The birth of Bitcoin in 2009 not only introduced a new type of digital asset, but also established an entirely new model of trust: decentralized trust based on mathematics instead of intermediary institutions. In the context of global digital transformation in 2025-2026, the question of blockchain security is no longer a simple binary issue. Blockchain security is a multi-layered architecture, combining theoretical cryptography, economic game theory, distributed network architecture, and complex software implementations. This report, compiled by the team of experts at Tan Phat Digital, undertakes a detailed analysis of the core components that make up the blockchain's protective armor, while also exposing potential cracks in the actual implementation.
Cryptographic infrastructure: The foundation of immutability
Blockchain's security system is built on two main cryptographic pillars: cryptographic hash functions (cryptographic hashing) and asymmetric cryptography. These components ensure that data cannot be tampered with and that ownership of assets is absolutely authenticated.
Cryptographic Hashing and Data Integrity
A hash function is an algorithm that converts a data input of any size into a fixed-length string of characters, called a "digital fingerprint" of that data. In blockchain architecture, hash functions act as the glue that binds blocks together. Each block contains the hash value of the previous block, forming a logically linked chain. The most important properties of a secure hash function, such as SHA-256, are pre-image resistance and collision resistance.
Mathematically, the hash function $H(x)$ must ensure that for any small change in $x$, the value of $H(x)$ will change unpredictably, a phenomenon known as the avalanche effect. If an attacker attempts to change the data in a historical block, the hash value of that block will change, resulting in the hash value stored in the next block becoming invalid. To successfully make a change without being detected by the network, an attacker must recalculate the hashes for all successive blocks faster than the entire network combined—an impossible task for large networks.
Asymmetric Cryptography and Digital Signatures
While hash functions protect the integrity of the ledger, asymmetric cryptography is responsible for protecting access and executing transactions. translate. This mechanism uses a pair of keys: a public key and a private key. The public key is like some bank account that can be shared publicly, while the private key acts as the ultimate cryptography to unlock and sign transactions.
According to analysis by Tan Phat Digital, important cryptographic features include:
Hashing (SHA-256): Converts data to a fixed 256-bit string to ensure absolute immutability of ledger.
Digital Signature (ECDSA): Authenticates transactions using a public/private key pair, ensuring non-repudiation.
Merkle Tree Structure: Hierarchical hash tree of data optimizes data integrity checking in large blocks.
PKI (Public Key Infrastructure): Key management framework and certificates to establish identity in permissioned networks.
However, this security depends entirely on keeping the private key secret. If the private key is lost or stolen, the asset is lost forever because the blockchain has no central mechanism to recover passwords.
See more: Rug Pull is What?
Consensus Mechanism: A Balance Between Economics and Engineering
Blockchain security is not just a matter of mathematics but also a matter of game theory. The consensus mechanism is the method by which nodes in the network achieve agreement on the state of the ledger in a trustless environment.
Proof of Work (PoW) and energy barriers
PoW forces miners to spend real energy resources to solve math problems. This creates a huge attack cost. To reverse a transaction on Bitcoin, an attacker needs to control more than 50% of the total hashing power (hashrate) of the network. By early 2026, the estimated cost of a 51% attack on the Bitcoin network had increased to around $10 billion due to mining difficulty and increased equipment value. While it is theoretically possible, economic incentives make it much more profitable to participate in protecting the network than sabotaging it.
Proof of Stake (PoS) and financial sanctions mechanisms
PoS replaces the expenditure of energy with the deposit of assets (staking). The security of PoS is based on the value of the locked assets. If a validator tries to cheat, the network will implement a "slashing" mechanism (asset confiscation). For the Ethereum network, the cost to carry out a similar attack (34% or 51% attack) in 2026 is estimated to be up to 44.8 billion USD due to the extremely large amount of ETH staked.
See more: What is a 51% attack?
Analysis of consensus models from Tan Phat Digital:
Proof of Work: Safety threshold below 50% of computing power. Low performance (7-15 TPS) but very high level of decentralization.
Proof of Stake: Safety threshold from 33% to 50% of staked assets. Medium to high performance with a high degree of decentralization.
CFT (Crash Fault Tolerance - e.g. Raft): Safety threshold below 50% of nodes experiencing power failure. Very high performance (over 3000 TPS) but low level of decentralization, mainly used within businesses.
BFT (Byzantine Fault Tolerance - for example SmartBFT): Safety threshold below 33% of nodes acting maliciously. High performance (about 2000 TPS), suitable for enterprise alliances.
Network layer attack scenarios and P2P structural vulnerabilities
Blockchain operates on a peer-to-peer (P2P) network, where information is propagated through connections between nodes. This is where network layer vulnerabilities arise:
Eclipse Attack (Node Isolation): An attacker takes full control of a node's connections, providing a distorted view of the blockchain state to that target.
Sybil Attack (Multiple Fake Identity): Generates a series of fake identities to overwhelm the network's voting or consensus process mesh.
Routing attacks: Target ISP infrastructure to split the network into isolated segments, risking transaction reversals when connectivity is restored.
Smart Contract Security and Bridge Risk
As blockchain becomes the foundation for smart contracts, risk shifts to the application layer. A small programming error can cause a huge loss of assets that cannot be recovered. A typical example is the Bybit hack in February 2025, where hackers withdrew ETH worth 1.4 billion USD through taking control of the signing-key of multi-sig wallets.
In-depth security audit process recommended by Tan Phat Digital:
Preparation Phase: Implement source code freeze (Code Freeze) and complete technical documents.
Automatic scanning: Uses AI and static analysis tools to quickly detect common errors such as Reentrancy or Overflow.
Manual review: A team of experts reads code line by line to look for complex logic flaws that machines miss.
Error analysis and ranking: Sort by severity level (Critical, High, Medium, Minor) to prioritize handling.
Reporting and Retesting:Fix errors and perform retesting (Retest) to ensure absolute safety before Mainnet.
Wallet security and key management in 2026
The year 2026 records the explosion of technology Examination Account Abstraction and Multi-Party Computing (MPC). According to experts from Tan Phat Digital, these solutions help eliminate the "single point of failure" of traditional private keys:
Multi-Party Computation (MPC): Split the private key into shares (shares) stored in multiple places. No single entity holds the entire key, reducing the risk of centralized hacking.
Account Abstraction (ERC-4337): Enables the wallet to act as a smart contract, supporting social account recovery, setting spending limits, and signing transactions using biometrics.
Quantum Computing and Post-Quantum Cryptography (PQC)
Quantum Computing is getting closer to being able to break current cryptographic algorithms. Tan Phat Digital updates post-quantum solutions being researched:
For ECDSA (Bitcoin/ETH): Risk of being broken by Shor algorithm. The solution is to switch to CRYSTALS-Dilithium or Falcon.
For SHA-256 (Mining): Efficiency is reduced by the Grover algorithm. The solution is to increase the hash length to SHA-512.
"Harvest Now, Decrypt Later" strategy: Attackers are collecting encrypted data today to wait for decryption by quantum computers in the future, requiring networks to upgrade PQC now.
Context in Vietnam: Digital Technology Industry Law 2026
From January 1, 2026, the Digital Technology Industry Law officially takes effect in Vietnam, bringing a clear legal framework for digital assets:
Legal identification: Digital assets and encrypted assets are recognized as legal property rights according to the Civil Code.
Risk prevention P2P:Participants in peer-to-peer transactions need to be careful not to accidentally participate in money laundering and tax evasion activities, leading to the risk of having their bank accounts blocked.
Crime suppression: Vietnamese authorities (such as A05) have destroyed many large-scale fraud rings such as the Paynet Coin (PAYN) case that caused billions of dollars in damage, using variable multi-level models general in cyberspace.
Typical attacks and scams (Case Studies)
To better understand actual vulnerabilities, Tan Phat Digital analyzes 10 typical cases that have occurred:
Bybit (February 2025): This is the largest digital asset theft in history with a loss of 1.4 billion USD. Hackers appropriated 401,000 ETH from Safe-multisig-based multi-signature wallets through signing key compromise or internal phishing attacks.
Paynet Coin Network (Vietnam): The largest Ponzi scam in Vietnam with total estimated losses of up to 2 billion USD. The ringleader uses platforms like FMCPAY to promise interest rates of 5-9% per month, defrauding tens of thousands of investors.
Ronin Bridge (Axie Infinity): The shocking bridge hack in 2022 caused 600 million USD in damage. The reason is that hackers took control of 5 out of 9 authentication nodes through a social engineering attack on employees.
Poly Network: $611 million exploit due to lack of input data validation in cross-chain transactions. Hackers took advantage of the loophole to change control of the contract and transfer funds to personal wallets.
Cetus DEX (Sui Ecosystem): 223 million USD loss due to logic error in handling fake tokens. Attackers created "spoofed" tokens to manipulate prices in liquidity pools and drain real assets.
Balancer V2: $128 million loss due to rounding error in stable pools. Hackers repeat the deposit/withdrawal cycle continuously to profit from small accounting errors.
KyberSwap (Vietnam): This Vietnamese-based decentralized exchange suffered losses of about 50 million USD in 2023. The incident is a warning about the urgency of cybersecurity for domestic blockchain projects.
Ethereum Classic (ETC) - 51% attack: ETC suffered many network control attacks in 2019 and 2020, causing losses of more than 6.7 million USD through double-spending.
Lykke Exchange: The UK exchange was attacked by the hacker group Lazarus Group in June 2024, taking 23 million USD. The incident shows the dangers of government-sponsored hacker groups targeting blockchain infrastructure.
Bitcoin Gold (BTG): Suffered 51% attack in 2018 and 2020, loss of about 18 million USD. The attacker rented hashing power from the NiceHash service to overwhelm the network and perform double-spend on exchanges.
Frequently Asked Questions (FAQ)
Here are the 10 most common questions about blockchain security and regulation in 2026, answered by the Tan Phat Digital team:
1. Is Blockchain really absolutely secure? No system is 100% secure. Blockchain is very secure at the protocol level thanks to encryption and decentralization, but can still be attacked through application source code errors (DEX, Lending), 51% attacks in small networks or due to user key management errors.
2. Is it legal to invest in cryptocurrency in Vietnam from 2026? Legal from the perspective of investment and exchange assets. Digital Technology Industry Law 2025 (effective January 1, 2026) recognizes virtual assets as a type of digital asset used for investment, but cannot be used as a means of payment to replace currency.
3. Do I have to pay tax when trading cryptocurrency in Vietnam? Yes. Digital assets are considered commercial activities. Individuals may be subject to personal income tax (PIT), while businesses may be subject to value added tax (VAT) and corporate income tax (CIT) when generating income from the purchase, sale or exchange of these assets.
4. Should I use a hot wallet or a cold wallet for the best security? Cold wallets (e.g. Ledger, Trezor) are the optimal choice for long-term asset storage because they are completely isolated from the internet, resistant to malware. Hot wallets should only be used for small daily transactions.
5. What is a 51% attack and how much does it cost? This is when one entity controls more than 50% of the mining/staking power to manipulate the network. In 2026, the cost of attacking Bitcoin is estimated at $6-10 billion USD, making it economically unviable for large networks.
6. How to recognize a fraudulent Blockchain project? The most common signs are the commitment to unusually high fixed profits (over 30%/month), the hierarchical compensation model (multi-level variation) and the request to deposit entrusted money into closed Telegram/WhatsApp groups.
7. Can quantum computers "break" Bitcoin in the near future? In theory it is possible through the Shor algorithm. However, experts estimate computers with 1,700 to 25,000 logical qubits would be needed to do this, a milestone that is still far off. The industry is actively turning to post-quantum cryptography (PQC) to cope.
8. Why is smart contract auditing important? Because the code on the blockchain is immutable. Audit helps detect logic errors such as "Reentrancy" or number overflow before deployment, preventing hackers from draining funds from DeFi protocols.
9. What are the risks of cross-chain bridges?Bridges are often the most attacked targets due to the complexity of locking one chain asset and minting another chain asset. The risk often lies in the validators' signing keys being compromised or logic errors in smart contracts.
10. How does Account Abstraction (AA) change wallet security? AA turns the wallet into a programmable smart contract. This allows users to restore wallets without the need for a 12-character seed phrase, set spending limits, and sign transactions using biometrics such as FaceID.
Blockchain is not absolutely impenetrable, but it provides the strongest multi-layered security system available today. Tan Phat Digital believes that blockchain security in 2026 is no longer just a battle of cryptography, but a combination of legal compliance, strict source code inspection and each user's security awareness. The transition from faith in people to faith in mathematics is still an inevitable trend of the future.
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