ngtcp2_crypto_update_key
========================

Synopsis
--------

*#include <ngtcp2/ngtcp2_crypto.h>*

.. function:: int ngtcp2_crypto_update_key( ngtcp2_conn *conn, uint8_t *rx_secret, uint8_t *tx_secret, ngtcp2_crypto_aead_ctx *rx_aead_ctx, uint8_t *rx_key, uint8_t *rx_iv, ngtcp2_crypto_aead_ctx *tx_aead_ctx, uint8_t *tx_key, uint8_t *tx_iv, const uint8_t *current_rx_secret, const uint8_t *current_tx_secret, size_t secretlen)

    
    `ngtcp2_crypto_update_key` updates traffic keying materials.
    
    The new decryption traffic secret is written to the buffer pointed
    by *rx_secret*.  The length of secret is *secretlen* bytes, and
    *rx_secret* must point to the buffer which has enough capacity.
    
    The new encryption traffic secret is written to the buffer pointed
    by *tx_secret*.  The length of secret is *secretlen* bytes, and
    *tx_secret* must point to the buffer which has enough capacity.
    
    The derived decryption packet protection key is written to the
    buffer pointed by *rx_key*.  The derived decryption packet
    protection IV is written to the buffer pointed by *rx_iv*.
    *rx_aead_ctx* is initialized with the derived key and IV.
    
    The derived encryption packet protection key is written to the
    buffer pointed by *tx_key*.  The derived encryption packet
    protection IV is written to the buffer pointed by *tx_iv*.
    *tx_aead_ctx* is initialized with the derived key and IV.
    
    *current_rx_secret* and *current_tx_secret* are the current
    decryption and encryption traffic secrets respectively.  They share
    the same length with *rx_secret* and *tx_secret*.
    
    The length of packet protection key and header protection key is
    `ngtcp2_crypto_aead_keylen(ctx->aead) <ngtcp2_crypto_aead_keylen>`,
    and the length of packet protection IV is
    `ngtcp2_crypto_packet_protection_ivlen(ctx->aead)
    <ngtcp2_crypto_packet_protection_ivlen>` where ctx is obtained by
    `ngtcp2_crypto_ctx_tls`.
    
    This function returns 0 if it succeeds, or -1.