Diffie–Hellman key exchange
Diffie–Hellman key exchange is a public-key key-agreement protocol that enables parties to derive a shared secret over an insecure channel without transmitting it.
Real-World Cryptography
Diffie-Hellman key exchange is a public-key protocol that lets parties establish a shared secret over an insecure channel.
- How it is used
- Establishes a shared secret over an insecure channel for later symmetric encryption.
- How deep it goes
- Explains the exchange, modular key formulas, discrete-logarithm basis, standards, and authentication limits.
- Examples
- Uses Alice-and-Bob shape combinations and modular arithmetic with generator 3 and prime 5.
- What you can do after
- Operate/configure DH using suitable parameters, validate received public keys, and distinguish passive from active MITM risks.
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Hacking Cryptography
Diffie–Hellman key exchange is a key-agreement protocol in which participants derive a shared secret from exchanged public values and retained private exponents.
- How it is used
- Establishes shared secrets for public-key cryptography and key exchanges in TLS.
- How deep it goes
- Derives public values and shared-secret equations through modular arithmetic, without implementation code or parameter-selection guidance.
- Examples
- Works through Alice and Bob using p = 13, g = 7, private exponents 3 and 9, and shared secret 5.
- What you can do after
- Evaluate how public values produce a shared secret without exposing either private exponent.
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Elliptic Curve Cryptography for Developers
A public-key key-agreement protocol that lets parties establish a shared secret over an insecure network using private values and exchanged public values.
- How it is used
- Uses elliptic-curve public keys to establish a secret for a symmetric encryption algorithm.
- How deep it goes
- Explains the exchange flow and test implementation, but defers detailed curve and prime selection.
- Examples
- Demonstrates reciprocal multiprecision calculations with pass-phrase and random private-key inputs, producing matching hexadecimal shares.
- What you can do after
- Build a testable elliptic-curve exchange and verify that both parties compute identical shared key material.
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Software Security for Developers
Diffie-Hellman is a public-key key-agreement algorithm based on the computational difficulty of the discrete logarithm problem.
- How it is used
- Uses public-key agreement to establish a symmetric encryption key across an insecure communication channel.
- How deep it goes
- Explains exchanged keys, private-key protection, equivalent computations, and the untransmitted shared secret, while deferring mathematical detail.
- Examples
- Uses a public-chat analogy, an ACME payment-and-warehouse scenario, and a shared-secret computation equation.
- What you can do after
- Evaluate how DH establishes an AES key and distinguish its role from the encryption of application data.
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Related concepts
- X3DHused by · X3DH is a non-interactive key-exchange protocol that combines multiple Diffie-Hellman exchanges to establish shared keying material for asynchronous messaging.
- API keyproduces · An API key is a credential used to identify or authorize a client accessing an application programming interface.
- key exchangekind of · Key exchange is a cryptographic protocol by which communicating parties establish a shared secret over a communication channel without directly transmitting that secret.
- elliptic-curve diffie-hellmanincludes · Elliptic-curve Diffie-Hellman is a public-key key-agreement method in which parties derive a shared secret through elliptic-curve point operations.
- CPaceused by · CPace is a symmetric password-authenticated key-exchange algorithm in which parties derive a group generator from a shared password and use it for ephemeral Diffie-Hellman key exchange.
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