Diffie-Hellman Key Exchange
Online Diffie-Hellman key exchange tool with ECDH and X25519 negotiation, two-party public key exchange, and shared-secret verification for TLS demos, secure channel debugging, and cryptography learning.
How Diffie-Hellman Works
Alice and Bob generate key pairs, exchange public keys, and derive the same shared secret independently. Even if public keys are intercepted, the shared secret cannot be directly recovered.
Algorithm Settings
Derived length controls the final shared-secret output size.
Alice
(shown after key generation)
(shown after key generation)
Bob
(shown after key generation)
(shown after key generation)
Quick Demo (Auto Mode)
Click the button below to run the full key exchange flow automatically.
About Diffie-Hellman Key Exchange
Diffie-Hellman is a foundational public-key key agreement mechanism used in TLS, SSH, VPN, and modern secure communication protocols.
Key Characteristics
- Secure key agreement over untrusted channels
- ECDH provides shorter keys with strong security
- Supports forward secrecy for session protection
- Can be combined with certificates for identity verification
ECDH vs Traditional DH
- Shorter keys: ECDH 256-bit security is close to DH 3072-bit level
- Better performance: elliptic-curve operations are efficient in practice
- Wider modern adoption in browsers and security stacks
Security Notes
- Always verify peer public-key identity to prevent MITM attacks
- Use ephemeral key pairs for each session
- Apply HKDF or another KDF before direct key usage
- Use certificates, signatures, and key rotation in production
Common Use Cases
- TLS/HTTPS session key negotiation
- SSH secure remote session establishment
- VPN tunnel key agreement (for example, WireGuard)
- End-to-end encrypted messaging session setup