Public key
A public key is the openly distributable component of an asymmetric cryptographic key pair, used for encryption, authentication, or signature verification.
Software Security for Developers
A public key is the openly distributable member of a cryptographic key pair used for operations such as encryption or signature verification.
- How it is used
- Solves key distribution and supports encryption, signature verification, service authentication, certificates, TLS, and WebAuthn.
- How deep it goes
- Explains paired-key behavior, certificates, RSA workflows, hybrid encryption, and service signatures, but defers mathematical proofs.
- Examples
- Demonstrates refund encryption, service-request signatures, X.509 certificate inspection, and hardware-key registration and authentication.
- What you can do after
- Build it from scratch by generating key pairs, encrypting with public keys, decrypting with private keys, and verifying RSA signatures.
Read how Software Security for Developers explains public key →
Real-World Cryptography
A value in a public-key cryptosystem that may be distributed openly for verification or encryption operations.
- How it is used
- Supports encryption, shared-secret establishment, signature verification, and trust decisions in asymmetric cryptographic protocols.
- How deep it goes
- Explains public/private roles and protocol flows, but defers primitive-specific mathematics and detailed implementation internals.
- Examples
- Uses Diffie-Hellman shapes, encrypted email, RSA signatures, device pairing, PGP trust, and Bitcoin transactions.
- What you can do after
- Apply it via key-exchange, encryption, signature-verification, device-pairing, and cryptocurrency workflows while recognizing unauthenticated-key risks.
Hacking Cryptography
The public key is the openly distributable member of an asymmetric key pair used for operations such as encryption or signature verification.
- How it is used
- Enables encryption to a recipient and verification of signatures without distributing the private key.
- How deep it goes
- Defines keypair roles and works through Diffie–Hellman and RSA calculations, while deferring the proof that RSA decryption works.
- Examples
- Uses a lock-and-key analogy, an Alice-and-Bob encryption flow, a modulo-13 Diffie–Hellman exchange, and numerical RSA encryption.
- What you can do after
- Evaluate/understand which asymmetric operation exposes a public key and which matching private-key operation remains secret.
Secure APIs
A public key is the openly distributable half of an asymmetric cryptographic key pair used to verify signatures or perform public-key operations.
- How it is used
- Validates JWT signatures while keeping token-signing authority in a separate private key.
- How deep it goes
- Explains key-pair roles and demonstrates PEM generation, loading, and PS256 validation, but defers broader key-management operations.
- Examples
- Demonstrates OpenSSL RSA generation, public_key.pem, and PyJWT validation with a PS256-signed token.
- What you can do after
- Operate PyJWT validation with a PEM public key, fixed algorithm, audience, and issuer.
Elliptic Curve Cryptography for Developers
A public key is a cryptographic value distributed openly and paired with a private key for encryption, signature verification, or related public-key operations.
- How it is used
- Enables shared-secret establishment and signature verification across open networks without prearranging a common secret.
- How deep it goes
- Derives elliptic-curve public keys as scalar multiples, relates security to ECDLP and curve order, and maps generation to C routines.
- Examples
- Uses Alice and Bob’s exchanged curve points, document-signature verification, a base-key structure, and key-generation routines.
- What you can do after
- Build it from scratch by deriving a public curve point from a private integer and base point, then using it in exchange or verification.
Read how Elliptic Curve Cryptography for Developers explains public key →
API Design Patterns
A public key is the openly distributable component of an asymmetric cryptographic key pair used to verify signatures or perform other public-key operations.
- How it is used
- Authenticates API requests by letting servers verify signatures without receiving users’ private keys.
- How deep it goes
- Traces generation, registration, signature verification, request metadata, and digest validation, but defers cryptographic number theory.
- Examples
- Demonstrates RSA key generation, PEM serialization, signature headers, and a signed PATCH request.
- What you can do after
- Build it from scratch by generating credentials, registering a public key, signing requests, and verifying inbound signatures.
Road to Kubernetes
A public SSH key is the shareable half of an SSH key pair used by a remote system to authenticate the corresponding private key.
- How it is used
- Enables GitHub Actions to connect to newly provisioned Akamai Connected Cloud instances without password input.
- How deep it goes
- Defines the key pair, demonstrates generation and console installation, and defers deeper SSH-key treatment to appendices.
- Examples
- Uses github_actions_key.pub, the Akamai SSH Keys console, and an NGINX installation workflow.
- What you can do after
- Operate/configure passwordless SSH by installing a public key on instances for GitHub Actions access.
ASP.NET Core in Action, 3e
A public key is a cryptographic key intended for distribution that can be used with its corresponding private key for encryption or verification.
- How it is used
- Supports HTTPS data encryption by letting browsers communicate securely with a server’s corresponding private key.
- How deep it goes
- Defines the public/private relationship and certificate trust chain, but stops short of cryptographic algorithms or implementation internals.
- Examples
- Uses browser-to-server encryption and an ASP.NET Core development certificate that produces an untrusted-certificate warning.
- What you can do after
- Evaluate HTTPS certificate warnings by separating encryption provided by the key pair from trust provided by certificate authorities.
Related concepts
- certificatepart of · A digital certificate is a digitally signed credential that binds an identity to a public key and supports authentication or secure communication.
- public-private key pairpart of · A public-private key pair is a mathematically related public key and private key used together for asymmetric cryptographic operations.
- digital signatureused by · A digital signature is cryptographic data generated with a private key and verified with corresponding public information to authenticate data or its signer and detect alteration.
- signature verificationused by · Signature verification is the cryptographic process of checking a digital signature against data and a corresponding public key to determine whether it is valid.
- private keycontrasts with · A private key is the secret component of an asymmetric cryptographic key pair used by its holder for operations such as authentication, decryption, or digital signing.
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