export declare class HashHelper {
    /**
     * Generate a SHA-256 hash of a string.
     */
    static hash(content: string): string;
    /**
     * Generate an HMAC-SHA256 signature.
     */
    static signature(content: string, secret: string): string;
    /**
     * Verify that a content string matches the expected SHA-256 hash.
     */
    static verifyHash(content: string, expectedHash: string): boolean;
    /**
     * Verify that the HMAC-SHA256 signature of a string matches the expected value.
     */
    static verifySignature(content: string, secret: string, expectedSignature: string): boolean;
    /**
     * Safely compare two hashes or signatures in constant time.
     */
    private static safeCompare;
}