Table 1.

Main considerations evaluated in this study.

Security considerationsa	Description
Use of secured connections (SSLb/TLSc)	The use of any unsecured connections
SSL/TLS version	Evaluating the supported versions of SSL/TLS
Key exchange support	The cryptographic algorithm used to exchange the keys during the handshake for the following symmetric encryption
Cipher support	The cipher negotiated between client and server dictates what symmetric encryption is applied after the handshake and key exchange
Certificates	The security characteristics TLS offers rely on the server’s certificate. Any trust issues here are critical
Vulnerabilities	Certain attacks are based on specific implementations or the absence of a patch on the server
HSTSd	Support HSTS can prevent downgrades to HTTP

^aAll but the first one (use of unsecure connections) are tested for by the tools presented in later sections.

^bSSL: Secure Socket Layer.

^cTSL: Transport Layer Security.

^dHSTS: Hypertext Transfer Protocol Strict Transport Security.