays at O(log N). In real application, I think a good average bound is not enough, a good worst case bound is needed. Imagine when N = 10M, N/2 will be 5M and it results in a enormous ciphertext size.

謙讓語 (特別形):

丁重語 (特別形):

To obtain these two files, you may either Googling it online or if you have a Windows XP machine, you may find them in the following paths:

• C:\Program Files\Windows NT\hypertrm.exe
• C:\Windows\system32\hypertrm.dll

Copy both files to your Windows Vista/7 machine and remember to put them into the same directory.