Performance Comparison: TLS 1.3 in wolfSSL and OpenSSL

The performance of TLS 1.3 using wolfSSL has recently been discussed here in the blogs. While checking our performance a comparison was made with OpenSSL. An OpenSSL server using the latest TLS 1.3 implementation at the time was used with the wolfSSL client. The numbers showed that the recent Intel x86 64-bit assembly optimizations have been worth it.

Firstly, the performance of PSK without key exchange is mostly dependent on the speed of the hash algorithm. The results showed that the small block performance of SHA-256 in wolfSSL was the difference. On the platform tested, wolfSSL is about 22% faster than OpenSSL at hashing 256 bytes. The performance of wolfSSL in PSK non-KE handshakes was about 19% better than that of OpenSSL. The improved hashing performance partially helped other results.

The performance of other TLS 1.3 handshakes is dominated by the public key operations. Note that OpenSSL did not negotiate DH with TLS 1.3 in the version tested. When using PSK with a key exchange the public key operations the server performs are: ECDH key generation and secret calculation. While these operations in wolfSSL are only around 7% faster than OpenSSL on the platform the overall handshake performance was about 36% better. The overheads around performing the cryptographic operations in OpenSSL and slower hashing during the handshake made up the difference.

When using RSA certificates for server authentication, the cost of signing outweighs any other operation. On the platform RSA signing is about the same speed in wolfSSL as OpenSSL. The overall handshake speed was 10-15% better than OpenSSL due to overheads and hashing.

P-256 operations are faster in wolfSSL than OpenSSL and the overheads and hashing difference once again impacted the results. The server is performing key generation, secret generation, and signing operations. wolfSSL is 7-13% faster at performing these operations with P-256 on the platform and about 3% faster performing X25519 operations. wolfSSL was seen to be 35-40% faster than OpenSSL when using P-256 and 20-30% faster when Curve25519 is used for key exchange. When client authentication was also performed, similar improvements were seen.

Performance increases like 35-40% are real reasons to use wolfSSL rather than OpenSSL for TLS 1.3 and especially on Intel x86 64-bit.

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