/**
 * Save private key to OS keychain.
 * macOS: Keychain Access (security command)
 * Linux: libsecret / GNOME Keyring (secret-tool)
 * Returns false if keychain is unavailable or save failed.
 */
export declare function saveToKeychain(walletName: string, privateKey: string): Promise<boolean>;
/**
 * Load private key from OS keychain.
 * Returns null if not found or keychain unavailable.
 */
export declare function loadFromKeychain(walletName: string): Promise<string | null>;
/**
 * Delete private key from OS keychain.
 */
export declare function deleteFromKeychain(walletName: string): Promise<void>;
/**
 * Save both EVM and Solana keys to OS keychain under `{walletName}-evm` and `{walletName}-solana`.
 */
export declare function saveAllToKeychain(walletName: string, evmKey: string, solanaKey: string): Promise<boolean>;
/**
 * Load both EVM and Solana keys from OS keychain.
 * Falls back to legacy single-key entry if new-format entries don't exist.
 */
export declare function loadAllFromKeychain(walletName: string): Promise<{
    evm: string | null;
    solana: string | null;
}>;
/**
 * Check if OS keychain is available.
 */
export declare function isKeychainAvailable(): boolean;
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