(C) AEAD AES 128-bit GCM. Demonstrates AES encryption using the Galois/Counter Mode (GCM). GCM is an authenticated encryption mode with "additional data" (often referred to as AEAD). GCM is a cipher mode that can be applied to any symmetric encryption algorithm with a 16-byte block size, such as AES …
Quick Benchmark: CBC vs GCM AES-128-GCM without HW acceleration Phaeo:~$ openssl speed -evp aes-128-gcm aes-128-gcm 7069.21k 7351.37k 7416.55k 7444.96k 7405.68k The Cortex-A9 is my RT-AC56U where I run OpenVPN server. It doesn't have any crypto acceleration in HW. CBC is faster than GCM by 145% to 185%. Security for VPNs with IPsec Configuration Guide, Cisco Sep 02, 2018
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 is a TLSv1.2 cipher suite. It can not be used with SSLv3 or TLSv1. Also, it might not be even available for the unknown
AES can be used with 128,192, and 256-bit key sizes and always with 128-bit block size †.. In NIST 800-38d, GCM is defined for 128-bit block size, since it is operating on block size and doesn't mandate about the key size.. This Recommendation specifies an algorithm called Galois/Counter Mode (GCM) for authenticated encryption with associated data.
The AES-GCM mode of operation can actually be carried out in parallel both for encryption and decryption. The additional security that this method provides also allows the VPN use only a 128 bit key, whereas AES-CBC typically requires a 256 bit key to be considered secure. You are able to use GCM ciphers (such as aes-128-gcm) on any of our
Cipher suite - Wikipedia