Gapcoin Cryptocurrency: A Peer-to-Peer Electronic Cash System

New! Gapcoin Core 2606

We have been working on a new version of Gapcoin Core to revitalize the Gapcoin Network with modern and much improved code that is easier to build and run on current systems, and hard coded reliable nodes we provide. Since there were many changes from 0.16.3, precautions must be taken when upgrading. Please read the upgrade notes below.

• Source Code: https://github.com/PrimesClub/Gapcoin
• Binaries: Windows x64 (Setup), Linux x64, Linux Arm64

Important! Upgrade Notes

Tldr: highlighted text

• Gapcoin Core 2606 is based on Riecoin Core 2606 which we also maintain, and is itself based on Bitcoin Core 31.x. Putting in common Riecoin and Gapcoin Development shall benefit both Projects. There were countless improvements since 0.16.3, including soft forks and wallet format change. Considering that the network is currently quite weak anyway and barely used, we propose to not bother with some Activation process such as Bip9 and directly enable support of the new Bitcoin features with 2606.
  • Avoid using Exchanges until they upgraded to 2606. Or, ensure that you hold funds with Legacy Addresses generated with getnewaddress "" legacy.
  • Forks may theoretically happen due to some differences introduced over years by Bitcoin or Riecoin, though unlikely due to the lack of incentives to mess with Gapcoin's Blockchain, and even if they happen, not much is at stake anyway. Again, considering the weakness of the network, we think that it is the most reasonable way to perform such an upgrade after years or stale development. Regularly monitor Gapcoin.club to check if something happened and requires action.
• 0.9 and 0.16 Wallets are incompatible with 2606 due to the switch from Legacy to Descriptor Wallets. The Data Folder has moved (~/.gapcoin2606 instead of ~/.gapcoin on Linux for example). So when you start Gapcoin 2606, you will not see your funds, this is normal.
• The Blockchain should be redownloaded from scratch. Nodes and Checkpoints are hardcoded for a reasonably quick initial sync. It also is possible to copy old Blockchain files to the 2606 folder and accept to "reindex" as an error message appears on opening Gapcoin 2606, but we still advise to redownload from scratch.
• Move your funds from the old wallet to the new wallet, or send everything to an Exchange you trust. To move funds,
  • With the 2606 version, create a Wallet and then a Legacy Address (G..., not gap1...): open the Console and run getnewaddress "" legacy to generate one.
  • Then, from the old Version, send all your funds to that Legacy Address (or test first with a very small amount to be sure that it goes through).
• Keep your old version until you transferred all your funds and are certain that everything is fine with 2606.
• It is a Development Version, but we are confident that it is reliable enough for production use.
• We have not ported the GUI additions made for 0.16.3 as we deem that it would be more appropriate to offer those in separate software.

Other Software

• Separate Miners: GapMiner (Benxy031 Fork)

What is Gapcoin?

Gapcoin is a prime number based P2P cryptocurrency, inspired by the two previous scientific currencies Primecoin and Riecoin. It's a code fork of Satoshi Nakamoto's Bitcoin, a decentralized payment system which is independent of banks, governments and other centralized regulators. With Gapcoin, you can send money around the globe in seconds. The big improvement in comparison to Bitcoin is that instead of burning electricity for it's own sake, Gapcoins Proof of Work function actually does useful work by searching for large prime gaps.

Specifications

• PoW: Prime Gaps
• Block target time 2.5 minutes: 4x faster transaction confirmations than Bitcoin!
• Block reward proportional to the current difficulty
• Block reward halving every 420000 (about 2 years)
• Cap: about 18-20 million GAP
• Difficulty adjusts every block and increases logarithmically

Fair launch

Gapcoin was not designed to enrich the early adopters or the coin creators, there wasn't any premine! To avoid instamine, the reward of the first 1152 blocks (about 48 hours) increased quadratically to it's absolute value: the current difficulty. The block reward was 1/1152^2 * blockheight^2 * difficulty for the first 1152 blocks. The source code was made available before launch (excluding the PoW function), so that everyone could setup their own testing environment, compile the software, and check that everything works. Windows and Linux binaries were distributed in an encrypted container before launch, the password was revealed at launch on Tue Oct. 21 2014 - 18:00:00 UTC"

Gapcoin FAQ

Source for most of this section: The Original Gapcoin website gapcoin.org

How is Proof of Work actually designed?

A PoW algorithm has to fit two specifications:

• It must be cryptographically secure (a PoW must not be reusable)
• It must be hard to calculate, but easy to verify

Verifying a prime gap is easy, you only have to check every number between the start and the end to be composite. Calculating is harder, much harder! Large prime gaps occur a lot lesser than smaller ones. According to E. Westzynthius, in e^n prime gaps there will be one gap that is n times greater than the average prime gap."

So the difficulty will simply be the length of the prime gap?

Not exactly. The average length of a prime gap with the starting prime p, is log(p), which means that the average prime gap size increases with larger primes. So one could simply choose p as large as possible and gaps will also often be very large. So, instead of the pure length, we use the merit of the prime gap, which is the ratio of the gap's size to the average gap size. In other words we are looking for gaps that are particularly large for a given number.

Let p be the prime starting a prime gap, then m = gapsize/log(p) will be the merit of this prime gap.

Also a pseudo random number is calculated from p to provide finer difficulty adjustment.

Let rand(p) be a pseudo random function with 0 < rand(p) < 1. Then, for a prime gap starting at prime p with size s, the difficulty will be s/log(p) + 2/log(p) * rand(p), where 2/log(p) is the average distance between a gap of size s and s + 2 (the next greater gap) in the proximity of p.

When it actually comes to mining, there are two additional fields added to the Blockheader, named “shift” and “adder”. We will calculate the prime p as sha256(Blockheader) * 2^shift + adder. As an additional criterion the adder has to be smaller than 2^shift to avoid that the PoW could be reused."

Could we break any world records?

In 2017 (confirmed in early 2018) the Gapcoin network found a new prime gap of maximum known merit! The merit M=G/ln(P1) of this gap is M=41.93878373153988, the largest merit of any known prime gap, and the first prime gap to be discovered with a merit exceeding 40. Source : https://faculty.lynchburg.edu/~nicely/

We already broke more than 544 records of first known occurrence prime gaps. (Note: New record data to be updated from the blockchain).

Also, if the difficulty reaches 41.94, every block will be a new world record!"

Gapcoin's highest found merits as of 10th September 2019 (Top 30)

• http://gapcoin.org/primegaps-merits.php
• https://web.archive.org/web/20200219231207/http://gapcoin.org/primegaps-merits.php

Does Gapcoin have a Whitepaper?

The original developer did not produce a whitepaper for Gapcoin.

We recommend that you read the original Bitcoin whitepaper and realize that Gapcoin is effectively Bitcoin featuring the above mathematically functional proof-of-work "bells and whistles" optimizations.

But how are prime gaps useful?

Prime numbers are interesting for lots of mathematicians around the globe, and they're also important to every day cryptography (see RSA).

Researches about prime gaps could not only lead to new breakthroughs in the bounded gap, it may also help proving the Twin Prime Conjecture and maybe even the millennium problem, the Riemann hypothesis. Who knows?

What are the differences between Primecoin, Riecoin and Gapcoin? Which one should I choose?

The PoW criteria is of course the main difference between the currencies. Primecoin is based on Cunningham chains, and Riecoin's PoW is kind of the opposite of Gapcoin's as they are looking for Prime Constellations or k-tuplets, which are group of k prime numbers that are as close as possible. Prime Gaps have a very minor technical advantage as it is more straightforward to design Mining Pools, which can also be more flexible.

The coin emission is another major difference. Nowadays Primecoin emits the most coins daily due to the lack of a halving mechanism, also meaning that the supply is uncapped. Riecoin has a halving mechanism similar to Bitcoin's, with a practical supply cap of about 72 millions RIC. Gapcoin also halves, but once every 2 years instead of 4, making it the scarcer one with a supply cap of about 20 millions GAP. On the other hand it also means less rewards for miners.

But fundamentally, the underlying principles remain the same. In fact, there is nothing preventing all three PoWs from being implemented together into a single Currency and it is unfortunate that the creators of the three Currencies did not collaborate to extend Primecoin's PoW to also accept k-tuplets and gaps, and rather chose to create their own Currency, resulting on three split communities despite the common desire to make the PoW energy consumption more useful to society.

If that is also your desire, then you should support all three Currencies, convince anyone mining other coins to stop mining hashes and come mine XPM, RIC or GAP instead, and also call for the three Projects to unite forces. It is advisable to buy and hold RIC or GAP rather than XPM due to Primecoin's higher emission rate and unlimited supply.

Prime Gap Resources