Certificate Authority (CA) definition in Cybersecurity

A Certificate Authority (CA) is an entity that issues digital certificates. The 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 assertions made by the private key that corresponds to the certified public key. CAs are a critical component of the SSL/TLS ecosystem, providing verification of the certificate holder's identity and facilitating secure communication on the internet.

Open source or Free solutions

1. Let's Encrypt: An automated, open CA providing free SSL/TLS certificates, aiming to lower the barriers to secure web communications.
2. EJBCA: An open source PKI Certificate Authority software, allowing organizations to build and manage their own public key infrastructure.

Paying solutions

1. DigiCert: A leading global CA, offering a wide range of SSL/TLS certificates and related security services.
2. Sectigo: Offers SSL/TLS certificates and comprehensive web security solutions, including managed PKI services for businesses of all sizes.