Function deriveKey

deriveKey(
    ikm: string | Uint8Array<ArrayBufferLike>,
    salt?: string | Uint8Array<ArrayBufferLike>,
    info?: string | Uint8Array<ArrayBufferLike>,
    keylen?: number,
): Promise<Buffer<ArrayBufferLike>>
Derive a key with HKDF-SHA256.
Parameters
- ikm: string | Uint8Array<ArrayBufferLike>
  Input key material (e.g. a session token).
- Optionalsalt: string | Uint8Array<ArrayBufferLike>
  Optional salt. Default: empty.
- info: string | Uint8Array<ArrayBufferLike> = 'anza-stui-session-v1'
  Context string. Default 'anza-stui-session-v1'.
- keylen: number = 32
  Output length in bytes. Default 32; keep it at 32 or more, since HMAC signing and verification reject shorter secrets.
Returns Promise<Buffer<ArrayBufferLike>>
The derived key.
Throws
AnzaError CRYPTO (as a rejection) when derivation fails.
Example
```
import { crypto as anzaCrypto, verifyEnvelope } from '@anzaui/engine';

const userKey = await anzaCrypto.hkdf.deriveKey(sessionToken, 'anza-cluster-salt-2026', 'user-live-feed', 32);
verifyEnvelope({ mode: 'hmac', secret: userKey }, envelope, { maxAgeSecs: 60, slot: 'feed' });
```
- Defined in src/crypto/hkdf.ts:36