Self-signed certificate

In cryptography and computer security, self-signed certificates are public key certificates that are not issued by a certificate authority (CA). These self-signed certificates are easy to make and do not cost money. However, they do not provide any trust value. For instance, if a website owner uses a self-signed certificate to provide HTTPS services, people who visit that website cannot be certain that they are connected to their intended destination. For all they know, a malicious third-party could be redirecting the connection using another self-signed certificate bearing the same holder name. The connection is still encrypted, but does not necessarily lead to its intended target. In comparison, a certificate signed by a trusted CA prevents this attack because the user's web browser separately validates the certificate against the issuing CA. The attacker's certificate fails this validation. Self-signed certificates can be created for free, using a wide variety of tools including OpenSSL, Java's keytool, Adobe Reader, wolfSSL and Apple's Keychain. They are easy to customize; e.g, they can have larger key sizes or hold additional metadata. Their use doesn't involve the problems of trusting third parties that may improperly sign certificates. Self-signed certificate transactions usually present a far smaller attack surface by eliminating both the complex certificate chain validation, and certificate revocation checks like CRL and OCSP. In a CA-based PKI system, parties engaged in secure communication must trust a CA, i.e. place the CA certificates in a whitelist of trusted certificates. Developers of web browsers may use procedures specified by the CA/Browser Forum to whitelist well-known, public certificate authorities. Individual groups and companies may whitelist additional, private CA certificates. The trust issues of an entity accepting a new self-signed certificate are similar to the issues of an entity trusting the addition of a new CA certificate.