In cryptography, a certificate authority or certification authority (CA) is an entity that issues digital certificates.

A digital certificate certifies the ownership of a public key by the named subject of the certificate.

This allows others (relying parties) to rely upon signatures or on assertions made about the private key that corresponds to the certified public key.

A CA acts as a trusted third party—trusted both by the subject (owner) of the certificate and by the party relying upon the certificate.

The format of these certificates is specified by the X.509 standard.

Let's Encrypt is a certificate authority that provides free X.509 certificates for Transport Layer Security (TLS) encryption via an automated process designed to eliminate the hitherto complex process of manual creation, validation, signing, installation, and renewal of certificates for secure websites.

It launched on April 12, 2016.

The Internet Security Research Group (ISRG) is a Californian public-benefit corporation which focuses on Internet security.

Transport Layer Security (TLS) – and its predecessor, Secure Sockets Layer (SSL), which is now deprecated by the Internet Engineering Task Force (IETF) – are cryptographic protocols that provide communications security over a computer network.

Several versions of the protocols find widespread use in applications such as web browsing, email, instant messaging, and voice over IP (VoIP).

Websites are able to use TLS to secure all communications between their servers and web browsers.

Intuitive Surgical Inc. is an American corporation that develops, manufactures and markets robotic products designed to improve clinical outcomes of patients through minimally invasive surgery, most notably with the da Vinci Surgical System.

The company is part of the NASDAQ-100 and S&P 500.

As of September 30, 2017, there was an installed base of 4,271 units worldwide – 2,770 in the United States, 719 in Europe, 561 in Asia, and 221 in the rest of the world.