/**
 * Generates a secure random 24 byte nonce.
 */
export declare function generateNonce(): string;
/**
 * Generates a secure random 96 byte, 128 character code verifier based on recommendations
 * in RFC 7636 which states code_verifier = high-entropy cryptographic random STRING using the
 * unreserved characters [A-Z] / [a-z] / [0-9] / "-" / "." / "_" / "~"
 * from Section 2.3 of [RFC3986], with a minimum length of 43 characters
 * and a maximum length of 128 characters.
 */
export declare function generateCodeVerifier(): string;
/**
 * The calculated code verifier challenge.
 */
export interface CodeVerifierChallenge {
    readonly challenge: string;
    readonly method: string;
}
/**
 * Generates a code challenge based on the code verifier using the SHA-256 hash algorithm.
 */
export declare function generateCodeVerifierChallenge(codeVerifier: string): CodeVerifierChallenge;
/**
 * Generates a 128bit random state string.
 */
export declare function generateState(): string;
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