Is Blockchain Fit For the Post-Quantum Future? There is a debate over whether **blockchain **can withstand **quantum attacks**. The current solutions involve adding quantum keys to blockchain software and encryption of all information. However, these measures are not a panacea for cyber threats. It is difficult to retrofit a classically-based blockchain to make it quantum-resistant. Moreover, the effort requires a significant amount of cash and time. For these reasons, governments should acknowledge that blockchain-based products are vulnerable to cyberattacks.

## Quantum-resistant algorithms

IBM, a global leader in health IT, is offering its customers the option to use **quantum-resistant** **cryptography**. This technology was developed following recommendations from the National Institute of Standards and Technology. This is crucial since future quantum computers are predicted to be even more powerful than current machines. It’s crucial to protect sensitive data such as health information from these machines.

NIST is currently evaluating different quantum-resistant public-key cryptographic algorithms. Among these is the **Stateful hash-based signature scheme** (XMSS). Companies and governments are also preparing for the threat from quantum computers. They estimate that a quantum computer will need about 2330 logical qubits to crack most public key cryptography.

Despite its distributed structure, blockchain is susceptible to attacks from malicious nodes. A malicious node can disrupt the generation of blocks. In addition, the **blockchain systems** can record malicious behaviors, which can influence the node’s score during elections. This decreases the probability of a malicious node being elected as a witness.

For a secure post-quantum future, it’s vital to develop algorithms that are immune to quantum damage. While many developers are working to improve their own quantum-resistant signature schemes, the **National Institute of Standards and Technology (NIST)** has started a process to standardize quantum-resistant algorithms. To date, NIST has shortlisted 26 algorithms for post-quantum cryptography.

In order to ensure the security of digital transactions, **Ethereum **must transition from SHA-256 to a quantum-resistant algorithm. This is crucial for the future of digital currency.

## XMSS

The **XMSS **blockchain is a stateful signature scheme, which is designed to be post-quantum secure. Although its primitives are similar to hash-based cryptosystems, it is more complicated than its predecessors. This is due to the fact that XMSS is built on a stateful signature scheme that is secure even when the system is susceptible to quantum attacks.

The difficulty of implementing **post-quantum cryptography** on small devices is due to the fact that they are not designed to hold a huge amount of data. This constraint makes it difficult to use post-quantum cryptography in these smaller devices, like smartcards and IoT devices.

However, XMSS has several advantages over its rivals. Its hash algorithm can be implemented in both C and non-optimized assembly instructions, simulating the constraints of automotive **ECUs**. This can improve the speed of signature verification. As a result, it can be competitive with Dilithium and EdDSA.

XMSS is also based on **SAFEcrypto**, which stands for Secure Architectures of Future Emerging Cryptography. This mathematical source has been designed to increase the security of public key encryption, digital signatures, and authentication schemes. This technology has the potential to increase speed and reduce energy consumption when running applications in low-power environments.

While this technology is still in its early days, there are many challenges ahead. It is still not clear whether or not it will be able to withstand the threat of quantum computers. The **Mosca theorem** says that we are likely to see quantum computers in the 2031 time frame.

There are several post-quantum Blockchain initiatives currently underway. These are highly computationally intensive, and therefore require high processing power. Hence, they are not yet practical to implement in practice. Further research is necessary to overcome the **technical challenges**.

## SPHINCS+

**SPHINCS+** is a stateless quantum-resistant signature algorithm. It offers a security level of 128 bits against quantum computers, and is suitable for blockchain environments. It is designed to be decentralized and distributed. It also prevents double-spending, making it a highly secure system.

In SPHINCS+, signatures are created using **FORS **trees. These trees are constructed from one or more public keys. The signatures are created by combining leaves of a FORS tree. The leaves are addressed with a random value, which mitigates side-channel attacks. SPHINCS+-256s has a maximum height of 16 million signatures.

Digital signatures secure login credentials and allow identity verification. The three algorithms selected by the NIST are **CRYSTALS-Dilithium**, **FALCON**, and SPHINCS+. Each serves a different purpose. CRYSTALS-Dilithium is a good choice for use as a primary algorithm, while FALCON is best suited for applications that need smaller signatures. SPHINCS+, on the other hand, is slower than the other two algorithms, but is useful as a backup algorithm. It is based on a different math approach than the other two algorithms.

Another key to secure the SPHINCS+ blockchain is its implementation of post-quantum cryptographic algorithms. This new generation of cryptography will require multiple algorithms, which can be based on different scenarios. For example, Kyber and Dilithium use structured lattices, while SPHINCS+ uses hash functions to ensure security. The **NIST **announcement is a great step towards quantum-safe technology. However, there are still several implementation challenges to overcome. One of these challenges is the large public-key size and the low verification and signing performance of current cryptographic algorithms.

The development of robust quantum computers is a **complex problem**. It is impossible to gauge the progress of quantum computers using simple metrics, such as computing power. It is likely that it will take 25 to 30 years for a quantum machine to reach the maximum power. But this is just a rough estimate. If quantum computers were to reach their potential, they would threaten public-key cryptography.

## Grover’s algorithm

In the post-quantum world, a cryptographic hash algorithm is more dangerous than an asymmetric one. It can compromise the integrity of a blockchain by allowing hackers to change the hash value of a block. Cryptographic hashing uses one-way hash functions to prevent tampering with data, but this security measure is not impenetrable to classical computers. However, a quantum attacker can theoretically find two inputs that produce the same hash value. This is called a “**hash collision**,” and could allow anyone to tamper with the blockchain.

In addition, quantum computers can break **public-key cryptosystems**. The ed25519 digital signature scheme, for instance, is vulnerable to quantum attacks. However, symmetric-key cryptosystems are not affected by this attack. While using Grover’s algorithm can significantly reduce the security of a blockchain, the risk can be mitigated by increasing the key-length. To do this, Hedera follows the CNSA standard.

**Grover’s algorithm** has the same properties as AES. It can decode a 10-character password in a matter of seconds, but it requires intensive error-correction. As a result, a quantum attacker with a large memory may be able to attack the algorithm.

The algorithm works with the idea of a large search space that contains large number of components. It is based on the idea that most of the components of a hash are not the golden nonce. By using a uniform superposition of the **search space**, Grover’s algorithm can extract the golden nonce with high probability.

Grover’s algorithm performs quantum search over black-box function that has been tested for security against preimage and collision attacks. However, it is slower than **Oechslin’s rainbow **tables and **van Oorschot-Wiener** algorithms. The algorithm is also more complex than the Oechslin’s rainbow tables, which are faster but more complicated to implement. The developers of Ethereum 2.0 Serenity have implemented a method that enables users to switch to a quantum-safe signature scheme.

## RANDAO

The **RANDAO blockchain** is designed to be robust against quantum attacks. To this end, it uses advanced cryptography techniques that have proven to be secure and fast. These include hash-based signature schemes, which are fast but also yield small signatures. Other methods such as XMSS utilize many one-time signatures that require state storage. SPHINCS signatures, on the other hand, use a small number of time signatures that are combined with Merkle trees. In this way, it does not require state storage and can be used repeatedly.

Asymmetric cryptography is another type of cryptography used in blockchains. In this case, the public key is only exposed for a short period between the announcement and the finalisation of a transaction. In this way, quantum computers cannot decrypt the output. By contrast, a **black-box algorithm** is a more powerful method that hides information in a block and links them together. This method is more secure than hashing algorithms, which are also easily broken by a quantum computer.

The **RANDAO **blockchain is also designed to withstand the threat posed by quantum computers. A quantum computer would need 2330 logical qubits to break most traditional public-key cryptography. In order to prevent this, the RANDAO blockchain uses a quantum resistant system called XMSS.

Quantum computing can be used to accelerate the speed of problem-solving. While the technology is still in its infancy, it will bring unimaginable advances in medicine and science. The biggest threat from **quantum technology** isn’t quantum power itself; it is the way in which we implement it. However, it is essential for organizations to prepare for this future.