What does online-service do? is one of the earliest online services on the Ukrainian market that offers profitable courses, responsive technical support and an easy-to-use website.

Here you can choose the directions that interest you, since we work with more than 25 cryptocurrencies, as well as with the most popular banks in Ukraine and other payment systems.

Out support team are ready to provide you with full assistance from the moment you go to our site and until the end of the exchange at all times.

How service works?

Work schedule – 24 hours.

How to contact us?

You can write us in online-chat;
Send an e-mail on [email protected]

How to create an application?

To create an application You need to follow the instruction:

1. Choose the direction of the exchange (for example, in the column “You give” – Ethereum, in the column “You receive” – Bitcoin) and fill in the amount You would like to exchange or receive.
2. Fill in your information in the column “Personal information”, such as you e-mail, wallet number (account or card number) where you would like to receive money.
3. Press the button “Exchange” and after that the window with our payment details pops-up.
4. Copy our payment details and go you your wallet. Paste the amount stated in the application and our payment details. Confirm the transfer. Make sure that the amount was withdrawn from your account.
5. Then go back to our website and confirm the payment by pressing the “I paid” button. And it’s done.
6. After creating the application You will receive an e-mail with the status of your application.

How long does the processing of the application take?

The exchange is processed by the operator manually and takes from 5 to 30 minutes after receiving of payment on application, the exchange speed also depends on the workload of our operators.

Why does the processing of my application take so long?

1. The exchange is processed manually by the operator and takes from 5 to 30 minutes. After receiving of payment, the applications are processed in order of priority. The speed of processing an application depends on the workload of our operators. There may also be other reasons:

The first and most common reason is that the application was not created. Remember, if you did not click the “I paid” button, the application is not created and we do not see it in the list of applications awaiting processing. If you accidentally closed or reloaded the page with this button, write to us online support and we will help you with this problem.

2. Check if the amount you sent matches the amount indicated in the application. If the payment amount differs from the amount indicated in the application, the application will get the “Deleted” status. In this case, also contact online support on our website and we will be happy to help You.

3. Incorrect details may also cause a delay in processing your application. Carefully check the specified details when filling in the application. If a mistake is made, we will not be able to transfer funds to you and the application will be on “On review” status. In this case, send us the correct details with the number of your application by email to [email protected] and we will process your application manually as soon as possible.

4. Check if you have copied our payment details correctly. If we wouldn’t receive payment on the application on our account, your application will be moved to the “Deleted” status. Also, there are currently frequent cases of spoofing addresses on the clipboard. In this case, it is necessary to check the computer for viruses and not use it to make payments until the virus is completely removed. If you did not notice the substitution and made a transfer to the wrong details, we, unfortunately, will not be able to help.

I paid for the application, but I didn’t receive money on my account. What is the reason?

There could be different reasons for that. In order for the exchange to be successfully completed, please, make sure, that you did everything correctly:

1. Check if you have correctly entered your transfer details (wallet, account or card numbers). If the details are incorrect, the status of your application will be “On review”, and then you will receive an e-mail with a description of the reason. If the incorrect details were used, a refund is impossible. We recommend that you carefully verify the accuracy of the specified data before creating the application;

2. Check if the amount was charged from your account. If we wouldn’t receive your funds your application would be deleted;

3. There may be a delay in the transfer from the payment systеm or the bank. In this case, we are unable to speed up the process, we can only wait. To find out the reasons for the delay, you can call or write technical support for your payment systеm or your bank;

4. All reasons are individual. Therefore, if your reason does not correspond to any of the above, you can write to us on the online support on our website.

We are always happy to help!

How to track the status of my application?

You can track the status of your application in your account in the “My Applications” section.
This information is also available by mail, which you entered when you created the application (registration). You will automatically receive messages with information about the change in the status of your application.

Is it possible to cancel my application?

In case your application was processed, your funds cannot be refunded.
If your application was paid, but not processed, you can get a refund (excluding the service fees), by writing to our online support on our website.

I didn’t receive an e-mail with my password/account activation

If you did not receive a letter confirming the email address within 24 hours from the moment of your registration, then, first of all, you need to make sure that you entered the correct email during the registration. In addition, some mail services may move such messages to spam folder or not deliver them at all. The following points can help you solve the problem:
1. Make sure that you entered the correct email at registration. Go through the registration procedure again in order to do that. If a message appears that the email address was already used, then it was entered correctly;
2. Make sure that you check the mailbox that you entered during registration. This is especially relevant for those who use several e-mails, or several family members use the computer;
3. Check the “Spam” folder;
4. Check your spam filter settings (if you use them);
5. Contact the technical support of your email service and find out, were there any limitations from their side.
If none of the points haven’t helped, contact the online support on our website.

I forgot the password to my account. How can I restore it?

Go to the password recovery page (“Forgot password” button) and enter the registered e-mail (login). An email will be sent to your mailbox with a link to confirm the password recovery. You have to open the letter and go to the page. After confirming the change of the password, you can fill in a new password.

What are your fees?

The fees of our service are already included in the exchange rate and are displayed at the stage of application processing, including the transfer fees of the payment systеm.

What is referral program and how can you earn on it?

We created a simple and beneficial partnership program. This program provides you the opportunity to receive bonuses from us if your friends use our services.
You can receive additional bonus from us in amount of 0,05-0,025% from the amount exchanged by the person, who used your referral link. In the future you will receive bonuses from all the exchanges of your referral.

The amount of the bonuses:

  • 500-4999 USD — 0,05% of the exchanged amount
  • 5000-9999 USD — 0,1% of the exchanged amount
  • 10000-24999 USD — 0,15% of the exchanged amount
  • 25000-49999 USD — 0,2% of the exchanged amount
  • more than 50 000 USD — 0,25% of the exchanged amount

Our partnership program has 5 levels. Partner moves to the next level of the program automatically after your referrals exchange the certain amounts.
Everyone can earn with our partnership program. You just need to register on our website and use the special partnership link, that You can find in your profile in the section Partnership program.
It is welcome to use our advertising materials You can also find in your profile in Partnership program section.
Referral bonuses are allocated in Perfect Money USD, Advanced Cash currency right after the processing of the exchange application. You can submit a withdrawal application immediately after the referral money is allocated.
Minimum amount of withdrawal is 10 USD.

What is card verification process and why it has to be done?

This is a procedure of the user data confirmation, which increases the security of transactions and personal data within the exchange service. During verification, you need to upload photos and scanned copies of your documents. After the verification procedure of the account, sales/purchase of cryptocurrency using Visa/MasterCard bank cards are available for the user.

I was asked to clear Cookies and Cache. How can I do it?

The web pages of our site may not be displayed correctly due to the fact that changes have been made there, and your browser continues to use outdated data from the cache.
In such cases, we ask you to clean the Cookies and Cache in order for all the functionality to fully and accurately work.
You can find the instructions for clearing cookies and cache in your browser.

BTC transaction stuck: main ways to solve the problem

Once a transaction is broadcast on the Bitcoin network, it can be included in a block that is published on the network. To protect yourself against double spending, a transaction should not be considered confirmed until it reaches a certain number of blocks.

Please note that unconfirmed transactions will not be canceled.

A classic bitcoin client will show the transaction as “n / unconfirmed” until the transaction reaches a depth of 6 blocks.

Why is the transaction stuck?

The most common reason for freezing is transactions with too low fees. If there are any transactions with higher fees on the network, then miners have no incentive to confirm those that pay them little. This is why transactions with low fees must wait longer.

The second most common reason for the “Not Confirmed” status is the presence of previously unconfirmed transfers. Usually transactions need to be confirmed in order. New transactions usually cannot be confirmed as long as there are others on the Bitcoin or Ethereum network that are higher in Mempool.

What to do to ensure that transactions do not remain unconfirmed

It is best to set the commission correctly at the time of sending. Many cryptocurrency wallets allow you to choose how much to pay for the miner’s commission. For coins that provide you with 3 commission options (low, normal, high), we recommend choosing “high” commission priority for faster confirmation.

Mobile wallets often cannot predict future network load, so they may not be suitable in the event of a very sudden increase in network activity.

If the commission was set too low when sending, then your deal gets the “Pending” status.

How to speed up the confirmation of an unconfirmed transaction?

Incoming transaction

If you receive an unconfirmed transaction, your only option is to wait. The sender is responsible for the correct setting of the commission. You can contact the sender to ask them to use a higher commission next time.


If you sent an unconfirmed Ethereum or ERC-20 token transaction, you can rеplace that transaction with another one with higher fees. You can find step-by-step instructions here. However, making new transactions with Ethereum or tokens without following the instructions will NOT result in faster confirmation of previous transactions.


If you submitted an unconfirmed Bitcoin transaction, there are a number of services that claim to speed up confirmations, such as and The effectiveness of these services is not guaranteed. There is no way to find a completely reliable service that will best speed up a transaction.

You can also check if there is an outgoing transaction in the blockchain explorer. If the transaction has 2 destinations, you can follow these steps to speed it up. This method is called Child Pays for Parent (CPFP).

How to speed up unspent BTC transactions?

  • Copy your own bitcoin receiving address
  • Paste the copied address into the send box
  • Use the max button to send all funds
  • Go to the confirmation screen and sеlect the HIGH priority board or the high commission value.
  • Send and wait for transaction confirmation

There are other options for acceleration, such as “RBF”, which stands for rеplace By Fee (rеplace with another commission).

An RBF transaction is a method that allows the sender to rеplace a stuck or unconfirmed transaction with a new one with a higher fee. This is done to ensure that the transaction is confirmed faster. The “rеplace” transaction uses the same input as the original. This is not considered a double charge as the receiving address remains the same.

Error: Not Enough ETH to Send

If you are getting the error that looks like this: “Not enough ETH to send”, it means you do not have enough ETH in your account to cover the cost of gas.

Each transaction (including token and contract transactions) requires gas, and that gas is paid in ETH. You can think of this like a transaction fee.

Solution: Send 0.01 ETH to that account in order to be able to make the transaction.

More Information About Gas

A standard TX will be 21000 gas & a gas price of 0.00000002 ETH so the total TX fee will be 0.00042 ETH.

With tokens, the amount of gas is typically 50000 gas – 100000 gas, so the total TX fee increases to 0.001 ETH – 0.002 ETH.

The amount of ETH or tokens you are sending does not affect the amount of gas you need.

Gas limit is the maximum amount of gas you will send with your transaction. This is in units of gas.

Gas price is how much each unit of gas costs. It can be adjusted via the Settings page, or by adjusting the ‘Transaction Fee’ on the ‘send transaction’ page.

What is the confirmation of the Bitcoin & Altcoins network and how long does it take ?

Confirmation of the transaction is necessary in order to prevent repeated expenditure of the same funds.

Once the sender transfers funds, the transaction enters the Bitcoin/Altcoins network for execution and inclusion in the block.

It is the process of adding a transaction to the structure of the found block, called the transaction confirmation, one block includes one confirmation.

Once your transaction is confirmed, Bitcoin/Altcoins coins become available for future use.

The speed of confirmation depends on a number of factors, such as: the workload of the Bitcoin/Altcoins network itself, the amount of commission specified during the transfer, the speed of the Internet connection, the technical serviceability of the resource where your wallet is located, etc.

As you probably know, before a transaction gets to the miners, the nodes relay it to each other until it spreads across the network. Transactions that have not yet been processed and confirmed by the miners are stored in the memory of the nodes in the pool (mempool). While the transaction is stored in the pool (mempool) it is not visible on the Blockchain Explorer (,

Sometimes a transaction can be stored in a pool (mempool) 6–48 hours.

On average, the transaction confirmation lasts from 30 minutes to several hours.

But sometimes confirmation can wait 2-14 days if the Bitcoin/Altcoins network is overloaded.

We, when sending Bitcoin, pay the recommended commission according to the recommendations of the site

We can not affect the time and speed of transaction confirmation on the Bitcoin/Altcoins network.

Is there a confirmation on the Bitcoin/Altcoins network?

Confirmation of operations in the Bitcoin/Altcoins network depends on the work of the miners. It is these people who make the work of the Bitcoin/Altcoins network live and act solely for their financial interests. The exchanger does not deal with the mining of Bitcoin/Altcoins coins and can not in any way affect the work of the miners. This is a process that does not depend on us, which occurs after the transfer of Bitcoin/Altcoins coins from the exchanger’s address to the address specified by the user in the application.

You will wait for confirmation by the network until the miner does not perform certain actions to extract the blocks. These are the fundamental properties of the Bitcoin/Altcoins network. If you intend to continue using Bitcoin/Altcoins coins, you will have to face it.

The exchanger’s obligations are considered fulfilled after the transfer of Bitcoin/Altcoins coins to the address specified by the client, which is confirmed by a record in the public registry. In our work we do not promise any increased commissions for the transaction, but we pay the standard commissions recommended by the network at the time of transfer. We do not predict the time of confirmation in the Bitcoin/Altcoins network and do not give any recommendations on this matter.

Any claims to the exchanger in relation to acknowledgments in the Bitcoin/Altcoins network are groundless and meaningless, Confirmation in the Bitcoin/Altcoins network is an uncontrolled process, a process that depends on the actions of third parties. This process occurs after the successful completion of the exchange in the user’s wallet.

Bitcoin/Altcoins has been downloaded frequently. This can be caused by various circumstances: a large number of unprocessed transactions, all kinds of attacks on the network by hackers, etc. The result is one. In such periods, the waiting time for confirmations can increase from several hours to several days.

Bitcoin/Altcoins payments can not be canceled.

No Bitcoin/Altcoins transaction can be canceled. Only if the recipient himself returns the funds, you can get them back.

You pay/receive an amount in Bitcoin/Altcoins, but not in dollars/rubles or hryvnia.

At the exchange you agree with everything written above.


Hash ID Transactions – what it is and how to find the TXID transaction.


Cryptographically protected transaction identifier in the distribution register of blockchain, which is assigned to each cryptocurrency operation after its formation.

ID of the transaction (TXID)

is a 64-character code consisting of a certain sequence of letters and numbers. This code is generated individually for each transaction and contains information about it, but at the same time is publicly available. Its transmission to third parties is absolutely safe, because all personal information is encrypted, without the possibility of restoring the original data.

The confirmation of the sent payment can only be a txid (bitcoin identifier) of the payment.

How do I know TXID?

Most cryptocurrencies operate on open blockchain registries, where information is publicly available to all users. But despite the importance of the identifier and the openness of blockchain, not every average user knows where to look at TXID and how to track the transaction.

TXID can be viewed in the operations log of the cryptocurrency wallet from which the transaction was made. Special services have also been developed that allow you to get the identifier of the transaction knowing its other data. For example, TXID check for different cryptocurrencies is available through services:

To find out TxID or TxHash, find your BTC address or the address of the recipient in block explorer. If you see a lot of transactions in the list, just find the amount of Bitcoins you sent.

This way you can find this particular transaction. Once you have found your transaction, you should also find the transaction’s hash identifier. You can simply share the transaction identifier or find it and share the URL of the page with the recipient.


What are Memo/Destination Tag/Message and why and when we need them?

A distinctive feature of Stellar/Ripple/Xem transfers between wallets is the additional verification of the transfer by indicating Memo/Destination Tag/Message. This is an additional field in the wallet or on the exchange, which must be filled in order not to lose the transfer.
They are unique and with their help, the exchange indicates who transferred the funds and on whose account they must be allocated.
Without specifying a Payment ID, you can lose coins during the transfer forever. About whether a Payment ID is needed or not, you will be informed in the payment instructions.

What is Fiat Currency?

Simply put, fiat currency is legal tender that derives its value from its issuing government rather than a physical good or commodity. The strength of the government that establishes the value of fiat currency is key in this type of money. Most countries around the world use the fiat currency systеm to purchase goods and services, invest, and save. Fiat currency replaced the gold standard and other commodity-based systems in establishing the value of legal tender.

The Rise of Fiat Currency

Fiat currency originated centuries ago in China. The Szechuan province began issuing paper money during the 11th century. At first, it could be exchanged for silk, gold, or silver. But eventually, Kublai Khan came into power and established a fiat currency systеm during the 13th century. Historians claim this money was instrumental in the downfall of the Mongol Empire, with excessive spending and hyperinflation at the root of its decline.

Fiat money was also used in Europe during the 17th century, being adopted by Spain, Sweden, and the Netherlands. The systеm was a failure in Sweden and the government eventually abandoned it for the silver standard. Over the next two centuries, New France in Canada, the American Colonies, and then the U.S. Federal Government also experimented with fiat money with mixed results.

By the 20th century, the U.S. was back to using commodity-based currency on a somewhat limited basis. In 1933, the government ended the practice of exchanging paper money for gold. By 1972, under President Nixon, the U.S. abandoned the gold standard altogether, finalizing its demise on an international scale, switching to the fiat currency systеm. This led to the use of fiat currency around the globe.

Fiat Currency vs. The Gold Standard

The gold standard systеm permitted the conversion of paper bills to gold. In fact, all paper money was backed by a finite amount of gold that was held by the government. Under a commodity-based currency systеm, governments and banks could only introduce new currency into the economy if they held an equal amount in value of gold stores. This systеm limited the government’s ability to create money and to increase the value of their currency based solely on economic factors.

On the other hand, under the fiat currency systеm, money may not be converted to anything else. With fiat money, authorities can directly impact the value of their currency and tie it to economic conditions. Governments and their countries’ central banks have far more control of currency systems. They can respond to varying financial events and crises with different tools, like the creation of fractional reserve banking and the implementation of quantitative easing.

Advocates of the gold standard argue that a commodity-based currency systеm is more stable because it’s backed by something that is physical and valuable. Fiat currency supporters counter that gold prices have been anything but stable. In this context, the value or worth of both commodity-based currency and fiat money can fluctuate. But with a fiat currency systеm, the government has more flexibility to act when there’s an economic emergency.

Some Pros and Cons of Using Fiat Currency

Economists and other financial experts are not unanimous in their support of fiat currency. Defenders and opposers passionately argue the pros and cons of this currency systеm.

  • Scarcity: Fiat money is not impacted and limited by the scarcity of a physical commodity like gold.
  • Cost: Fiat money is more affordable to produce than commodity-based money.
  • Responsiveness: Fiat currency gives governments and their central banks the flexibility to address economic crises.
  • International Trade: Fiat currency is used in nations around the world, making it an acceptable form of currency for international trade.
  • Convenience: Unlike gold, fiat money is not reliant on physical reserves that require storage, protection, monitoring, and other costly demands.
  • No Intrinsic Value: Fiat currency holds no intrinsic value. This allows governments to create money from nothing, which could lead to hyperinflation and collapse their economic systеm.
  • Historically risky: Historically, the implementation of fiat currency systems has typically led to financial collapses, which indicates that these systems present some risks.

Fiat Currency vs. Cryptocurrency

Fiat currency and cryptocurrency have a bit of common ground in that neither of them is backed by a physical commodity – but that’s where the similarity ends. While fiat money is controlled by governments and central banks, cryptocurrencies are essentially decentralized, largely due to a distributed digital ledger called Blockchain.

Another notable difference between these two currency systems is how each of these forms of money is generated. Bitcoin, like most cryptocurrencies, has a controlled and limited supply. In contrast, banks can create fiat money out of nothing, according to their judgment of a nation’s economic needs.

As a digital form of money, cryptocurrencies have no physical counterpart and are borderless, making them less restrictive for worldwide transactions. Moreover, the transactions are irreversible, and the nature of cryptocurrencies makes tracking considerably more difficult when compared to the fiat systеm.

Noteworthy, the cryptocurrency market is much smaller and, thus, way more volatile than traditional markets. This is probably one of the reasons cryptocurrencies are not yet universally accepted, but as the crypto economy grows and matures, volatility will likely decrease.

Closing thoughts

The future of both these forms of currency is in no way certain. While cryptocurrencies still have a long way to go and will certainly face many more challenges, the history of fiat currency demonstrates the vulnerability of this form of money. That’s a big reason many people are exploring the possibilities of moving towards a cryptocurrency systеm for their financial transactions – at least in some percentage.

One of the main ideas behind the creation of Bitcoin and cryptocurrencies is to explore a new form of money that is built on a distributed peer-to-peer network. Chances are Bitcoin was not created to rеplace the whole fiat currency systеm, but to offer an alternative economic network. Still, it certainly has the potential to create a better financial systеm for a better society.

What Are Smart Contracts?


Nick Szabo first described smart contracts in the 1990s. Back then, he defined a smart contract as a tool that formalizes and secures computer networks by combining protocols with user interfaces.

Szabo discussed the potential use of smart contracts in various fields that involve contractual agreements – such as credit systems, payment processing, and content rights management.

In the world of cryptocurrencies, we may define a smart contract as an application or program that runs on a blockchain. Typically, they work as a digital agreement that is enforced by a specific set of rules. These rules are predefined by computer code, which is replicated and executed by all network nodes.

Blockchain smart contracts allow for the creation of trustless protocols. This means that two parties can make commitments via blockchain, without having to know or trust each other. They can be sure that if the conditions aren’t fulfilled, the contract won’t be executed. Other than that, the use of smart contracts can remove the need for intermediaries, reducing operational costs significantly.

Although the Bitcoin protocol has been supporting smart contracts for many years, they were made popular by the creator and co-founder of Ethereum, Vitalik Buterin. It’s worth noting, though, that each blockchain may present a different method of implementing smart contracts.

This article will focus on the smart contracts that run on the Ethereum Virtual Machine (EVM), which is an essential part of the Ethereum blockchain.

How do they work?

In simple terms, a smart contract works as a deterministic program. It executes a particular task when and if certain conditions are met. As such, a smart contract systеm often follows “if… then…” statements. But despite the popular terminology, smart contracts are not legal contracts, nor smart. They are just a piece of code running on a distributed systеm (blockchain).

On the Ethereum network, smart contracts are responsible for executing and managing the blockchain operations that take place when users (addresses) interact with each other. Any address that is not a smart contract is called an externally owned account (EOA). Thus, smart contracts are controlled by computer code, and EOAs are controlled by users.

Basically, Ethereum smart contracts are made of a contract code and two public keys. The first public key is the one provided by the creator of the contract. The other key represents the contract itself, acting as a digital identifier that is unique to each smart contract.

The deployment of any smart contract is made through a blockchain transaction, and they can only be activated when called by an EOA (or by other smart contracts). However, the first trigger is always caused by an EOA (user).

Key features

An Ethereum smart contract often presents the following characteristics:

  • Distributed. Smart contracts are replicated and distributed in all nodes of the Ethereum network. This is one of the major differences from other solutions that are based on centralized servers.
  • Deterministic. Smart contracts only perform the actions they were designed to, given the requirements are met. Also, the outcome will always be the same, no matter who executes them.
  • Autonomous. Smart contracts can automate all sorts of tasks, working like a self-executing program. In most cases, though, if a smart contract isn’t triggered, it will stay “dormant” and won’t perform any action.
  • Immutable. Smart contracts can’t be changed after deployed. They can only be “deleted” if a particular function was previously implemented. Thus, we may say that smart contracts can provide tamper-proof code.
  • Customizable. Before deployment, smart contracts can be coded in many different ways. So, they can be used to create many types of decentralized applications (DApps). This is related to the fact that Ethereum is a Turing complete blockchain.
  • Trustless. Two or more parties can interact via smart contracts without knowing or trusting each other. In addition, blockchain technology ensures that data is accurate.
  • Transparent. Since smart contracts are based on a public blockchain, their source code is not only immutable but also visible to anyone.

Can I change or dеlete a smart contract?

It’s impossible to add new functions to an Ethereum smart contract after deployed. However, if its creator includes a function called SELFDESTRUCT in the code, they are able to “dеlete” the smart contract in the future – and rеplace it with a new one. In contrast, though, if the function isn’t included in the code beforehand, they won’t be able to dеlete it.

Notably, the so-called upgradeable smart contracts allow developers to have more flexibility over contracts’ immutability. There are many ways to create upgradeable smart contracts, with varying degrees of complexity.

Taking a simplified example, let’s imagine that a smart contract is divided into multiple smaller contracts. Some of them are designed to be immutable, while others have the ‘dеlete’ function enabled. This means that part of the code (smart contracts) can be deleted and replaced, while other functionalities remain intact.

Advantages and use cases

As programmable code, smart contracts are highly customizable and can be designed in many different ways, offering many kinds of services and solutions.

As decentralized and self-executing programs, smart contracts may provide increased transparency and reduced operational costs. Depending on the implementation, they can also increase efficiency and reduce bureaucratic expenses.

Smart contracts are particularly useful in situations that involve the transfer or exchange of funds between two or more parties.

In other words, smart contracts can be designed for a wide variety of use cases. Some examples inсlude the creation of tokenized assets, voting systems, crypto wallets, decentralized exchanges, games, and mobile applications. They may also be deployed along with other blockchain solutions that are tackling the fields of healthcare, charity, supply chain, governance, and decentralized finance (DeFi).


Tokens issued on the Ethereum blockchain follow a standard known as ERC-20. The standard describes the core functions of all Ethereum-based tokens. As such, these digital assets are often referred to as ERC-20 tokens, and they represent a great portion of the existing cryptocurrencies.

Many blockchain companies and startups deployed smart contracts in order to issue their digital tokens on the Ethereum network. After the issuance, the majority of these companies distributed their ERC-20 tokens through Initial Coin Offering (ICO) events. In most cases, the use of smart contracts enabled the exchange of funds, and distribution of tokens, in a trustless and efficient way.


Smart contracts are made of computer code written by humans. This brings numerous risks as the code is subject to vulnerabilities and bugs. Ideally, they should be written and deployed by experienced programmers, especially when involving sensitive information or large amounts of money.

Other than that, some argue that centralized systems can provide most of the solutions and functionalities offered by smart contracts. The main difference is that smart contracts are running on a distributed P2P network, rather than a centralized server. And because they are based on a blockchain systеm, they tend to be either immutable or very hard to change.

Being immutable can be great in some situations, but very bad in others. For example, when a Decentralized Autonomous Organization (DAO) called “The DAO” got hacked in 2016, millions of ether (ETH) were stolen due to flaws in their smart contract code.

Since their smart contract was immutable, developers were unable to fix the code. This eventually led to a hard fork, giving birth to a second Ethereum chain. Simply put, one chain “reverted” the hack and returned the funds to the rightful owners (this is part of the current Ethereum blockchain). The other chain decided to not interfere with the hack, stating that things that happen on a blockchain should never be changed (this chain is now called Ethereum Classic).

It’s important to note that the problem didn’t come from the Ethereum blockchain. Instead, it was caused by a faulty smart contract implementation.

Another limitation of smart contracts is related to their uncertain legal status. Not only because it’s in a grey area in most countries, but also because smart contracts don’t suit the current legal framework.

For example, many contracts require both parties to be properly identified and over 18 years old. The pseudonymity provided by blockchain technology, combined with the lack of intermediaries, may threaten those requirements. While there are potential solutions to this, the legal enforceability of smart contracts is a real challenge – especially when it comes to borderless, distributed networks.


Some blockchain enthusiasts see smart contracts as a solution that will soon rеplace and automate a great part of our commercial, and bureaucratic systems. While this is a possible reality, it’s probably far from becoming the norm.

Smart contracts are certainly an interesting piece of technology. But, being distributed, deterministic, transparent, and somewhat immutable can make them less appealing in some situations.

Essentially, criticism relies on the fact that smart contracts are not a suitable solution for many real-world problems. In fact, some organizations are better off using conventional server-based alternatives.

When compared to smart contracts, centralized servers are easier and cheaper to maintain, and tend to present a higher efficiency in terms of speed and cross-network communication (interoperability).

Closing thoughts

There is no doubt that smart contracts caused a big impact in the world of cryptocurrencies, and they certainly revolutionized the blockchain space. While the end-users may not interact directly with smart contracts, these are likely to power a wide range of applications in the future, ranging from financial services to supply chain management.

Together, smart contracts and blockchain have the potential to disrupt almost all areas of our society. But only time will tell if these groundbreaking technologies will manage to overcome the many barriers to large-scale adoption.


Tether is the most popular stablecoin today (and ranked in the top 7 cryptocurrencies by market cap according to CoinMarketCap). We have tried for you to understand the secrets of the success of this cryptocurrency and its features.

What is Tether?

Tether is a pioneer in the stablecoin world. It makes it possible to store cryptocurrencies pegged 1: 1 to the dollar (USDT), euro (EURT) and Chinese yuan (CNHT). Coins are issued by Tethet Limited, the reserves of which underpin all issued tokens. Each of the coins issued is backed by a corresponding fiat currency. This allows Tether stablecoins to be less prone to volatility compared to traditional cryptocurrencies.

Omni Protocol

Since 2014, the release of stablecoins has been based on the Omni Layer protocol (after rebranding in 2016, it shortened its name to Omni). It is an open protocol that is built on top of the Bitcoin blockchain. The Omni platform allows you to create digital assets, smart contracts, and decentralized Peer-to-peer exchanges.

Using the Bitcoin network gives the Omni protocol a number of advantages, including the security and stability of the BTC network itself. All coins that are created in Omni over the network are tokens on the Bitcoin blockchain. All exchanges and wallets compatible with BTC are automatically compatible with Omni tokens.

Among the disadvantages of the protocol, like the Bitcoin blockchain, are the low speed of transactions on the network (on average, one transaction is about 10 minutes), as well as high fees and block restrictions.

Tether and Ethereum

In February 2018, the release of Tether tokens was carried out on the Ethereum blockchain according to the ERC20 standard. This transition allowed Tether to be used in smart contracts and decentralized apps powered by Ethereum. In addition, the average time on the Ethereum network is only 15 seconds, instead of 10 minutes on the BTC network. The undoubted advantage of the Ethereum network is the lower transaction fees.

Since Tether uses different protocols, users need to verify addresses when sending funds. Tokens of one standard cannot be transported to another network.

Tether and Tron

In April 2019, the company began issuing USDT based on the Tron blockchain. Stablecoins are launched based on TRC-20, the technical standard used by the Tron blockchain to sell tokens, similar and compatible with the Ethereum ERC-20 standard. The addition of a coin on the Tron blockchain was conceived to develop the Tron decentralized application (dApps) ecosystem.

On our website, you can both buy and sell Tether of any of the 3 presented protocols.

Cryptocurrency security – basic rules

Basic rules

These are the most basic safety rules that everyone needs to know. Compliance with them will allow you to protect yourself in 99% of cases.

  • Use complex passwords. This is a common truth, but many people forget about it.
  • Do not store passwords electronically; it is better to write them down on a piece of paper.
  • For registrations on cryptocurrency exchanges and other transactions, use a separate email and phone. They should never be shown to anyone. Key services should be tied to the mail that no one knows.
  • Maintain confidentiality, do not publish any data about yourself. Do not brag about the presence of cryptocurrency (and money in general) Cryptocurrency rates sometimes change dramatically, and your currency can become a tidbit for intruders.
  • Follow all the recommended safety guidelines for any service (be it a cryptocurrency exchange or email).
  • Do not register on suspicious sites, do not download dubious applications to your phone, do not install extensions and plugins from unknown developers on the browser.
  • Always remain vigilant and attentive. Before you press any button on a new site, carefully study it, it may be a phishing project that collects data.
  • Download all applications only from the official websites of the developers. If they are paid, then you do not need to try to save a couple of hundreds dollars by looking for free ones. They can contain malware, which is very common in the cryptocurrency sphere.
  • Follow all the basic security rules that everyone should know (using antivirus software, files only from reliable sources, etc.).

Security on cryptocurrency exchanges

All exchanges have different registration requirements, different rules, but today their security is at a high level (if we talk about top platforms). However, they do not have “foolproof”, so if you neglect their recommendations, then the risk will always be. Some exchanges are forcibly forced to enable two-factor authentication, which, although not very convenient, significantly increases the security of the account. We recommend that you follow all the security best practices for each specific cryptocurrency exchange and use all security tools. Losing even a couple of minutes a day is incomparable with losing all your money.

In addition, when registering, you must indicate real data about yourself. In case of any problems and fictitious data, it will be very difficult for you to prove your case. A trivial example: the exchange suspected that your account was hacked and blocked it. And if you indicated fictitious data during registration, then it will be incredibly difficult to return your account. By the way, this also applies to email and other mission-critical services.

Storing cryptocurrency in a wallet

Download wallets only from the official websites of the developers, otherwise there will be a possibility that there is a built-in “surprise” that will become very unpleasant for you. Set the maximum security level. Do not download smartphone apps unnecessarily, they are themselves susceptible to hacks and attacks, so this is an additional risk.

For long-term storage of cryptocurrency, it is safest to use cold wallets or hardware wallets. From a security point of view, there is no difference between them, but the former are free or cheap (the price of a flash drive), unlike the latter. Many cryptocurrencies TRON, Monero, Lisk, etc., allow you to print paper wallets, which is not very convenient, but 100% safe. Ideal for long-term storage of cryptocurrency.

Popular ways to steal cryptocurrency

This is not a complete list, just a few examples that allow you to understand exactly how cryptocurrency theft occurs.

Creation of fake cryptocurrency exchange websites. With their help, attackers get your username and password. Ideally, they need to know your email, which, under the guise of an official letter, will be sent a link to the site. There are other ways, but they are more time consuming. But this will not work if you use two-factor authentication (hacking is possible here, but you will need to intercept your phone number or access your mail, which complicates the task). However, this is one of the most popular options for losing your cryptocurrency.

Fake wallets that are stitched with a code that allows you to take over control of your cryptocurrency. You download such a wallet, install it, after which the attacker simply transfers your assets to himself.

Banal fraud. They promise to sell cryptocurrency (or buy) at an extremely favorable rate, the expectation of huge profits obscures a person’s eyes, and he transfers money to a fraudster without hesitation. There is no and cannot be protection, and therefore this method will always be in the top in popularity.

Fake exchange offices. And this occurs, although not so often. If you use an exchanger, then at least look for reviews about it. And if his conditions are too attractive, then this will definitely be a reason to be seriously wary.

Any services, ICOs and other sites that promise guaranteed and large profits. Your greed is the main tool for scammers.

Crypto Wallet Types Explained

What is a crypto wallet?

In short, a crypto wallet is a tool that you can use to interact with a blockchain network. There are various crypto wallet types which can be divided into three groups: software, hardware, and paper wallets. Depending on their working mechanisms, they may also be referred to as hot or cold wallets.

The majority of crypto wallet providers are based on software, which makes their use more convenient than hardware wallets. However, hardware wallets tend to be the most secure alternative. Paper wallets, on the other hand, consist of a “wallet” printed out on a piece of paper, but their use is now deemed as obsolete and unreliable.

How do cryptocurrency wallets work?

Contrary to popular belief, crypto wallets don’t truly store cryptocurrencies. Instead, they provide the tools required to interact with a blockchain. In other terms, these wallets can generate the necessary information to send and receive cryptocurrency via blockchain transactions. Among other things, such information consists of one or more pairs of public and private keys.

The wallet also includes an address, which is an alphanumeric identifier that is generated based on the public and private keys. Such an address is, in essence, a specific “location” on the blockchain to which coins can be sent to. This means you can share your address with others to receive funds, but you should never disclose your private key to anyone.

The private key gives access to your cryptocurrencies, regardless of which wallet you use. So even if your computer or smartphone gets compromised, you can still access your funds on another device – as long as you have the corresponding private key (or seed phrase). Note that the coins never truly leave the blockchain, they are just transferred from one address to another.

Hot vs. cold wallets

As mentioned, cryptocurrency wallets may also be defined as “hot” or “cold,” according to the way they operate.

A hot wallet is any wallet that is connected somehow to the Internet.

Cold wallets, on the other hand, have no connection to the Internet. Instead, they use a physical medium to store the keys offline, making them resistant to online hacking attempts. As such, cold wallets tend to be a much safer alternative of “storing” your coins. This method is also known as cold storage and is particularly suitable for long-term investors or “HODLers.”

Software wallets

Software wallets come in many different types, each with its own unique characteristics. Most of them are somehow connected to the Internet (hot wallets). The following are descriptions of some of the most common and important types: web, desktop, and mobile wallets.

Web wallets

You can use web wallets to access blockchains through a browser interface without having to download or install anything. This includes both exchange wallets and other browser-based wallet providers.

In most cases, you can create a new wallet and set a personal password to access it. However, some service providers hold and manage the private keys on your behalf. Although this may be more convenient for inexperienced users, it’s a dangerous practice. If you don’t hold your private keys, you’re trusting your money to someone else. To address this problem, many web wallets now allow you to manage their keys, either entirely or through shared control (via multi-signatures). So it’s important to check the technical approach of each wallet before choosing the most suitable for you.

When using cryptocurrency exchanges, you should consider making use of the protection tools available.

Desktop wallets

As the name implies, a desktop wallet is a software you download and execute locally on your computer. Unlike some web-based versions, desktop wallets give you full control over your keys and funds. When you generate a new desktop wallet, a file called “wallet.dat” will be stored locally on your computer. This file contains the private key information used to access your cryptocurrency addresses so you should encrypt it with a personal password.

If you encrypt your desktop wallet, you will be required to provide your password every time you run the software so that it can read the wallet.dat file. If you lose this file or forget your password, you will most likely lose access to your funds.

Therefore, it’s crucial to backup your wallet.dat file and keep it somewhere safe. Alternatively, you can export the corresponding private key or seed phrase. By doing so, you will be able to access your funds on other devices, in case your computer stops working or becomes inaccessible somehow.

In general, desktop wallets may be considered safer than most web versions, but it’s crucial to make sure your computer is clean of viruses and malware before setting up and using a cryptocurrency wallet.

Mobile wallets

Mobile wallets function much like their desktop counterparts but designed specifically as smartphone applications. These are quite convenient as they allow you to send and receive cryptocurrencies through the use of QR codes.

As such, mobile wallets are particularly suitable for performing daily transactions and payments, making them a viable option for spending Bitcoin, BNB, and other cryptocurrencies in the real world. Trust Wallet is a prominent example of a mobile crypto wallet.

Just as computers, however, mobile devices are vulnerable to malicious apps and malware infection. So it’s recommended that you encrypt your mobile wallet with a password, and backup your private keys (or seed phrase) in case your smartphone gets lost or broken.

Hardware wallets

Hardware wallets are physical, electronic devices that use a random number generator (RNG) to generate public and private keys. The keys are then stored in the device itself, which isn’t connected to the Internet. As such, hardware storage constitutes a type of cold wallet and is deemed as one of the most secure alternatives.

While these wallets offer higher levels of security against online attacks, they may present risks if the firmware implementation is not done properly. Also, hardware wallets tend to be less user-friendly, and the funds are more difficult to access when compared to hot wallets.

You should consider using a hardware wallet if you plan to hold your crypto for a long time or if you’re holding large amounts of cryptocurrency. Currently, most hardware wallets allow you to set up a PIN code to protect your device, as well as a recovery phrase – which can be used in case your wallet is lost.

Paper wallets

A paper wallet is a piece of paper on which a crypto address and its private key are physically printed out in the form of QR codes. These codes can then be scanned to execute cryptocurrency transactions.

Some paper wallet websites allow you to download their code to generate new addresses and keys while being offline. As such, these wallets are highly resistant to online hacking attacks and may be considered an alternative to cold storage.

Owing to the numerous flaws, however, the use of paper wallets is now considered dangerous and should be discouraged. If you still want to use it, it’s essential to understand the risks. A major flaw of paper wallets is that they aren’t suitable for sending funds partially, but only its entire balance at once.

For example, imagine that you generated a paper wallet and sent multiple transactions to fund it, summing a total of 10 BTC. If you decide to spend 2 BTC, you should first send all 10 coins to another type of wallet (e.g., desktop wallet), and only then spend part of the funds (2 BTC). You can later return the 8 BTC to a new paper wallet, though a hardware or software wallet would be a better choice.

Technically, if you import your paper wallet private key into a desktop wallet and spend just part of the funds, the remaining coins will be sent to a “change address” that is automatically generated by the Bitcoin protocol. If you don’t manually set the change address to one that you control, you will likely lose your funds.

Most software wallets today will handle the change for you, sending the remaining coins to an address that is part of your wallet. But the important thing to remember is that your paper wallet will be empty after sending its first transaction out – regardless of the amount. So don’t expect to reuse it later.

The importance of backups

Losing access to your cryptocurrency wallets can be quite costly. So it’s important to back up them regularly. In many cases, this is achieved by simply backing up wallet.dat files or seed phrases. Essentially, a seed phrase works like a root key that generates and gives access to all keys and addresses in a crypto wallet. Also, if you opted for password encryption, remember to back up your password as well.

Closing thoughts

Crypto wallets are an integral part of using Bitcoin and other cryptocurrencies. They are one of the basic pieces of infrastructure that make it possible to send and receive funds through blockchain networks. Each wallet type has its advantages and disadvantages, so it’s crucial to understand how they work before moving your funds.