/**
 * Decrypts a base64url-encoded ciphertext using an Azure Key Vault key (A256CBC).
 * The initialization vector is read from a Key Vault secret.
 *
 * @param keyURL - The URL of the Azure Key Vault instance
 * @param keyName - The name of the key to use for decryption
 * @param payloadBase64 - The base64url-encoded ciphertext to decrypt
 * @param ivSecretName - The name of the secret containing the initialization vector
 * @returns A promise resolving to the decrypted plaintext string
 */
export declare function decryptData(keyURL: string, keyName: string, payloadBase64: string, ivSecretName: string): Promise<string>;