TLS 1.3 Performance Part 6 – Throughput

Some interesting results were found when comparing the throughput of TLS 1.2 and TLS 1.3 using an assembly optimized wolfSSL – some good, some bad. This is the last of the blogs discussing the performance differences observed between TLS 1.2 and TLS 1.3 in wolfSSL and how to make the most of them in your applications. There are differences in the way the data is encrypted in TLS 1.2 and 1.3. For some algorithms this makes a noticeable difference.

TLS 1.2 encrypts the plaintext of the message and generates an authentication code on the encrypted data plus additional_data which includes: a 64-bit sequence number, 1 byte content type, 2 byte version and 2 byte length. This is a total of 13 extra bytes in additional_data.

TLS 1.3 encrypts the plaintext of the message plus one byte for the real record type and generates an authentication code on the encrypted data plus the record header of 5 bytes.

For AES-GCM cipher suites the throughput was observed to be slightly increased with the Intel x86 64-bit optimized assembly code. This is due to the number of bytes passed in as additional authentication data (AAD). The AAD bytes are processed separately before encryption and decryption and it turned out processing 5 bytes was faster than 13. The extra byte on the end of the encrypted data did not have a significant impact.

For Chacha20-Poly1305 the different size of data passed in as AAD has no significant impact as the data is placed into a 16 byte block and padded before being processed. But, the extra byte at the end of the plaintext did impact the Chacha20 and Poly1305 performance. For Poly1305, the extra byte resulted in an extra 16 byte block being processed. In total this had about a 3-5% impact on throughput with the Intel x86 64-bit optimized assembly code.

TLS 1.3 has better throughput when using AES-GCM and is another reason to change. For maximum throughput consider sending one less than the maximum plaintext size, by default 16384 bytes, in an application data message. This will have a positive impact for both AES-GCM and Chacha20-Poly1305 cipher suites.

Part 1 (TLS 1.3 Performance – Resumption)
Part 2 (TLS 1.3 Performance – Full Handshake)
Part 3 (TLS 1.3 Performance – Pre-Shared Key (PSK))
Part 4 (TLS 1.3 Performance – Server Pre-Generation)
Part 5 (TLS 1.3 Performance – Client-Server Authentication)