RSA Key Pair Generator

What Is an RSA Key Pair Generator?

In today’s digital landscape, data security and privacy protection have become top priorities for developers and organizations alike. Whether you are configuring SSH access, authenticating with GitHub, or building encrypted communication software, a secure and reliable RSA key pair is a fundamental requirement.

Our RSA Key Pair Generator is a tool that uses the RSA algorithm to generate a pair of mathematically related keys—a Public Key and a Private Key. It is designed to provide a fast, free, and highly secure online RSA generation experience, supporting industrial-grade key sizes of 1024, 2048, and up to 4096 bits.

• Public Key: Can be shared with anyone and is used to encrypt data or verify digital signatures.
• Private Key: Must be kept strictly confidential and is used to decrypt data encrypted with the public key or to create digital signatures.

This mechanism is known as Asymmetric Encryption, and it forms the foundation of modern Internet security protocols such as HTTPS/TLS, SSL, and SSH.

How the RSA Algorithm Works

RSA is based on a fundamental principle of number theory: multiplying two very large prime numbers is computationally easy, but factoring their product back into the original primes (the large integer factorization problem) is extremely difficult with current computing power. The core steps are as follows:

1. Choose Base Primes

Randomly select two distinct, very large prime numbers, denoted as $p$ and $q$.

2. Compute the Modulus and Euler’s Totient

• Compute the modulus $n$: The binary length of $n$ determines the key size (e.g., 2048 bits). The value of $n$ is public and is calculated as:

  $$n = p \times q$$

• Compute $\phi(n)$: According to Euler’s totient function, when $n$ is the product of two primes:

  $$\phi(n) = (p - 1)(q - 1)$$

3. Select the Encryption Exponent $e$

Choose an integer $e$ such that $1 < e < \phi(n)$ and $e$ is coprime with $\phi(n)$. In practice, to optimize encryption performance, $e$ is commonly set to the fixed value $65537$.

4. Compute the Decryption Exponent $d$

Calculate $d$ as the modular multiplicative inverse of $e$, satisfying the following congruence:

This means that $(e \cdot d - 1)$ is divisible by $\phi(n)$. The value $d$ is the core component of the private key—only someone who possesses $d$ can decrypt data encrypted with $e$. Therefore, $d$ must be kept strictly confidential.

5. Form the Key Pair

At this point, all essential parameters are available:

• Public Key: $(n, e)$
• Private Key: $(n, d)$

6. Encryption and Decryption Formulas

Once the key pair is generated, secure data transmission follows these rules:

• Encryption: Convert plaintext $M$ into ciphertext $C$:

  $$C = M^e \pmod n$$

• Decryption: Recover plaintext $M$ from ciphertext $C$:

  $$M = C^d \pmod n$$

Why Use RSA Encryption?

1. High Security: With a sufficiently large key size (2048 bits or higher is recommended), RSA is considered infeasible to break within any practical timeframe, even for modern supercomputers.
2. No Shared Secret Required: Unlike symmetric encryption, RSA does not require parties to exchange a secret key in advance, significantly reducing the risk of key leakage.
3. Authentication and Integrity: The private key holder can prove their identity through digital signatures, which recipients can verify using the public key to ensure the data has not been tampered with.

Why Choose Our Online RSA Generator?

When selecting an online tool, security is the primary concern. Our solution offers several clear advantages:

Security and Privacy First

Your private key never leaves your device. Many online tools generate keys on a server, meaning the server operator could potentially access your private key. In contrast, all cryptographic operations in our tool are performed locally in your browser and are never uploaded to any server, effectively eliminating the risk of private key leakage.

Multiple Key Length Options

• 1024 bit: Suitable for legacy systems with low security requirements (not recommended for sensitive data).
• 2048 bit: The current industry standard, balancing strong security with good performance.
• 4096 bit: Extremely strong encryption, ideal for long-term storage or environments with strict security requirements.

Standard PEM Output

Generated keys comply with PKCS#1 or PKCS#8 standards and are fully compatible with OpenSSH, OpenSSL, Java, Python, Go, and other development environments. They can be used directly as .pem or .key files.

Ready to Use, One-Click Refresh

A key pair is generated automatically as soon as the page loads. If you want a new one, simply click the “Refresh” button to regenerate instantly—no configuration required.

How to Generate Keys with This Tool

Generating a key pair takes just three simple steps:

1. Select the key length: Choose the desired size from the dropdown menu (default is 2048 bits).
2. View the results: The page automatically computes and displays the generated private key and public key. You can also click “Refresh” to generate a new pair.
3. Copy or download: Use the “Copy” icon or the “Download” button to save the keys to your local machine.

Security Tip: Always keep your private key secure. Never share it with anyone or upload it to public code repositories such as GitHub.

Best Practice: Hybrid Encryption

In real-world applications, RSA involves expensive large-integer exponentiation and is therefore not typically used to encrypt large amounts of data directly. Instead, industry best practice follows a hybrid encryption approach:

1. Encrypt data symmetrically: Generate a random symmetric key and use a fast symmetric algorithm (such as AES) to encrypt large volumes of plaintext data.
2. Encrypt the symmetric key: Use the recipient’s RSA public key to encrypt the symmetric key.
3. Send the payload: Transmit both the encrypted data and the RSA-encrypted symmetric key together.
4. Decrypt on receipt: The recipient first decrypts the symmetric key using their RSA private key, then uses that key to decrypt the data.

This approach combines the strong security of RSA with the high efficiency of AES.