s2n-tls, originally named s2n, is an open-source C99 implementation of the Transport Layer Security (TLS) protocol developed by Amazon Web Services (AWS) and initially released in 2015.

[4] AWS said that the name "s2n" stands for signal to noise as a nod "to the almost magical act of encryption—disguising meaningful signals, like your critical data, as seemingly random noise".

s2n-tls supports the main ciphers in use today, such as AES in CBC and GCM modes, 3DES, and RC4.

It also provides support for perfect forward secrecy through Diffie–Hellman or Elliptic-curve Diffie–Hellman ephemeral keys.

Weaker ciphers and key exchange modes are disabled by default.