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Subject public key info

As explained in Software Security for Developers

Subject Public Key Info is the X.509 certificate structure that contains a subject public key and identifies its key algorithm or type.

Subject Public Key Info is the X.509 certificate structure that carries a subject’s public-key value and identifies the key algorithm or type. It helps software determine which public key belongs to the certificate’s subject. section 8.1.4

A Subject Public Key Info section identifies:

  • The public-key value itself. section 8.1.4
  • The public-key algorithm or type, such as an elliptic-curve key. section 8.1.4
  • Key parameters, such as a 256-bit size and the P-256 curve for an elliptic-curve key. section 8.1.4

GitHub’s certificate

A GitHub certificate lists id-ecPublicKey, a 256-bit public key, and the NIST P-256 curve. OpenSSL can extract and decode this key for inspection.

How Software Security for Developers covers it

How deep it goes
Explains the structure through key values, algorithms, sizes, and curve parameters, without covering cryptographic mathematics.
Examples
Uses GitHub’s certificate and OpenSSL commands to show a P-256 public key and its decoded representation.
What you can do after
Evaluate certificate public-key details by extracting and decoding them with OpenSSL.
How it connects
Connects X.509 certificates with subjects, Subject Alternative Names, RSA, and elliptic-curve public keys.
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Related concepts

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