/**
 * PKCE (Proof Key for Code Exchange) utilities
 * RFC 7636: https://datatracker.ietf.org/doc/html/rfc7636
 */
/**
 * Generate a cryptographically random code verifier
 * Must be 43-128 characters long, using [A-Z][a-z][0-9]-._~
 */
export declare function generateCodeVerifier(): string;
/**
 * Generate code challenge from verifier using S256 method
 * code_challenge = BASE64URL(SHA256(ASCII(code_verifier)))
 */
export declare function generateCodeChallenge(verifier: string): string;
/**
 * Generate a random state parameter for CSRF protection
 */
export declare function generateState(): string;
/**
 * PKCE parameters for authorization flow
 */
export interface PKCEParams {
    codeVerifier: string;
    codeChallenge: string;
    state: string;
}
/**
 * Generate all PKCE parameters needed for authorization
 */
export declare function generatePKCEParams(): PKCEParams;
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