Crypto and international payments

What a cryptocurrency actually is

A cryptocurrency is not something stored on your phone; it is a row in a ledger that thousands of independent computers each keep a copy of, and owning it means holding the private key that can authorise moving that row. The same two properties that make this work, no institution in the middle and no way to reverse a transfer, are both its biggest advantage and its biggest danger.

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Six properties, all from one decision

That one decision is to have no institution in the middle. The first four get advertised; the last two are where people get hurt.

Crypto a row in a shared ledger
  • Shared ledger
  • Your key, your money
  • Borderless
  • Supply by rule
  • Irreversible
  • Volatile

These six are about the technology, not about value. None of them says a particular coin is good or bad, and neither do we.

Last checked: Facts and tool names in this lesson are re-checked against their sources on this date.

So what is a cryptocurrency, exactly?

A cryptocurrency is a row in a ledger. The ledger does not sit on a particular server; thousands of independent computers each hold a full copy of it and all of them have agreed on one rule for what counts as a valid change. When somebody says a person has ten units, it means there is a row in that ledger saying so.

So what is on your phone? A key. Not money, not a file, not anything you could copy. A wallet holds only the private key, and what that key does is sign one instruction: move this row to that address. The network checks the signature and, if it holds, the ledger changes.

The word coin is the most misleading word in the whole subject and it sends people looking for an object that does not exist. Nothing is moved. If only one sentence from this lesson stays with you, make it this one: you do not hold the coin, you hold the permission to move it.

The immediate consequence is that losing a key resembles losing a bank password in no way at all. There, your identity backs the password and it can be recovered; here, the key is the only thing there is. The shared ledger and the network that keeps it are the subject of the next lesson in this path, and how thousands of independent computers are connected at all is opened up in the internet and networks path.

Thousands of identical glass ledgers orbiting one white entry with a small key at the centre

What separates it from money in a bank?

Four things, and all four come from one design decision: there is no institution in the middle. The founding document of the idea was published in 2008 and its first sentence says exactly that, that the point is to let a payment go straight from one party to another without going through a financial institution.

First, nobody grants permission. No account is opened because there is no account; you generate a key pair and that is all. Second, a transfer to the other side of the world and one to the next town are the same job to the network. Third, supply is set by a rule rather than by a decision; every network has its own rule, that rule is written in code and the code is public. Fourth, the ledger is public, so you need not believe anybody, you can look for yourself.

Now the other side of the same coin, the side the advertising tends to leave out. The institution that is not in the middle is the same institution that does something for you when you make a mistake. A transfer sent to a wrong address does not come back: no branch, no dispute form, no number to call. And a fraud you approved yourself is, from the network point of view, a perfectly valid transfer.

Take that symmetry seriously, because it is the whole difference between somebody who works with crypto comfortably and somebody who loses their money. The advantage and the danger are not two separate things you could keep one of and drop the other; they are one property seen from two sides. The fuller bank-versus-crypto comparison belongs to the international payment lesson later in this path, because that is where the real choice sits.

No institution in the middle: what it gives, it also takes

The two pans here are not two separate properties. They are one property seen from two sides.

What it gives

  • Nobody grants permission, so nobody can take it back either.
  • A transfer across the world and one to the next town are the same job.
  • Supply is set by a rule, not by the decision of a meeting.
  • The ledger is public; you need not take anybody word for it.

What it takes

  • A transfer to a wrong address does not come back: no branch, no dispute form.
  • A lost key means lost money, and there is no identity recovery.
  • A fraud you approved yourself is, to the network, a valid transfer.
  • No institution holds the price, and there is no ceiling on the swing.

This balance is not level and is not meant to be. Which side weighs more for you depends on what you are doing, and nobody but you can answer that.

How is Bitcoin different from all the others?

The right question is not which coin, it is which network. Some of these have a network of their own and some are only a contract sitting on somebody else network, and that difference decides where your money travels, what you pay the fee in, and whether it arrives at all.

Bitcoin has its own network; so do Ethereum and Tron. Tether does not. Tether is a contract published on other networks, and that is what makes one name into several different things. We are not repeating this from somebody else: we are reading it off our own code. The payment system on this site knows Tether on Tron and Tether on BNB Smart Chain as two separate assets, with two address formats, two decimal counts and two confirmation policies.

How separate? Separate enough that our system cannot build an invoice at all until it knows both which coin and which network. The address format, the counting unit and the confirmation policy all hang off that one choice, and not one of the three is the same between those two rows. Exactly what differs and which network to pick is the subject of the networks and fees lesson in this path, where it is opened up with numbers and sources.

The practical result for somebody who wants to be paid is this: when a client says they are sending Tether, nothing has been settled yet. The question to ask is which network, and the address you hand over has to be an address on that same network. Sending on the wrong network is one of the commonest ways to lose money and it has nothing to do with fraud; two leading characters of an address were simply not the same.

A coin with its own network, or a token on another network

Neither is better than the other; they are two different things. Confusing them is what destroys money.

A coin with its own network

  • Its rules are set by that network and it lives nowhere else.
  • You pay the fee in that same coin.
  • Examples: Bitcoin, Ethereum, Tron.
  • If the network stops, the coin itself has stopped with it.

A token on somebody else network

  • It is a contract published on another network infrastructure.
  • You pay its fee in the host network coin, not in the token.
  • Example: Tether, published on several networks at once.
  • One name on two networks is two things, and they do not transfer between each other.

The examples are there to show the difference and are not a recommendation. Which one you accept is between you and the other side, and this page does not intervene.

Why is volatility the risk that matters?

Because between the moment you agree an amount and the moment that amount arrives, it may no longer be that amount. For somebody collecting a fee for work this is a settlement problem, not an investment problem, and that distinction shapes this whole path.

We do not argue this in the abstract; we solved it in our own code and the number is there to be read. When somebody tops up their wallet on our site with crypto, the invoice is built at a rate and that rate stays valid for exactly 90 minutes; window_min in our configuration is that number. We did not pick 90 minutes because it looks tidy, it is the longest we are willing to stand behind a price. All four invoices sitting in our table today are marked expired, meaning the user did not pay inside that window and the invoice had to be built again.

Notice that none of this is a statement about a price going up or down, and we have no view on that and offer none. The statement is that a number which does not stay put is an awkward instrument for a payment, and anybody doing serious work with crypto eventually has to solve that somewhere in their system: either with a time window, or with an instrument that does not move at all.

That second route is what the third lesson of this path is about. Most people who genuinely get paid in crypto are not taking Bitcoin; they take something that claims to be one dollar and to stay there. What that claim rests on, and where it can break, is a discussion of its own.

What does somebody reading this actually do with it?

Settlement across a border, and almost nothing else. The reader this path is written for has delivered the work and their client is on the other side of a border; for them crypto is not an asset, it is a pipe. Money goes in one end and comes out the other, and what they want is for the agreed amount to be what comes out.

We use it for exactly that ourselves and claim nothing more. Wallet top-ups for the SEO tools on this site have a crypto route, because an ordinary card gateway does not reach a customer paying in a foreign currency. That one sentence is the entire technical reason the thing exists on our site. We have written up paying for foreign services before, on the page about buying AI tools, using the same method: only what we have seen ourselves.

And the boundary of this page: we do not say where to buy, which exchange to choose, or how to get past anybody restriction. Nothing of that kind is written in any lesson of this path. The legal status of these activities also differs by country and does not stay put; we are not lawyers, and the rule that applies where you are today has to come from an official source there.

The next step, if this has answered your question so far, is the ledger itself. The next lesson says how a blockchain works and why rewriting its history is hard, and after it comes the stable instrument most real payments are made with. And if crossing a border is the whole problem, one route that removes it entirely is domestic work, which is what our own freelance marketplace was built for.

The fast path, with AI

A message arrives from a client, full of jargon: send USDT, TRC20, or we will pay in USDC on Base. The usual route is to search word by word and half an hour later hold a few scattered definitions. The fast route takes a minute and hands you something better than a definition: the list of things you must confirm before you agree.

  1. Paste the message itself, unchanged, and say who it is from and what job it concerns. Do not summarise; a summary drops exactly the coin and network detail the whole problem is about.
  2. Ask for three things and no more: which coin and which network are named, what goes wrong if those two do not match, and what happens if the sender names one and sends on the other.
  3. Then ask for a fourth list, explicitly: which claims in this message the model cannot verify and I must confirm with the sender. Everybody skips this step and the entire value of the exercise is in it.
  4. A fast, cheap class of model is enough here, because there is no heavy judgment call, you are only unpacking a text. We keep the current pick in <a class="text-link" href="/en/ai/">the RGB AI reference</a>.

Copy-ready recipe

You are a payments specialist. The text below is exactly the message a client sent, unchanged.

{paste the client message here}

The job: {for example web design, translation, SEO}
Where I am: {country}

Give me four things and write nothing else:
1. Which coin and which network this message names. If either is not stated, say which one is missing.
2. What goes wrong if the coin and the network do not match.
3. What happens if the sender names one network and sends on another.
4. The list of claims in this message you cannot verify and I must confirm with the sender.

Do not write any wallet address or contract address, not even as an example.

Before you trust the output: One rule with no exception: an address never comes out of a model, it only ever goes in. The address comes from the other side and you confirm it through a second channel. If the answer contains any wallet or contract address you did not paste in yourself, throw the whole answer away and ask again; that one item tells you the model is inventing.

AI in this kind of work

In this subject the line between what a language model does well and what it is dangerous at is sharper than in any other. It is good at explaining a term and at reading a text you pasted in yourself. It becomes dangerous the moment it produces a string of characters that stands for money.

Tools that actually help

  • Claude It works well on raw text you paste in: a client message, a block explorer page, a service term sheet. Iran is on neither of Anthropic two supported-countries lists, and we read that on Anthropic own page rather than measuring it.
  • Gemini The same job, and smoother at rendering the vocabulary of this field into Persian. Google own page says the Gemini web app runs in over 230 countries and territories, and Iran is not on that list.
  • ChatGPT It serves the same job, but we write nothing about reaching it from Iran that has no source behind it: OpenAI supported-countries page returns a 403 to this server, so its status is unknown to us and stays unknown.

Where it backfires

Two risks, and the first one has no undo. First, a model produces a wallet address or a contract address exactly the way it produces a fluent sentence, and because a crypto transfer is irreversible, an invented address is money gone with nowhere to appeal. So an address is never taken from a model, only ever given to it. Second, never paste a recovery phrase or a private key: Google own privacy page for Gemini states that human reviewers, including trained reviewers from its service providers, read some of the collected data, that chats reviewed by humans are retained for up to three years even if you delete your activity, and it explicitly asks you not to enter confidential information you would not want a reviewer to see. A recovery phrase is the single most confidential string a person owns.

Sources: Anthropic: supported countries Google: where you can use the Gemini web app Google: Gemini Apps privacy notice and data

Where this advice stops

This lesson says what a cryptocurrency is. It does not say whether you should use one, where to get one, or whether doing so is permitted where you are. It says nothing about whether any particular coin is sound. It has one more boundary worth stating plainly: everything here is written for somebody who wants to be paid for work, not for somebody who wants to hold an asset. If your question is the second one, this page is answering a different question.

From our own work

Our own site takes crypto for wallet top-ups, and the thing we learned while building it is written in the code on this server right now: an invoice locks its rate for exactly 90 minutes and then expires. 90 is not a number picked because it looks tidy; it is the longest we are willing to stand behind a price, and beyond that we are carrying the volatility risk for the customer without having been paid to carry it. The effect shows in the same table: all four invoices sitting there today are marked expired, meaning not one of those four people paid inside the 90 minute window and the invoice had to be built again. On a teaching page that is only a setting; for us it is a decision that gets made again every time somebody is late.

Real follow-up questions

Are cryptocurrency, crypto and digital currency the same thing?

Yes, those are three names for one thing and you may use any of them. But coin and token are not the same, and that is the pair that matters in practice: a coin has its own network, a token is a contract on somebody else network. The third section of this lesson shows why confusing the two gets expensive.

If the ledger is public, can everybody see how much I have?

Anybody can see the balance and the whole history of any address, without permission and without an account. What the ledger does not hold is which address belongs to whom; but the moment something links an address to you, every past and future transaction of that address is linked to you as well, and that link does not come undone. The security path opens the same subject from the privacy side.

Why can a mistaken transaction not be reversed?

Because there is nobody in the middle with that authority, and that absence is exactly what allowed the transfer to happen without anybody permission. The only way back is for the recipient to send it back voluntarily. The practical consequence is a habit: confirm the address through a second channel before you send, and when the amount matters, send a small test first.

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