# Class PkceChallenge

java.lang.Object
com.codename1.io.oidc.PkceChallenge

public final class PkceChallenge extends Object

One PKCE pair (RFC 7636). The `code_verifier` is kept by the client; the `code_challenge` (always `S256` here) is sent to the authorization endpoint; the verifier is then presented to the token endpoint to prove possession.

PKCE is mandatory on every authorization-code flow this client initiates, even when a `client_secret` is configured -- providers like Google and Microsoft both require it for mobile public clients and tolerate it for confidential clients.

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `static final String`
  `METHOD_S256`
  Always `"S256"` -- the only value `OidcClient` emits.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static PkceChallenge`
  `generate()`
  Generates a fresh PKCE pair with a 64-byte (~86 char) verifier.
  `String`
  `getChallenge()`
  The challenge to include on the authorization URL as `code_challenge`.
  `String`
  `getMethod()`
  Always returns `METHOD_S256`.
  `String`
  `getVerifier()`
  The verifier that must be supplied to the token endpoint as `code_verifier`.

  ### Methods inherited from class Object

  `clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- ## Field Details

  - ### METHOD_S256

    public static final String METHOD_S256
    Always `"S256"` -- the only value `OidcClient` emits. RFC 7636 also defines `"plain"` but it is forbidden by this client.
    See Also:
      - Constant Field Values

- ## Method Details

  - ### generate

    public static PkceChallenge generate()
    Generates a fresh PKCE pair with a 64-byte (~86 char) verifier. The verifier characters are drawn from the unreserved set `[A-Z][a-z][0-9]-._~` via base64url encoding of secure random bytes, per RFC 7636 section 4.1.

  - ### getVerifier

    public String getVerifier()
    The verifier that must be supplied to the token endpoint as `code_verifier`.

  - ### getChallenge

    public String getChallenge()
    The challenge to include on the authorization URL as `code_challenge`.

  - ### getMethod

    public String getMethod()
    Always returns `METHOD_S256`.