TLS libraries
There is few crypto libraries for TLS that works on OpenWrt:
- OpenSSL is a de-facto standard. It's libopenssl takes more than a 1Mb of disk space.
- MbedTLS is a small library developed for embedded devices. Was used by default in OpenWrt before.
- WolfSSL is a small library developed for embedded devices. Supports TLS1.3. Installed by default in OpenWrt 21. But in future this may be changed back to MbedTLS.
- Nettle just a small crypto library without TLS support.
- GnuTLS is GNU project but not often used. Internally uses Nettle.
- LibTomCrypt: used internally in Dropbear SSH daemon. It's not a TLS lib that you may use but all routers have it.
When you are installing some program you may check which library you already have and install a specific version to reuse existing dependency.
For example rtty daemon has three versions rtty-mbedtls, rtty-openssl, rtty-wolfssl. Some OpenWrt only packages like kadnode uses only mbedtls and other libraries aren't supported yet.
See also Comparison of TLS implementations