/**
 * hmem-sync crypto layer
 *
 * Key derivation: scrypt (Node.js built-in crypto, memory-hard, no native deps)
 * Encryption:     AES-256-GCM (authenticated, per-blob random IV)
 * Recovery key:   Base58-encoded 16 random bytes (24 chars displayed as groups)
 *
 * Zero-knowledge design:
 *   - The server never sees plaintext content, IDs, or the passphrase.
 *   - Each blob has its own random 12-byte IV — reuse is impossible.
 *   - The salt is stored server-side (public) — it protects against rainbow tables
 *     but the server cannot derive the key without the passphrase.
 */
export interface EncryptedBlob {
    /** Base64-encoded: IV (12) + ciphertext + auth tag (16) */
    data: string;
    /** ISO timestamp of when this blob was encrypted (for delta sync) */
    updated_at: string;
}
export interface SyncKeyMaterial {
    /** Base64-encoded 32-byte salt — stored server-side, never secret */
    salt: string;
    /** Human-readable recovery key (Base58, grouped with dashes) */
    recoveryKey: string;
}
/**
 * Derive a 256-bit AES key from a passphrase + salt using scrypt.
 * The salt must be stored server-side and retrieved before any crypto operation.
 */
export declare function deriveKey(passphrase: string, saltBase64: string): Buffer;
/**
 * Encrypt plaintext with AES-256-GCM.
 * Returns a single Base64 blob: IV + ciphertext + auth tag.
 */
export declare function encrypt(plaintext: string, key: Buffer): string;
/**
 * Decrypt a blob produced by encrypt().
 * Throws if the auth tag doesn't match (tampered or wrong key).
 */
export declare function decrypt(blobBase64: string, key: Buffer): string;
/**
 * Generate a new random salt and recovery key for a fresh sync setup.
 * Call once per user — store salt server-side, give recovery key to user.
 */
export declare function generateKeyMaterial(): SyncKeyMaterial;
export declare function base58Decode(str: string): Buffer;
/**
 * Encrypt a single hmem entry's content fields into a blob.
 * The entry_id_hash (SHA-256 of entry ID) is stored unencrypted server-side
 * for delta detection — no plaintext ID leaks to the server.
 */
export declare function encryptEntry(entryId: string, payload: Record<string, unknown>, key: Buffer, updatedAt: string): EncryptedBlob;
export declare function decryptEntry(blob: EncryptedBlob, key: Buffer): Record<string, unknown>;