Lfsr 10 bitcoins
As privacy-enhancing authentications without any TTP Trusted Third Party , blacklistable anonymous credential systems with reputation have been proposed. However, the previous systems have the efficiency problem: The authentication data size is or , where L is the reputation list, and K is the size of a window indicating the most recent K authentications of the user. Therefore, the previous systems. The idea of aggregate signcryption was first proposed by Selvi. The aggregation process reduces the communication overhead and hence, it is efficient in low-bandwidth communication networks such as wireless sensor networks and vehicular ad-hoc network VANET. The goal of this study is to propose a secure provably identity based aggregate signcryption scheme ID-ASC without pairings over the elliptic.
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We need to create a random sequence to display to the player. Generating real random values for the LEDs is possible, though may be somewhat cumbersome as it means constantly generating random variables and storing them. Moreover, it is probably unnecessary. This is just a game, not some crazy bitcoin e-wallet that depends on true randomness to securely store all your money or something.
Introducing pseudorandomness! We can generate a sequence that looks seemingly random to the unsuspecting eye, but is generated using some sort of deterministic algorithm. The idea is using a shift register of certain length, and shift in the XOR of several bits from the shift register itself hence the feedback.
These bits are usually referred to as the LFSR taps. For an LFSR, initial state matters. All LFSRs output a constant stream of 0s when initially loaded with zeros.
But when loaded with anything else, a sequence of 1s and 0s will flow out. An LFSR is a finite automaton, thus can only output a finite stream of bits before it repeats itself. For further read, I can recommend the book ' mathematics - the man made universe ' by Sherman k. Stein, whose 8th chapter offers a different look on the subject of such maximal bit sequences, concerning medieval indian poetry rhythms.
How long will it take until the player would play the same game twice? That result is good enough for me - I don't suspect that any user will play that many game and also remember the sequence behind that. Moreover, I personally get bored after 20 games at most, usually far less. So it must be fine I guess. Comparing it to an 8 bit LFSR, the number of possible sequences is The game will probably begin to feel degenerated after 15 minutes of gameplay or so.
Notice that it's not what I have described before - this is a Galois LFSR, where the output get xored to multiple bits inside the shift register. I'll shortly explain why I chosen Galois LFSR, but for now it's enough to say that it's basic properties and behaviour remain the same. The polynomial should be maximal to get a full sequence - I just took the polynomial from the table in the wikipedia article for LFSRs, and briefly made sure that it is indeed maximal by simple enumeration of the outputs.
There isn't that much to it. The convenient way to shift them left as one long shift register is shifting each byte, using the C flag to hold the output of low byte and pass it to the higher byte.
After we shifted them all we're left with a feedback bit, now stored in the C flag. If C is 0, no action is needed and we immediately return. However if it is 1, the relevant mask must be xored to it. The brancing itself is made using the JNC opcode, which is quite useful for multi-byte logic.
The mask is stored as parameters which are used as immediate values. If we want to make it a little bit prettier, and we use global variables anywhere including registers , we can ditch some accumulator MOVs:.
Despite being elegant, notice the use of absolute IRAM addresses for r0 and r1 0x00 and 0x01 respectively - It might become a huge mess would I want to switch a register bank for example. This code portrays very well why I wanted a Galois LFSR rather than the 'regular' Fibonacci one - picking bytes one by one and xoring them together is uglier and more tedious to write - and far less convenient to change the tap values for than xoring whole bytes with constant masks.
The only catch is using a random seed, an initial value for the algorithm to use. Without it, Semyon will be a deterministic version of simon, which makes a very boring game.
Trust me. It means that I must have some source of randomness. One great such source is user input, or rather input timing. The player will never be able to click the buttons just at the same time since game over as in previous games - our clicking resolution is 10ms at best, while a counter can run as fast as the clock, around ns for instance. That's 5 orders of magnitude, plenty for random.
This is stressing it out though - a standard user will take seconds between games, as it looks to me. Nothing fancy here. The MCU runs now with a clock of There probably are ways which I don't know of to automatically count cycle duration of code, but for now let's count cycles manually. Given that after losing the user will probably take more than 1 second to start a new game, this way to update the LFSR should span the whole seed-value range very well, with uniform-enough probability to get each seed.
I'll call it random! I always hate this part of such projects. If you never used them yet, know that tactile buttons are not very reliable - the physical contact tend to jump and vibrate, which can generate multiple click signals for the MCU input.
One way to solve it is connecting capacitors in parallel to the buttons and call it a day - they will low-pass-filter any pesky button bounce. It makes sense when using discrete logic, but that's just lame when one has a full MCU to solve his problems. Thus I pulled out the vanilla way to debounce, which is simply adding delays.
Additionally, though it doesn't matter for this project, conditional jumps on bits e. This makes bitwise GPIO addressing quite pointless in my eyes. This is a lesson learned - Bit operations are worth using only in specialized cases which deserve it. It might be a time-sensitive operations regarding a port e. One exception to this: operations on the C flag are still very useful for multi-byte arithmetic and logic.
Last note about that - the code came out like some nasty version of arduino code, using these digitalRead wraps that work on one bit of the GPIO port registers at a time. I don't like using the arduino, somewhat for the lack of elegance and compactness of exactly such situations - Now doing so in assembly feels sevenfold worse and ugly. Nothing to behold. The clumsy use of bit operations once again shows that it wasn't a good idea to work that way. Here's a hypothetical way to make it much better by using regular byte operations:.
Anyway as mentioned earlier, the whole code can be found in the git repository. Create an account to leave a comment. Already have an account? Log In. Yes, delete it Cancel. About Us Contact Hackaday. By using our website and services, you expressly agree to the placement of our performance, functionality, and advertising cookies. Learn More. Sign up Log in. My name is Random, Pseudo Random We need to create a random sequence to display to the player. Are 16 bits enough?
Thus come initialization state of the game: initialize: ;This is the initialization phase of semyon. Let's see if it makes sense. Given period of the LFSR, one should get: Given that after losing the user will probably take more than 1 second to start a new game, this way to update the LFSR should span the whole seed-value range very well, with uniform-enough probability to get each seed. User input and debouncing I always hate this part of such projects.
I'm not proud of code you're about to see. But this thing works, anyway. That's the code basically. These two logs got mush longer than I expected. For me, this preliminary version of Semyon was very educating, and I hope it was for you too :. Become a Hackaday. Sign up. Ok, I agree.
Introduction to Cryptography with Coding Theory, 3rd edition
Set nonce generator. Notwithstanding, in an expert chosen cryptographic protocol as assumed in the question it will be more common for both parties to choose a nonce, mitigating inadequate choice of a nonce by only one party. Set "ScriptNonce", nonce ; context. If you are writing low-level code that retrieves or uses these tokens, it's important to validate the tokens before you trust them.
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It makes me sad that all this computation can't simultaneously be used to fold proteins, or some other "externally productive" calculation. The work done has to be specifically tied to the previous block on the blockchain made of up transaction data, which is of course unrelated to proteins or anything else "useful" in the view of the questioner. Otherwise, you cannot demonstrably prove the integrity of the blockchain. The short answer is: they are doing useful work -- they're securing an increasingly large and distributed financial network. There are alternatives to hashing proof-of-work. Peercoin's security comes from the developer of the system signing every block. It attempts to use a "Proof of Stake" system where ownership of coins controls mining, but the problem with PoS is, ironically, that there is nothing at stake.
We need to create a random sequence to display to the player. Generating real random values for the LEDs is possible, though may be somewhat cumbersome as it means constantly generating random variables and storing them. Moreover, it is probably unnecessary. This is just a game, not some crazy bitcoin e-wallet that depends on true randomness to securely store all your money or something.
A linear-feedback shift register LFSR is a method of manipulating a number a register by shifting it moving all the bits to the left or right and then adding a new bit in the space that was created the feedback. The initial state is called the seed, and because an LFSR is deterministic it will always generate the same number sequence when starting from a given initial state. The feedback works by taking certain bits called taps and combining them using XOR to generate the bit which will be inserted into the gap created by the sift. An example of a simple 4 bit LFSR is to use bits 3 and 4. These are combined using XOR and inserted into bit 1, after it has been shifted to the left.
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