Cryptocurrencies have given people unprecedented financial freedom and control over their money. However, over time, this advantage has lost its unconditional validity - particularly due to the increasing practice of "freezing" assets.

Typically, "freezing" crypto assets refers to a temporary restriction on a user's ability to manage their savings. Formally, the user remains the owner of the cryptocurrencies, but cannot transact with them until the freeze is lifted. Unlike seizure or repossession, freezing does not imply the permanent loss of funds and can, at least in theory, be reversed.

Blockchain technology itself does not provide a single and universal freezing mechanism. In contrast, decentralized blockchains were originally designed as systems resistant to censorship and restrictions on freedom of disposal of coins. As a general rule, if a user independently controls the private key to his wallet, no external party can prevent him from initiating transactions, receiving or spending his savings.

Therefore, such a freeze occurs not at the base level of the blockchain, but at the level of the infrastructure surrounding cryptocurrencies: exchanges, custody services (i.e. Services to which the user has entrusted access to coins), issuers of tokens and smart contracts.

Simply put, a freeze can occur when there is a third party between the user and the blockchain that is technically capable of restricting the free movement of money. That is, in a situation where decentralization is at risk.

Main reasons for freezing

In practice, crypto assets are usually frozen for the following reasons:

• As part of compliance: Centralized exchanges (CEX) or stablecoin issuers may temporarily restrict access to funds if suspicious activity is detected due to anti-money laundering (AML) and know your customer (KYC) regulatory requirements, as well as to comply with sanctions requirements or other legal restrictions.

• On user account security: Repeated unsuccessful login attempts, signs of hacking or unauthorized access often lead to an automatic blocking of transactions by the crypto exchange.

• Freezing at the smart contract level: Funds may be blocked due to errors in the code, protocol rules, or actions of the token issuer.

• Maintenance and outages: Scheduled maintenance, false positives from compliance algorithms, updates or technical errors on the platforms may temporarily suspend transfers and withdrawals.

Types of freezing

In practice, there are several main types of freezing of crypto assets. The first and most common problem is freezing on centralized platforms. Cryptocurrency exchanges and custodial services control access to user funds and may suspend transactions for individual accounts or addresses.

The second type is software freezing at the smart contract level. In this case, the possibility of restriction is built directly into the contract code. Issuers of stablecoins usually resort to a similar method. Some contracts initially provide for the possibility of blocking transfers, individual addresses or the entire system in an emergency.

In addition, sometimes a technical standstill occurs, which is not associated with legal decisions, but with errors. If no new blocks are generated on the blockchain, user funds can also be technically considered “frozen”. In the strict sense, this is not a “freeze” of assets, but a shutdown of the network. However, the term “freeze” is sometimes used in this sense.

How to freeze

Using the example of a centralized exchange, the freezing mechanism looks relatively simple. The user is not the direct owner of the private keys;in this case, they are stored by the platform. This means that the exchange is technically able at any time to prohibit the withdrawal of funds, block an account or restrict individual transactions. For this reason, storing cryptocurrencies in an exchange account is considered unsafe. This problem is not new and therefore many years ago the maxim expression became popular among crypto enthusiasts: “Not your keys, not your coins.”

For stablecoins issued via smart contracts, the situation is less simple. Many popular stablecoins contain features that allow the issuer to block specific addresses. A typical example is a feature such as Blacklist (address), which allows an issuer to blacklist a specific address. After that, all attempts to transfer tokens from such an address are blocked by the smart contract itself, although the tokens remain listed on the blockchain's balance sheetare.

For example, according to Blocksec, Tether blocked several thousand addresses on the Ethereum and Tron blockchains, freezing more than $2.9 billion in USDT.

From a technical perspective, this shows an important property: Even in a blockchain, the rules for the circulation of a token can be managed centrally if the logic of a specific smart contract provides for this.

Output

The freezing of crypto assets is not a feature of blockchain technology itself, but occurs at the level of the infrastructure surrounding the cryptocurrency: exchanges, custody services, issuers of tokens and smart contracts. The key risk factor in this context is the level of “custody” of the service. The closer a service comes to a custody model, the higher the risk that funds will be frozen, regardless of whether these are compliance requirements, security measures or technical limitationsis.