Abstract definition: A Hash Time Locked Contract ( HTLC ) is a type of script that a sender can lock funds in with two payment routes. Either the redeemer provides something that unlocks the first payment route, or the first payment route “times out” and the second payment route is exposed to the sender, who then has the option of taking back her funds.

We’ll dive deeper into this. But first, what could this be used for?

HTLCs hold utility for a plethora of reasons — but mainly because they allow for trustless escrow within a standard* bitcoin transaction.

Some…


Fold provides a few different payment methods that offer up to 20 percent back in bitcoin on your purchase. Below are the payment methods offered along with the platform supported.

  • Credit Card (Mobile)
  • Bitcoin (Web)
  • Lightning (Mobile and Web)

What is Lightning

Lightning is short for The Lightning Network, which is a quicker way to pay someone with Bitcoin. Bitcoin is great, however its common pain points are that it can have expensive fees and slow wait times.

We love Bitcoin, but this can create a tough experience for our customers. Lightning doesn’t have these issues — where Bitcoin transacting is slow and…


Credit: buybitcoinworldwide

Warning: This article is not for beginners. It will explore HD wallets, how they’re built, and how to use them in Bitcoin.

This article will be relevant across Bitcoin, Bitcoin Cash, and all other forks of Bitcoin that still hold “Bitcoin” in the name.

What exactly is an HD wallet?

If you find yourself asking this, please consult my other articles HD Wallets Explained and this article’s sister So you want to build an Ethereum HD wallet?

How to Build a Bitcoin HD Wallet in node.js

Now you should know what an HD wallet is and that it’s really a tree of nodes, each with a private and public key. First what we’ll do is…


Got an interview coming up for a crypto interview? Here’s a short list of facts and explanations I’ve come up with while preparing for my series of interviews.

This article is a constant work in progress, and additions will be made as time progresses or as proposed.

Bitcoin Transactions

  1. Can be comprised of many inputs and outputs
  2. The inputs are the previous transaction hash and the index of the previous transaction output which you want to spend
  3. Each output are values assigned to an address
  4. In general, a transaction is expected to have 2 outputs, the destination address and the change address


Credit: Prooworld

Warning: This article is not for beginners. It will explore HD wallets, how they’re built, and how to use them in Ethereum.

What exactly is an HD wallet?

Hierarchical Deterministic Wallets (or HD wallets for short) were introduced by BIP 32 and later improved by BIP 44. BIPs (if you’re not familiar with them) stand for Bitcoin Improvement Proposal. Why are we talking about Bitcoin right now? You should take a look at The History of the space for context. Although the Bitcoin and Ethereum networks are incredibly different today, there are still a lot of similarities to be found between the two currencies. …


This article is not intended for beginners in the crypto space. It is an in-depth analysis on the structure and usage of an HD Wallet for developers.

Hierarchical Deterministic Wallets (or HD wallets for short) were introduced by BIP 32 and later improved by BIP 44. BIPs (if you’re not familiar with them) stand for Bitcoin Improvement Proposals. While HD wallets were introduced by the Bitcoin community, it is a wallet structure that supports many coins. HD wallets can allow for an entire suite of crypto-wallets to be generated from a single seed phrase, although not a commonly used feature.


Credit: yeeply.com

For the last year it’s been Blockchain, Blockchain, Blockchain! It’s a word we all started hearing around the end of 2017 when Bitcoin began it’s steep climb to it’s all time high of $20,089 per token. But does it also revolutionize the supply chain industry? There are plenty of companies that have come out with ‘revolutionizing’ technologies centered around blockchain that are designed to revamp an industry be it ARVR, healthcare, or supply chain infrastructures. But what are some use-cases for blockchain in the supply chain infrastructure?

I’ve spent the past few weeks researching this question for a client. This…

Harsha Goli

Former fold, bitpay Engineer

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