export interface Keyring {
    current: string;
    keys: Record<string, Buffer>;
    /**
     * Which `enc1:` ciphertext rows are assumed to belong to. Defaults to
     * `RELAY_ENCRYPTION_LEGACY_KEY_ID` or "k1" if unset.
     */
    legacyKeyId: string;
}
/** True if the keyring is loaded + has at least one key (encryption active). */
export declare function isEncryptionActive(): boolean;
/**
 * v2.1 Phase 7p MED #2: eager startup validation for the keyring config.
 *
 * Pre-7p, keyring validation was purely lazy — `loadKeyring()` ran on first
 * encrypt/decrypt, and `getKeyringInfo()` swallowed errors as "encryption
 * inactive". Ambiguous configs (e.g. both `RELAY_ENCRYPTION_KEYRING` and
 * `RELAY_ENCRYPTION_KEY` set) let the daemon boot and only surfaced on the
 * first encrypted-column code path. The documented contract is "reject at
 * startup"; this makes the contract actually load-bearing.
 *
 * Called from `validateConfigAndEnv()` in src/config.ts. Throws on any
 * config error — multi-source, malformed JSON, bad key size, unreadable
 * path, etc. Returns silently when the config is valid (or when no
 * encryption is configured at all — that's a legitimate "plaintext mode"
 * choice, not an error).
 */
export declare function validateKeyringStrict(): void;
/** Return keyring info suitable for dashboards — NEVER exposes raw keys. */
export declare function getKeyringInfo(): {
    current: string | null;
    known_key_ids: string[];
    legacy_key_id: string;
};
/**
 * ADR-0003 (v2.20.0): derive a purpose-bound subkey from the keyring's CURRENT
 * key via HKDF-SHA256, WITHOUT exposing the raw keyring key outside this module
 * (the raw AES keys never leave encryption.ts — callers get only a domain-
 * separated derivative). Used by the token-lookup index to key its HMAC so a
 * DB-only read cannot offline-match a stolen token list against `token_lookup`.
 *
 * `info` is the HKDF context string — pass a stable, unique domain label per
 * use (e.g. "bot-relay/token-lookup/v1"). Returns a 32-byte subkey, or `null`
 * when no keyring is configured (plaintext mode) — callers must have their own
 * no-keyring fallback. The subkey rotates with the keyring: derivation reads
 * `kr.current`, so a keyring rotation yields a new subkey (and the token-lookup
 * layer re-populates lazily on the O(N) fallback path — the same graceful
 * behavior as first-time migration).
 */
export declare function deriveKeyringSubkey(info: string): Buffer | null;
/**
 * Whether `RELAY_ENCRYPTION_KEY` is being used — flag so callers can emit
 * the one-time deprecation warning at startup.
 */
export declare function isLegacyEnvKeyInUse(): boolean;
/** Whether the runtime has opted into RELAY_LAZY_REENCRYPT (reserved signal). */
export declare function isLazyReencryptEnabled(): boolean;
/**
 * Encrypt a plaintext string for at-rest storage. Emits the v2 versioned
 * prefix `enc:<key_id>:<iv>:<payload>` using the keyring's current key.
 * Returns plaintext unchanged when no keyring is configured.
 */
export declare function encryptContent(plaintext: string): string;
/**
 * Decrypt an at-rest string. Handles v2 versioned (enc:key_id:...),
 * legacy v1 (enc1:...), and plaintext pass-through uniformly. READ paths
 * stay pure — no side effects, no writes. See the READ-paths-stay-pure design note "READ paths stay
 * pure" discipline note.
 */
export declare function decryptContent(stored: string | null): string | null;
/**
 * Re-encrypt an existing ciphertext row with a target key_id. Used by
 * `relay re-encrypt` for the migration pipeline. Parses the input, decrypts
 * via its native key_id (handles both v2 and legacy v1 inputs), re-encrypts
 * with the target.
 *
 * The target key MUST be in the current keyring. Caller is responsible for
 * ensuring the source key is also resolvable (error will surface otherwise).
 */
export declare function reencryptRow(stored: string, toKeyId: string): string;
/**
 * Reset cached state — used exclusively by tests that mutate the env
 * between cases. Not exported in the public API contract.
 */
export declare function _resetKeyringCacheForTests(): void;
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