GCM (Galois/Counter Mode) and GMAC (GCM MAC)

modulename: gcm.ko

configname: CONFIG_CRYPTO_GCM

Linux Kernel Configuration
└─>Cryptographic API
└─>AEAD (authenticated encryption with associated data) ciphers
└─>GCM (Galois/Counter Mode) and GMAC (GCM MAC)
In linux kernel since version 2.6.25 (release Date: 2008-04-16)  
GCM (Galois/Counter Mode) authenticated encryption mode and GMAC
(GCM Message Authentication Code) (NIST SP800-38D)

This is required for IPSec ESP (XFRM_ESP).

source code: