Build an automatic escrow service

Hello. I want to build a website, that will act as a "middleman" or "escrow" for two know cryptocurrencies, so knowledge about this subject is highly recommended, even mandatory. Most trades are usually made man-to-man, which makes it difficult most of the times, where people might scam you, take your money and theirs, waste your time, etc.. The website will make both the clients put their trust into a machine which only job is to securely verify and send the money to both parties, taking a commission fee. The currencies used will be : *Stellar : [login to view URL] From this, you will need the commands that will verify transactions, and automatically send money to X address. *Bitcoin : [login to view URL] From this, you will simply need the command that verifies if a X transaction is requested. The steps the website will follow are all described in the pictures below (This is the simplest and most detailed explanation i could come with in 5 minutes. I CAN make a detailed .psd, but i'm mainly looking for the script, it's just that there is no script section in freelancer.com) The 1-2-3 pictures are seen by the seller, and the 1-1.2.3 pictures are seen by the buyer.