Rivest Shamir Adleman

What Is RSA?

RSA is a public-key cryptographic algorithm that enables secure communication and identity verification using a pair of distinct keys. The public key is openly shared, functioning much like your “address,” while the private key must be kept confidential, akin to a “password” known only to you. Others can encrypt information using your public key, but only you can decrypt it with your private key. Similarly, you can sign messages with your private key, and anyone can use your public key to verify the signature’s authenticity and integrity.

How Does RSA Work?

RSA is based on the mathematical challenge of “factoring large integers.” The system generates two very large random prime numbers, multiplies them to produce a massive value that serves as the “core lock,” and then selects a complementary pair of exponents as the public and private keys. Encryption, decryption, signing, and signature verification fundamentally involve “raising the message to a power and taking a modulus with the core lock,” and then reversing the process as needed.

In practical implementations, mature cryptography libraries are used to handle key generation and cryptographic operations. Users only need to understand that the public key is for encryption and verification, while the private key is for decryption and signing; mathematical details are managed by the library.

How Is RSA Used in Web3?

In Web3, RSA is mainly used for off-chain security to bring trusted results on-chain. Typical use cases include:

• Securing HTTPS connections when accessing decentralized applications (dApps) or trading platforms. Browsers validate server certificates, which are commonly issued by trusted authorities and signed using RSA. As of 2025, RSA-2048 remains widely deployed for TLS certificate signatures, safeguarding communication between web or app clients and servers—for example, verifying server identity when accessing Gate websites or APIs.

• Signing wallet and node software distributions. When downloading wallets, plugins, or node applications, operating systems or package managers verify developer signatures—many ecosystems still use RSA certificates or keys to prevent tampering or malicious replacements.

• Privacy and cross-chain designs. Certain protocols employ RSA accumulators for “set membership proofs,” allowing compact verification that “an object belongs to a set.” This technique is applied in private asset management and collection synchronization.

How Are RSA Keys Generated and Managed?

Secure RSA begins with robust generation practices. First, keys must be generated using reliable sources of randomness—entropy acts as the “noise” behind drawing lots, and weak randomness can make keys guessable. The appropriate key length is also crucial: RSA-2048 is generally considered the minimum standard in the industry, while longer-term or high-security needs recommend RSA-3072 or above (as of 2025).

For storage, it’s best to keep private keys on hardware devices such as hardware wallets or dedicated hardware security modules (HSMs), which store keys within chips and restrict their export. Backups should be offline and encrypted, with multiple copies stored in separate locations. For team collaboration, a “threshold” approach can split the private key into several shares, requiring an agreed number to reconstruct it—reducing single-point risks.

When using keys, always protect private key files with strong passphrases, rotate keys and certificates regularly, revoke unused certificates, and avoid transmitting private keys over networks or instant messaging platforms.

How Does RSA Signing and Verification Work?

Digital signatures prove that “this message was sent by me and hasn’t been tampered with.” Verification allows recipients to check this using the sender’s public key.

1. Prepare the message to be signed and compute its hash—a hash functions as a “fingerprint,” compressing content into a fixed length for integrity checking.
2. Use the private key with an appropriate signature padding scheme to generate the signature. PSS padding is common; it wraps the message in a standard format to prevent structural attacks.
3. Send the message body, signature, and public key (or certificate containing it) to the recipient. Certificates endorsed by trusted authorities can prove ownership of a particular public key.
4. The recipient uses the public key, matching hash algorithm, and identical padding to verify authenticity. If all elements match, sender identity and message integrity are confirmed.

A typical example is software distribution: when downloading a wallet app, systems use a built-in certificate chain to verify developer signatures—often including RSA signatures.

What Is the Difference Between RSA and ECDSA?

Both are public-key cryptosystems but rely on different mathematical foundations and offer distinct performance profiles. RSA is based on the difficulty of factoring large integers; ECDSA relies on elliptic curve discrete logarithms. Generally, RSA signatures are larger but verify faster; ECDSA signatures are smaller, making them suitable for on-chain storage and bandwidth-sensitive scenarios.

On blockchains, Bitcoin and Ethereum accounts widely use elliptic curve signatures (ECDSA), so smart contracts and nodes natively support ECDSA. RSA verification on-chain usually requires big integer libraries or special precompiles—raising costs and complexity. Thus, RSA is more prevalent in off-chain communication, software signing, or as part of certain proof systems and toolchains.

What Are the Risks and Security Considerations of RSA?

Risks mainly arise from implementation details and misconfiguration. Firstly, encryption and signing must use proper “padding.” Encryption should adopt OAEP (adding randomness and structure protection), while signatures should use PSS—outdated padding schemes are vulnerable.

Weak randomness can make generated primes predictable, exposing keys to recovery attacks. Always use strong system entropy or hardware random sources. Also guard against side-channel attacks (e.g., timing or power analysis), utilizing constant-time implementations and hardware protections.

Key length is critical: as of 2025, RSA-2048 remains widely used, but long-term certificates or high-value assets should opt for RSA-3072 or higher. Avoid outdated hash algorithms; SHA-1 is no longer recommended for signatures.

Finally, quantum risk looms: scalable quantum computers running Shor’s algorithm could threaten both RSA and elliptic curve algorithms. It’s important to follow post-quantum cryptography migration plans and consider hybrid schemes combining traditional and post-quantum algorithms for appropriate use cases.

Asset security reminder: never upload private keys online or entrust them to third-party services; for wallets holding crypto assets, always prefer hardware wallets with secure offline backups.

How Is RSA Verified in Smart Contracts and On-Chain?

Most mainstream blockchains lack native RSA precompiles; performing large integer operations directly in contracts consumes significant gas or computational resources. Common approaches include:

• Off-chain verification with on-chain attestation: perform RSA verification on servers or clients first, then submit verification results, relevant hashes, and necessary credentials to the blockchain.
• Using chains or Layer 2 networks that offer RSA precompiles or efficient big integer libraries—keeping costs manageable.
• Leveraging zero-knowledge proofs: encapsulate “I have correctly verified an RSA signature” within a proof; only the proof itself is verified on-chain, avoiding direct heavy computation.

The choice depends on cost constraints, real-time requirements, and auditability needs.

What Are the Future Trends for RSA?

In the short term, RSA will remain a cornerstone of Internet and Web3 infrastructure—especially for TLS certificate signing, software distribution, and certain privacy tools. In the medium term, as post-quantum cryptography standards mature, more systems will implement hybrid verification combining “RSA/ECDSA + post-quantum” methods for smoother migration. Over the long run, integrating RSA accumulators with zero-knowledge toolchains may play significant roles in cross-chain state synchronization and large-scale set proofs.

RSA Key Points Recap & Extensions

RSA enables encryption and digital signatures using paired keys—public key is shared openly while private key remains confidential. In Web3 contexts, RSA is more often used for off-chain communication and software signing, as well as providing set membership proofs in specific protocols. Security best practices include robust randomness sources, appropriate key lengths, OAEP/PSS padding schemes, hardware protection, and sound certificate management. Due to quantum risks and on-chain costs, blockchain verification typically employs off-chain validation plus attestation, precompile support, or zero-knowledge proofs. Looking ahead, focus should remain on post-quantum migration strategies and hybrid deployment models with existing systems.

FAQ

What’s the difference between RSA encryption and digital signatures?

RSA encryption protects data confidentiality: public keys encrypt data so only holders of the corresponding private key can decrypt it. Digital signatures verify identity and integrity: private keys sign messages so anyone can confirm their origin via public key verification. On blockchains, transaction signing uses digital signature schemes such as RSA or alternatives to guarantee authenticity and immutability.

Why is RSA rarely used in cryptocurrencies?

RSA sees limited use in cryptocurrencies due mainly to efficiency concerns. Secure RSA requires 2048-bit (or longer) keys—resulting in slow computation and significant storage overhead. Algorithms like ECDSA achieve equivalent security with just 256-bit keys—offering much higher efficiency. Bitcoin and Ethereum both adopted ECDSA instead of RSA for their core signature mechanisms.

Why shouldn’t RSA key lengths be too short?

RSA’s security depends on the difficulty of factoring large numbers—the shorter the key length, the easier it becomes to break. Modern computing makes 1024-bit RSA unsafe; 2048 bits is now the minimum standard while high-security environments require 4096 bits or more. Longer keys offer stronger security but reduce performance—so balancing safety against speed is crucial.

How should individuals securely manage their RSA private keys in Web3 applications?

While Web3 primarily uses ECDSA rather than RSA, management principles are similar: never transmit private keys online; store them using hardware wallets or cold wallets offline; avoid screenshots or cloud syncing of backup phrases; audit access permissions regularly. For RSA-based identity verification or signing use cases, also protect private key files in secure isolated environments.

Does quantum computing threaten RSA security?

Yes—quantum computing poses a major threat to RSA. Shor’s algorithm could theoretically break RSA in polynomial time versus exponential time required by classical computers. This has motivated research into post-quantum cryptographic alternatives across academia and industry. For now, RSA remains safe for most applications—but long-term planning should include preparing blockchain infrastructure (and broader cryptography) for a quantum future—including migration strategies for blockchain systems.