RSA Key Generator - Public Key Cryptography Tool

Executive Summary

What is the RSA Key Generator?

The RSA Key Generator is a professional cryptographic tool for creating RSA (Rivest-Shamir-Adleman) public-private key pairs, the foundation of modern public-key cryptography. This browser-based tool generates secure asymmetric encryption keys used for digital signatures, secure communications, SSL/TLS certificates, and encrypted data exchange across the internet.

Who Should Use This Tool?

Primary Audiences:

Developers: Generate keys for API authentication, JWT signing, SSH access, and encryption systems
DevOps Engineers: Create SSH keys for server access, deployment automation, and CI/CD pipelines
Security Professionals: Generate keys for certificate signing, secure communications, and PKI infrastructure
System Administrators: Create keys for email encryption (PGP/GPG), server authentication, and VPN access
Blockchain Developers: Generate keys for cryptocurrency wallets and smart contract signing

Key Capabilities

✅ Multiple Key Sizes: 2048-bit (fast), 3072-bit (balanced), 4096-bit (maximum security) ✅ Industry Standards: PKCS#1 and PKCS#8 format support for maximum compatibility ✅ Client-Side Generation: All operations in your browser - no server communication ✅ Multiple Export Formats: PEM, DER, JSON Web Key (JWK), SSH public key, XML ✅ Key Analysis: Detailed key information including modulus, exponents, and fingerprints ✅ Security Validation: Key strength verification and security recommendations ✅ Quick Generation: Optimized algorithms for fast key creation ✅ Download & Copy: Easy export with secure clipboard handling

When to Use RSA Keys

Digital Signatures: Sign documents, code, and transactions cryptographically
SSL/TLS Certificates: Secure websites with HTTPS encryption
SSH Authentication: Passwordless server access with public key authentication
Email Encryption: PGP/GPG encrypted email communications
API Authentication: OAuth, JWT token signing and verification
Code Signing: Verify software authenticity and integrity
Key Exchange: Securely share symmetric encryption keys (hybrid cryptography)
Blockchain: Cryptocurrency wallets and transaction signing

Quick Start (60 Seconds)

Select key size: Choose 2048, 3072, or 4096 bits (2048 recommended for most uses)
Click “Generate Keys”: Wait 1-5 seconds for cryptographic key generation
Review key information: Check key fingerprint and security details
Download keys: Save both private and public keys separately
Secure private key: Store in password manager or encrypted storage

Security Warning: Your private key is extremely sensitive. Anyone with access to your private key can decrypt your messages and impersonate you. Never share it or store it unencrypted.

Feature Tour

1. Key Generation Interface

Key Size Selection

🔐 Key Size Options:
├── 2048-bit (Recommended)
│   ├── Fast generation (<2 seconds)
│   ├── Widely supported
│   ├── Sufficient for most applications
│   └── RSA-2048: Secure until ~2030
│
├── 3072-bit (Enhanced Security)
│   ├── Medium generation time (3-7 seconds)
│   ├── Enhanced security margin
│   ├── Equivalent to AES-128
│   └── Recommended for long-term data (2030-2040)
│
└── 4096-bit (Maximum Security)
    ├── Slower generation (5-15 seconds)
    ├── Maximum security available
    ├── Equivalent to AES-192
    ├── Recommended for high-value assets
    └── Secure beyond 2040

Generation Process

Visual progress indicator during key creation
Entropy collection from system randomness
Prime number generation and testing
Key pair validation and verification
Automatic fingerprint calculation

2. Key Display and Information

Private Key Display

-----BEGIN RSA PRIVATE KEY-----
MIIEpAIBAAKCAQEAu7WoKhLmTvJbTG4rI5xV3CqH8x9y3PfO2J1kL7dN8mR4...
[Multiple lines of Base64-encoded key data]
...sK9pQ2vX3jR8yL4mN5oP6qR7sT8uV9wX0yZ1aB2cD3eF4gH==
-----END RSA PRIVATE KEY-----

Key Details:
• Format: PKCS#1 PEM
• Key Size: 2048 bits
• Modulus Length: 617 digits
• Public Exponent: 65537
• Created: 2025-11-03 07:14:32 UTC

Public Key Display

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAu7WoKhLmTvJbTG4r...
[Base64-encoded public key data]
...I5xV3CqH8x9y3PfO2J1kL7dN8mR4QIDAQAB
-----END PUBLIC KEY-----

SSH Format:
ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDCpT... generated-key

Fingerprint:
SHA256: 2c:3d:4e:5f:6a:7b:8c:9d:0e:1f:2a:3b:4c:5d:6e:7f

3. Key Format Options

Private Key Formats

Export Options:
├── PEM (PKCS#1) - Default
│   └── "-----BEGIN RSA PRIVATE KEY-----"
│
├── PEM (PKCS#8)
│   └── "-----BEGIN PRIVATE KEY-----"
│
├── DER (Binary)
│   └── Raw binary format for certificates
│
├── JSON Web Key (JWK)
│   └── { "kty": "RSA", "n": "...", "e": "...", "d": "..." }
│
└── XML
    └── <RSAKeyValue><Modulus>...</Modulus>...</RSAKeyValue>

Public Key Formats

Export Options:
├── PEM (PKCS#1)
│   └── "-----BEGIN RSA PUBLIC KEY-----"
│
├── SSH Public Key
│   └── ssh-rsa AAAAB3NzaC1yc2E...
│
├── JSON Web Key (JWK)
│   └── { "kty": "RSA", "n": "...", "e": "..." }
│
├── XML
│   └── <RSAKeyValue><Modulus>...</Modulus></RSAKeyValue>
│
└── OpenSSH Authorized Keys Format
    └── Ready for ~/.ssh/authorized_keys

4. Security Features

Key Validation

✅ Prime number strength verification
✅ Modulus size validation
✅ Public exponent verification (e = 65537)
✅ Key pair consistency check
✅ Security recommendations display

Security Indicators

🔒 Security Assessment:
├── ✅ Key Size Adequate (2048+ bits)
├── ✅ Strong Prime Numbers
├── ✅ Standard Public Exponent
├── ✅ Key Pair Verified
└── ⚠️ Recommendation: Store private key securely

Privacy Protection

All generation occurs client-side (browser)
No network communication during generation
No key storage or logging
Secure memory handling
Clear button for immediate key removal

5. Key Analysis Tools

Fingerprint Display

Fingerprint Formats:
├── SHA256: 2c:3d:4e:5f:6a:7b:8c:9d:0e:1f:2a:3b:4c:5d:6e:7f
├── MD5: a1:b2:c3:d4:e5:f6:07:18:29:3a:4b:5c:6d:7e:8f:90
└── SHA-1: 12:34:56:78:9a:bc:de:f0:12:34:56:78:9a:bc:de:f0:12:34:56:78

Key Components

RSA Key Structure:
{
  modulus: "Large number (n = p × q)",
  publicExponent: "65537 (e)",
  privateExponent: "Secret number (d)",
  prime1: "First prime (p)",
  prime2: "Second prime (q)",
  exponent1: "d mod (p-1)",
  exponent2: "d mod (q-1)",
  coefficient: "q^-1 mod p"
}

6. Import and Conversion Tools

Import Existing Keys

Paste existing PEM-format private key
Convert between formats (PEM ↔ JWK ↔ XML)
Extract public key from private key
Validate imported key integrity

Format Conversion

Input Format → Output Format
├── PEM → JWK
├── PEM → SSH Public Key
├── JWK → PEM
├── Private Key → Public Key
└── Any Format → Fingerprints

Usage Scenarios

Scenario 1: SSH Authentication Setup

Challenge: Password-based SSH authentication is vulnerable to brute-force attacks and phishing.

Solution: Public key authentication provides passwordless, secure server access.

Steps:

Generate SSH Key Pair

# Using our tool:
- Select 2048-bit or 4096-bit key size
- Click "Generate Keys"
- Download both private and public keys

Save Private Key Securely

# Linux/Mac
mv downloaded_private_key ~/.ssh/id_rsa
chmod 600 ~/.ssh/id_rsa

# Windows
# Save to C:\Users\YourName\.ssh\id_rsa

Add Public Key to Server

# Copy public key to server (SSH format)
# On server:
mkdir -p ~/.ssh
chmod 700 ~/.ssh
echo "ssh-rsa AAAAB3NzaC1yc2E..." >> ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

Test Connection

ssh -i ~/.ssh/id_rsa user@yourserver.com
# No password required!

Benefits:

Eliminates password-based attacks
Enables automated deployments
Simplifies key rotation
Provides audit trail through key fingerprints

Scenario 2: JWT Token Signing (API Authentication)

Challenge: Secure API authentication requiring token verification across distributed services.

Implementation:

// 1. Generate RSA key pair (use our tool for 2048-bit keys)

// 2. Server-side: Sign JWT with private key
const jwt = require('jsonwebtoken');
const fs = require('fs');

const privateKey = fs.readFileSync('private_key.pem');

function createToken(userId) {
  const payload = {
    sub: userId,
    iat: Math.floor(Date.now() / 1000),
    exp: Math.floor(Date.now() / 1000) + (60 * 60) // 1 hour
  };
  
  return jwt.sign(payload, privateKey, {
    algorithm: 'RS256'
  });
}

const token = createToken(12345);
console.log('Token:', token);

// 3. Client: Receive and use token
// Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...

// 4. Other services: Verify with public key only
const publicKey = fs.readFileSync('public_key.pem');

function verifyToken(token) {
  try {
    const decoded = jwt.verify(token, publicKey, {
      algorithms: ['RS256']
    });
    return { valid: true, userId: decoded.sub };
  } catch (error) {
    return { valid: false, error: error.message };
  }
}

const verification = verifyToken(token);
if (verification.valid) {
  console.log('Authenticated user:', verification.userId);
}

Advantages:

Public key can be shared safely with all services
Private key stays secure on authentication server
No shared secrets to distribute
Easy key rotation

Scenario 3: Email Encryption (PGP/GPG)

Challenge: Send confidential information via email securely.

Setup:

Generate Keys
- Use 4096-bit for maximum security
- Download both keys

Import to GPG

# Import private key
gpg --import private_key.pem

# Import public key
gpg --import public_key.pem

# List keys
gpg --list-keys

Share Public Key

# Export for sharing
gpg --armor --export your.email@example.com > public_key.asc

# Share via:
# - Email signature
# - Company website
# - Key servers: gpg --send-keys KEY_ID

Encrypt Email

# Encrypt message
gpg --encrypt --recipient recipient@example.com message.txt

# Encrypted output: message.txt.gpg

Decrypt Received Email

# Decrypt with your private key
gpg --decrypt encrypted_message.gpg > decrypted.txt

Use Cases: Legal documents, financial information, medical records, confidential business communications.

Scenario 4: Code Signing

Challenge: Users need to verify software hasn’t been tampered with.

Implementation:

# 1. Generate 4096-bit RSA key pair

# 2. Sign your application
openssl dgst -sha256 -sign private_key.pem \
  -out application.sig application.exe

# 3. Distribute application + signature + public key

# 4. Users verify signature
openssl dgst -sha256 -verify public_key.pem \
  -signature application.sig application.exe

# Output: "Verified OK" or "Verification Failure"

Applications:

Software distribution
Mobile app signing (iOS/Android)
Browser extensions
Firmware updates
Docker image signing

Scenario 5: Secure Key Exchange (Hybrid Encryption)

Challenge: Encrypt large files efficiently while maintaining security of key exchange.

Solution: Use RSA to exchange AES key, then AES to encrypt data.

// 1. Generate RSA key pair (2048-bit)

// 2. Sender: Generate AES key and encrypt data
const aesKey = generateRandomKey(256); // 256-bit AES key
const encryptedData = encryptAES(largeFile, aesKey);

// 3. Sender: Encrypt AES key with recipient's RSA public key
const encryptedAESKey = encryptRSA(aesKey, recipientPublicKey);

// 4. Send both encrypted data and encrypted key
send({
  encryptedData: encryptedData,
  encryptedKey: encryptedAESKey
});

// 5. Recipient: Decrypt AES key with RSA private key
const decryptedAESKey = decryptRSA(encryptedAESKey, myPrivateKey);

// 6. Recipient: Decrypt data with AES key
const decryptedData = decryptAES(encryptedData, decryptedAESKey);

Why Hybrid:

RSA is slow for large data
AES is fast but requires secure key exchange
Hybrid approach combines best of both

Use our AES Encryptor/Decryptor for the symmetric encryption portion.

Scenario 6: Blockchain Wallet Creation

Challenge: Create secure cryptocurrency wallet with public address and private key.

Implementation:

// 1. Generate RSA key pair (or use ECDSA for efficiency)

// 2. Derive wallet address from public key
const crypto = require('crypto');

function createWalletAddress(publicKey) {
  // Hash public key
  const sha256 = crypto.createHash('sha256').update(publicKey).digest();
  const ripemd160 = crypto.createHash('ripemd160').update(sha256).digest();
  
  // Add version byte (0x00 for Bitcoin mainnet)
  const versionedHash = Buffer.concat([Buffer.from([0x00]), ripemd160]);
  
  // Double SHA-256 for checksum
  const checksum = crypto.createHash('sha256')
    .update(crypto.createHash('sha256').update(versionedHash).digest())
    .digest()
    .slice(0, 4);
  
  // Concatenate and encode in Base58
  const addressBytes = Buffer.concat([versionedHash, checksum]);
  return base58Encode(addressBytes);
}

const walletAddress = createWalletAddress(publicKey);
console.log('Wallet Address:', walletAddress);
// Output: 1A1zP1eP5QGefi2DMPTfTL5SLmv7DivfNa

// 3. Sign transactions with private key
function signTransaction(transaction, privateKey) {
  const hash = crypto.createHash('sha256').update(transaction).digest();
  const signature = crypto.sign('sha256', hash, privateKey);
  return signature;
}

Security Critical: Losing private key means losing access to all funds. Never share private key.

Code Examples and Integration

Node.js Implementation

const crypto = require('crypto');
const fs = require('fs');

// Generate RSA key pair
function generateRSAKeyPair(keySize = 2048) {
  const { publicKey, privateKey } = crypto.generateKeyPairSync('rsa', {
    modulusLength: keySize,
    publicKeyEncoding: {
      type: 'spki',
      format: 'pem'
    },
    privateKeyEncoding: {
      type: 'pkcs8',
      format: 'pem'
    }
  });
  
  return { publicKey, privateKey };
}

// Encrypt data with public key
function encryptWithPublicKey(data, publicKey) {
  const buffer = Buffer.from(data, 'utf8');
  const encrypted = crypto.publicEncrypt(
    {
      key: publicKey,
      padding: crypto.constants.RSA_PKCS1_OAEP_PADDING,
      oaepHash: 'sha256'
    },
    buffer
  );
  return encrypted.toString('base64');
}

// Decrypt data with private key
function decryptWithPrivateKey(encryptedData, privateKey) {
  const buffer = Buffer.from(encryptedData, 'base64');
  const decrypted = crypto.privateDecrypt(
    {
      key: privateKey,
      padding: crypto.constants.RSA_PKCS1_OAEP_PADDING,
      oaepHash: 'sha256'
    },
    buffer
  );
  return decrypted.toString('utf8');
}

// Sign data
function signData(data, privateKey) {
  const sign = crypto.createSign('SHA256');
  sign.update(data);
  sign.end();
  return sign.sign(privateKey, 'base64');
}

// Verify signature
function verifySignature(data, signature, publicKey) {
  const verify = crypto.createVerify('SHA256');
  verify.update(data);
  verify.end();
  return verify.verify(publicKey, signature, 'base64');
}

// Usage example
const { publicKey, privateKey } = generateRSAKeyPair(2048);

// Encryption
const message = "Confidential information";
const encrypted = encryptWithPublicKey(message, publicKey);
console.log('Encrypted:', encrypted);

const decrypted = decryptWithPrivateKey(encrypted, privateKey);
console.log('Decrypted:', decrypted);

// Digital signature
const document = "Important contract terms...";
const signature = signData(document, privateKey);
console.log('Signature:', signature);

const isValid = verifySignature(document, signature, publicKey);
console.log('Signature valid:', isValid);

Python Implementation

from cryptography.hazmat.primitives.asymmetric import rsa, padding
from cryptography.hazmat.primitives import serialization, hashes
from cryptography.hazmat.backends import default_backend
import base64

# Generate RSA key pair
def generate_rsa_keypair(key_size=2048):
    private_key = rsa.generate_private_key(
        public_exponent=65537,
        key_size=key_size,
        backend=default_backend()
    )
    
    public_key = private_key.public_key()
    
    # Serialize to PEM format
    private_pem = private_key.private_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PrivateFormat.PKCS8,
        encryption_algorithm=serialization.NoEncryption()
    )
    
    public_pem = public_key.public_bytes(
        encoding=serialization.Encoding.PEM,
        format=serialization.PublicFormat.SubjectPublicKeyInfo
    )
    
    return {
        'private_key': private_pem.decode('utf-8'),
        'public_key': public_pem.decode('utf-8')
    }

# Encrypt with public key
def encrypt_with_public_key(message, public_key_pem):
    public_key = serialization.load_pem_public_key(
        public_key_pem.encode('utf-8'),
        backend=default_backend()
    )
    
    encrypted = public_key.encrypt(
        message.encode('utf-8'),
        padding.OAEP(
            mgf=padding.MGF1(algorithm=hashes.SHA256()),
            algorithm=hashes.SHA256(),
            label=None
        )
    )
    
    return base64.b64encode(encrypted).decode('utf-8')

# Decrypt with private key
def decrypt_with_private_key(encrypted_message, private_key_pem):
    private_key = serialization.load_pem_private_key(
        private_key_pem.encode('utf-8'),
        password=None,
        backend=default_backend()
    )
    
    decrypted = private_key.decrypt(
        base64.b64decode(encrypted_message),
        padding.OAEP(
            mgf=padding.MGF1(algorithm=hashes.SHA256()),
            algorithm=hashes.SHA256(),
            label=None
        )
    )
    
    return decrypted.decode('utf-8')

# Sign data
def sign_data(data, private_key_pem):
    private_key = serialization.load_pem_private_key(
        private_key_pem.encode('utf-8'),
        password=None,
        backend=default_backend()
    )
    
    signature = private_key.sign(
        data.encode('utf-8'),
        padding.PSS(
            mgf=padding.MGF1(hashes.SHA256()),
            salt_length=padding.PSS.MAX_LENGTH
        ),
        hashes.SHA256()
    )
    
    return base64.b64encode(signature).decode('utf-8')

# Verify signature
def verify_signature(data, signature, public_key_pem):
    public_key = serialization.load_pem_public_key(
        public_key_pem.encode('utf-8'),
        backend=default_backend()
    )
    
    try:
        public_key.verify(
            base64.b64decode(signature),
            data.encode('utf-8'),
            padding.PSS(
                mgf=padding.MGF1(hashes.SHA256()),
                salt_length=padding.PSS.MAX_LENGTH
            ),
            hashes.SHA256()
        )
        return True
    except:
        return False

# Usage
keys = generate_rsa_keypair(2048)
print("Generated RSA key pair")

message = "Confidential data"
encrypted = encrypt_with_public_key(message, keys['public_key'])
print(f"Encrypted: {encrypted}")

decrypted = decrypt_with_private_key(encrypted, keys['private_key'])
print(f"Decrypted: {decrypted}")

signature = sign_data(message, keys['private_key'])
is_valid = verify_signature(message, signature, keys['public_key'])
print(f"Signature valid: {is_valid}")

Troubleshooting

Common Issues and Solutions

Issue 1: Key Generation Takes Too Long

Symptoms: Browser appears frozen during 4096-bit key generation.

Causes:

Large key size requires extensive prime number generation
Older/slower devices have limited computational power
Browser tab backgrounded (lower priority)

Solutions:

1. Use 2048-bit keys for most applications
   - Sufficient security for 10+ years
   - 5-10x faster generation
   - Widely compatible

2. Keep browser tab active during generation
   - Browsers throttle background tabs
   - Keep window focused and visible

3. Use modern browser
   - Chrome, Firefox, Edge (latest versions)
   - Hardware acceleration enabled
   - WebCrypto API support

4. For production: Use server-side generation
   - OpenSSL command line
   - Dedicated key generation services
   - Hardware security modules (HSM)

Issue 2: “Insecure Key” Warning

Symptoms: Tool displays security warning after generation.

Possible Causes:

Generated 1024-bit key (deprecated)
Weak random number generation
Non-standard public exponent

Solutions:

✅ Use minimum 2048-bit keys
✅ Ensure browser supports WebCrypto API
✅ Use standard public exponent (65537)
✅ Regenerate if warning appears

Issue 3: Private Key Won’t Import

Symptoms: Error when importing existing private key.

Causes:

Incorrect format (not PEM)
Password-protected key
Corrupted key data
Wrong key type (EC, DSA instead of RSA)

Solutions:

# Convert password-protected to unprotected
openssl rsa -in encrypted_key.pem -out decrypted_key.pem

# Convert DER to PEM
openssl rsa -inform DER -outform PEM -in key.der -out key.pem

# Verify key format
openssl rsa -in key.pem -text -noout

# Extract public key from private key
openssl rsa -in private_key.pem -pubout -out public_key.pem

Issue 4: SSH Key Not Working

Symptoms: SSH still asks for password despite key setup.

Checklist:

# 1. Verify private key permissions (must be 600)
chmod 600 ~/.ssh/id_rsa
ls -la ~/.ssh/id_rsa
# Should show: -rw------- (owner read/write only)

# 2. Verify public key is on server
ssh user@server "cat ~/.ssh/authorized_keys"
# Should contain your public key

# 3. Check SSH configuration
ssh -v user@server
# Look for "Offering public key" messages

# 4. Verify server permissions
# On server:
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

# 5. Check SELinux context (if applicable)
restorecon -R ~/.ssh

Issue 5: JWT Verification Fails

Symptoms: “Invalid signature” error when verifying JWT tokens.

Common Mistakes:

// ❌ Wrong: Using private key to verify
jwt.verify(token, privateKey); // Will fail!

// ✅ Correct: Use public key to verify
jwt.verify(token, publicKey, { algorithms: ['RS256'] });

// ❌ Wrong: Mismatched algorithm
jwt.sign(payload, privateKey, { algorithm: 'HS256' }); // Symmetric algorithm

// ✅ Correct: Use RSA algorithm
jwt.sign(payload, privateKey, { algorithm: 'RS256' });

// ❌ Wrong: PEM format mismatch
const key = fs.readFileSync('key.pem', 'utf8').trim(); // Missing header/footer

// ✅ Correct: Full PEM format with headers
// -----BEGIN PRIVATE KEY-----
// ...key data...
// -----END PRIVATE KEY-----

Accessibility Features

Keyboard Navigation:

Tab - Navigate between controls
Space/Enter - Activate buttons
Ctrl/Cmd + C - Copy selected key
Escape - Close modal dialogs

Screen Reader Support:

ARIA labels on all controls
Status announcements for key generation
Progress indicators with text descriptions
Error messages with remediation steps

Visual Accessibility:

High contrast key display
Adjustable font sizes
Color-blind friendly indicators
Clear visual hierarchy

Frequently Asked Questions

1. What’s the difference between RSA and AES encryption?

RSA (Asymmetric):

Two keys: public (encrypt) and private (decrypt)
Slow performance
Small data only (up to key size)
Used for: signatures, key exchange, authentication

AES (Symmetric):

One shared key for both encryption and decryption
Very fast performance
Unlimited data size
Used for: bulk data encryption, file encryption

Best Practice: Use both together (hybrid encryption):

Generate random AES key
Encrypt data with AES (fast)
Encrypt AES key with RSA public key
Recipient decrypts AES key with RSA private key
Then decrypts data with AES key

See our AES Encryptor/Decryptor for symmetric encryption.

2. Is 2048-bit RSA still secure in 2025?

Yes, for most applications. Security assessments:

NIST: Approved through 2030 for most uses
BSI (Germany): Recommends 3000-bit from 2024
ANSSI (France): Recommends 2048-bit minimum
Industry: 2048-bit standard for TLS, SSH, PGP

Recommendations:

2048-bit: Standard for SSL/TLS, SSH, most applications
3072-bit: Enhanced security, future-proofing
4096-bit: Maximum security, long-term data protection

Quantum computing: RSA will be vulnerable when large-scale quantum computers exist (estimated 2030-2040). Plan migration to post-quantum algorithms.

3. Can someone derive my private key from my public key?

Theoretically possible, practically impossible. Breaking RSA requires factoring large prime numbers:

2048-bit RSA:

Estimated time to break: 2000+ years with current computers
Requires factoring 617-digit number
No efficient classical algorithm exists

Protection mechanisms:

Mathematical complexity (integer factorization problem)
Exponential time complexity
Regular key rotation adds additional security

Recommendation: Use 2048-bit minimum, rotate keys periodically, monitor quantum computing advances.

4. How should I store my private key?

Storage Security Hierarchy (best to worst):

Most Secure:

✅ Hardware Security Module (HSM)
✅ Password manager (encrypted vault)
✅ Encrypted disk with strong passphrase
✅ Password-protected PEM file

Moderate Security: 5. ⚠️ Unencrypted file with restricted permissions (chmod 600) 6. ⚠️ Secure notes application

Insecure: 7. ❌ Cloud storage without encryption 8. ❌ Email or messaging apps 9. ❌ Text files without permissions 10. ❌ Hardcoded in application source

Best Practices:

# Encrypt private key with password
openssl rsa -aes256 -in private_key.pem -out private_key_encrypted.pem

# Store in password manager as secure note
# Enable two-factor authentication on password manager
# Maintain encrypted backups in multiple locations

5. What’s the public exponent and why is it usually 65537?

The public exponent (e) is part of the public key used in RSA encryption.

Why 65537:

Binary: 10000000000000001 (only two 1-bits)
Very fast encryption operations
Sufficiently large to prevent attacks
Widely standardized (RFC 4871)

Alternative: 3 (faster but less secure, rarely used)

Security: The choice of public exponent doesn’t significantly affect RSA security - the key size and prime selection are far more important.

6. Can I use the same RSA key pair for both encryption and signing?

Technically yes, but not recommended.

Problems with key reuse:

Different security requirements for each use case
Increases attack surface
Complicates key rotation
Violates principle of separation of concerns

Best Practice:

Generate separate key pairs:
├── Encryption Keys
│   └── For confidential data encryption
├── Signing Keys
│   └── For digital signatures
├── Authentication Keys
│   └── For SSH, API access
└── TLS/SSL Keys
    └── For website certificates

Benefits of separation:

Independent key rotation schedules
Limited damage if one key compromised
Clear audit trails
Compliance with security standards

7. How do I convert between different key formats?

Using OpenSSL:

# PEM to DER
openssl rsa -in key.pem -outform DER -out key.der

# DER to PEM
openssl rsa -inform DER -in key.der -outform PEM -out key.pem

# PKCS#1 to PKCS#8
openssl pkcs8 -topk8 -in pkcs1.pem -out pkcs8.pem -nocrypt

# Extract public key from private key
openssl rsa -in private.pem -pubout -out public.pem

# Convert to SSH format
ssh-keygen -f public.pem -i -m PKCS8 > ssh_public.pub

# Add password protection
openssl rsa -aes256 -in private.pem -out private_encrypted.pem

Using our tool:

Generate keys in preferred format
Use format conversion feature
Export in multiple formats simultaneously

8. What happens if I lose my private key?

Consequences:

❌ Cannot decrypt data encrypted with your public key
❌ Cannot sign documents/transactions
❌ Cannot access SSH servers configured with your key
❌ Cannot access cryptocurrency wallets
❌ Cannot prove identity for authentication

No recovery possible - private keys cannot be regenerated or recovered.

Prevention strategies:

Backup Strategy:
├── Primary: Password manager (encrypted)
├── Secondary: Encrypted USB drive (offline)
├── Tertiary: Printed QR code (secure physical location)
└── Emergency: Encrypted cloud backup (separate service)

Test backups regularly!

If lost:

Generate new key pair immediately
Update all services with new public key
Revoke old key if possible (certificates)
Notify contacts of new public key
Review security of backup procedures

9. Are keys generated in the browser truly secure?

Yes, when using modern browsers. Our tool uses:

Web Crypto API:

Cryptographically secure random number generator
Native browser implementation (not JavaScript Math.random)
Hardware entropy sources where available
FIPS-validated in many browsers

Security verification:

// Our tool uses:
window.crypto.subtle.generateKey({
  name: "RSA-OAEP",
  modulusLength: 2048,
  publicExponent: new Uint8Array([1, 0, 1]), // 65537
  hash: "SHA-256"
}, true, ["encrypt", "decrypt"]);

Additional protections:

No network communication during generation
Keys never leave your browser
No logging or analytics
Secure memory handling

For maximum paranoia: Use offline key generation (air-gapped computer or hardware security module).

10. How often should I rotate RSA keys?

Depends on usage and security requirements:

High-security (recommended rotation):

Code signing keys: Annually
Root CA certificates: Every 5-10 years
API authentication: Every 6-12 months
Cryptocurrency wallets: When compromised or annually

Medium-security:

SSH keys: Every 1-2 years or when employee leaves
Email encryption: Every 2-3 years
TLS certificates: Follow CA requirements (typically annually)

Triggers for immediate rotation:

🚨 Private key compromised or suspected compromise
🚨 Employee with key access leaves company
🚨 Device with stored key lost or stolen
🚨 Security vulnerability in key generation method
🚨 Regulatory compliance requirements change

Rotation procedure:

Generate new key pair
Deploy public key to all services
Transition period (accept both old and new)
Revoke old public key
Securely delete old private key
Verify all services updated

References and Additional Resources

Internal Gray-wolf Tools

Complementary Security Tools:

AES Encryptor/Decryptor: Combine with RSA for hybrid encryption systems
Hash Generator: Generate fingerprints and verify key integrity
Password Strength Checker: Validate private key passphrase strength
Base64 Encoder: Encode keys for safe transmission and storage
UUID Generator: Generate unique identifiers for key management systems

Educational Resources

Learn More About Public Key Cryptography:

RSA Algorithm Explained
Digital Signatures and Authentication
Public Key Infrastructure (PKI)
Certificate Authorities and Trust Chains
Hybrid Encryption Systems

External Documentation

Standards and Specifications:

RSA Cryptography Standard (PKCS #1)
X.509 Certificate Standard
OpenSSH Public Key Format
JSON Web Key (JWK) Specification
NIST Digital Signature Standard (FIPS 186-4)

Last updated: November 3, 2025 | Tool Version: 2.1.0 | Maintained by Gray-wolf Security Team