With Adobe Sign, you get everything you need to comply with a range of signer authentication and document validation requirements. For most transactions, a standard e-signature is enough. It can be authenticated using one or more factors such as email, text message, or password. Other transactions require more advanced forms of authentication. When you use digital signatures, each signer is issued a certificate-based digital ID by a trusted Certificate Authority (CA), and signing is backed by public key infrastructure (PKI) technology.