![Bildschirmfoto 2017-07-01 um 00.00.56.png](https://steemitimages.com/DQmc3yv2FPQrDfPzBZJ8MCLYfjiEWU3D1D9jXRnPsqCM6un/Bildschirmfoto%202017-07-01%20um%2000.00.56.png) ***Note*** Each post I write, is building upon the stories from the articles before. Before reading the latest post I recommend to read through the prior posts again. You will get more confident with the technology behind cryptocurrencies, the more often you read through the articles and refresh your present knowledge. Take your time, to understand cryptocurrencies, it's worth it! If something in the article is not clear to you, don’t hesitate to ask. There are several persons who might have the same question. So don’t hesitate and comment, if something is unclear. Me and other readers will appreciate it! ----------------------------------------- So to some up the mathematical contest we talked about in the last posts: Alice (Miner) is participating in the Bitcoin-Park (Bitcoin-Network) in a mathematical contest in order to win a reward in Bitcoins. ![2.31.png](https://steemitimages.com/DQmXAMD5FNBzAyLVnNCoMWJcPPJParydYf4QMTEh3Zmoh3Q/2.31.png) In the [first post ](https://steemit.com/bitcoin/@manonlescaut/digital-signatures-in-bitcoin-payments-and-how-they-assure-that-only-you-have-control-over-your-bitcoins") I stated that there is actually another condition which has to be fulfilled by Alice (Miner), in order to get her reward. ![Bildschirmfoto 2017-06-30 um 23.32.55.png](https://steemitimages.com/DQmcBpcofybDgv1UkMZWgtbiLp8yVaQoxd2y4FNgaQzy2pg/Bildschirmfoto%202017-06-30%20um%2023.32.55.png) The other condition which has to be fulfilled by the miner is „SECURING THE Bitcoin-Network“. What does that exactly mean? Before we start the journey lets update the procedure of the mathematical contest with this new condition, which has to be fulfilled by Alice. ![2.3.3.png](https://steemitimages.com/DQmacQtQw6WSNcjLv34NRdkcp7uh4CVcLMopqEzTZ1T4iqC/2.3.3.png) How does Alice secure the Bitcoin-Network correctly in order to get her reward? And how can the visitors check if Alice secured the Bitcoin-Network in the right way? These are important questions we need to answer. So lets brake it down and start step by step. Lets take a closer look on the new condition; **Condition 2a: „Visitors check if Alice secured the Bitcoin-Network correctly“** To „secure the Bitcoin-Network“ Alice must make sure that nobody is stealing money or cheating in the Bitcoin-Network. So Basically after the visitors verified that the mathematical solution is correct, Alice must make sure that only Bitcoin-transactions are being executed, which are legitimate. Lets start with our analogy here: Imagine a normal Bitcoin-transaction: Bob sends Bitcoins to Charlie. The Bitcoins are now on the way from Bob to Charlie. Bob lives on the land and Charlie lives on an island. The only way for Bob to send these Bitcoins to Charlie is by boat. There is only one boat. This is where the „Alice secures the Bitcoin-Network“ starts. Alice is kind of the door staff of that boat and she decides which envelopes (Bitcoins-Transactions) can go on the boat and finally arrive at their destination on the island. ![2.3.4.png](https://steemitimages.com/DQmSazs1ZE93xsTQ8bTnugjRRoWoPEQYq3KKKmtX8uuDdJH/2.3.4.png) So Bob sent the envelope with Bitcoins on the way to Charlie. The envelope with Bitcoins arrives at the harbor and is queuing up in front of the boat. Alice is checking each envelope if they are legitimate. ![Bildschirmfoto 2017-06-30 um 23.47.10.png](https://steemitimages.com/DQmeYr6tM8i7W92vtphaUCsrjm24eSoV4BP7vecUrbPCVwE/Bildschirmfoto%202017-06-30%20um%2023.47.10.png) Alice must make sure that only valid envelopes are entering the boat. In [ the first post ](https://steemit.com/bitcoin/@manonlescaut/digital-signatures-in-bitcoin-payments-and-how-they-assure-that-only-you-have-control-over-your-bitcoins) I explained that only full,gapless envelopes (with Bitcoins) are legitimate. Take 5 minutes and read through [the first post](http://steemit.com/bitcoin/@manonlescaut/digital-signatures-in-bitcoin-payments-and-how-they-assure-that-only-you-have-control-over-your-bitcoins) again to refresh what you know so far… Well, Bob sent the Bitcoins in a valid, full gapless envelope, therefore Alice is letting this envelope on board. Everything is fine now… Well, not completely. Here we come to the second point which Alice has to take care of. Before sending the full envelope to Charlie, imagine Bob made a copy of that full envelope and sends it to another person, called David. Now there are exemplars of the same full gapless envelopes. This problem is called „Double spend-Problem“ in Cryptocurrencies. Bob wants to spend his Bitcoins twice by coping the full-envelope and just send the copy to another person. This has to be prevented by the miner (Alice) as well. So in order to „Secure the Bitcoin-Network“ correctly and receive the reward from the mathematical contest, Alice must take care of two things: 1. Only full,gapless envelopes enter the boat. ![Bildschirmfoto 2017-06-30 um 23.49.55.png](https://steemitimages.com/DQmdQY37BmT13V4JrbaDZ6NkVUnmA55igSdeYLsKGM5cLqs/Bildschirmfoto%202017-06-30%20um%2023.49.55.png) .2: There are no two exemplars of the same envelope on the boat. Remember [ the first post ](https://steemit.com/bitcoin/@manonlescaut/digital-signatures-in-bitcoin-payments-and-how-they-assure-that-only-you-have-control-over-your-bitcoins); Every full envelope has a unique pattern in the middle. You can easily identify if there are two envelopes with the same pattern. ![Bildschirmfoto 2017-06-30 um 23.51.28.png](https://steemitimages.com/DQmXS1bNa7FkiDRptHg2Ji8ks3TFNusCEZMjDjSzEUmNEhK/Bildschirmfoto%202017-06-30%20um%2023.51.28.png) After Alice filled the boat with envelopes, the visitors from the mathematical contest are coming on board and check what envelopes Alice let on the boat. If they find a non-gapless envelope (Not legitimate Transaction) or two exemplars of the same full envelope (Double-Spend), they will not allow the boat to take off. ![Bildschirmfoto 2017-06-30 um 23.54.22.png](https://steemitimages.com/DQmSdUwdm9ryGNChoBj9dgTdsvbjEDFoD9fN2hhSRT9QHYj/Bildschirmfoto%202017-06-30%20um%2023.54.22.png) In that case the payment-transactions on board are not getting executed, because they don’t reach their destination. If all envelopes on board are legitimate and there are no two exemplars of the same envelope, they will allow the boat to take off and reach their destination. So these transactions will be executed and are valid then. If the visitors approve that the transactions are legitimate the boat can take off. In that case Alice „secured the Bitcoin-Network“ correctly and finally receives her reward in Bitcoins. ***Summary*** Before miner gets the reward, the visitors check if the miner „secured the Bitcoin network“ correctly by letting only full gapless Envelopes (Legitimate Transactions) and there are no two exemplars of the same envelope on board (Double-Spend). The story is not over here, in the next article I will building up on that story today and we will get a clearer picture of the superior security in Bitcoin.