"""
E2EE HKDF constants and helpers for Element Call compatibility.

The patched SDK (via patch_sdk.py + patched FFI binary) adds:
  - key_ring_size (int, field 5 in proto)
  - key_derivation_function (int, field 6: 0=PBKDF2, 1=HKDF)

This module provides constants and a convenience function for building
HKDF-compatible E2EE options.
"""

# Key derivation function constants matching proto enum KeyDerivationFunction
KDF_PBKDF2 = 0
KDF_HKDF = 1