# Why Stream Ciphers can be slower in software than Block Ciphers

I made some tests on virtual environment (Virtual Box) using StrongSwan, a VPN based on IPSec. I had latency results using ping command saying that Chacha20 (stream cipher) had poor performance comparing with AES and BLowfish (Block ciphers).

How is this possible since stream ciphers should be faster than block ciphers?

• Why do you think stream ciphers should be faster? AES is typically slower than ChaCha20 in pure software, but faster if you have hardware acceleration such as AESNI which almost all x86 processors have these days. Jun 29 '19 at 21:28
• Well I think this based in many tests with strongswan (IPSEC), using aes, 3des, blowfish and chacha20 as cipher. All tests using block ciphers algorythms had less latency than stream cipher. The test were made with virtual machines. Jun 30 '19 at 22:05

openssl speed -evp aes-128-ctr