Key exchange
Key exchange is a cryptographic protocol by which communicating parties establish a shared secret over a communication channel without directly transmitting that secret.
Real-World Cryptography
A key exchange is a cryptographic protocol in which parties establish a common secret without directly transmitting that secret.
- How it is used
- Establishes a shared secret for authenticated encryption when communicating parties lack a pre-shared symmetric key.
- How deep it goes
- Explains key-pair generation, public-key exchange, shared-secret derivation, and MITM limits, while deferring detailed mathematics.
- Examples
- Uses Alice-and-Bob exchanges, private and public shapes, passive and active MITM scenarios, C code, RSA encapsulation, and Kyber intuition.
- What you can do after
- Apply it by deriving a shared secret for authenticated encryption while distinguishing passive observation from active impersonation.
Elliptic Curve Cryptography for Developers
A cryptographic process in which parties establish a common secret over a network without transmitting that secret directly.
- How it is used
- Establishes a shared secret for encrypting arbitrary-length messages with symmetric encryption over open networks.
- How deep it goes
- Builds elliptic-curve key generation and Diffie-Hellman computation, then tests MQV sharing; defers deeper Diffie-Hellman treatment.
- Examples
- Uses Alice-and-Bob exchange diagrams, passphrase-derived keys, elliptic-curve parameters, and an MQV test with matching hexadecimal shares.
- What you can do after
- Builds elliptic-curve key pairs, computes shared secrets, and verifies matching MQV outputs in code.
Read how Elliptic Curve Cryptography for Developers explains key exchange →
Related concepts
- 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.
- Diffie–Hellman key exchangeincludes · 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.
- public key cryptographyuses · Public-key cryptography is asymmetric cryptography that uses mathematically related public and private keys for encryption, decryption, signing, and verification.
- cryptographic primitivekind of · A cryptographic primitive is a fundamental algorithmic building block that provides a basic security function such as encryption, hashing, or digital signing.
- X3DHincludes · X3DH is a non-interactive key-exchange protocol that combines multiple Diffie-Hellman exchanges to establish shared keying material for asynchronous messaging.
- authenticated key exchangeincludes · A key exchange protocol that authenticates at least one party to prevent an active man-in-the-middle attacker from impersonating that party.
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