Monachus Digital Signature Extension is a free add-on for Chrome and Chromium-based Edge browsers. Developed by monachus.io, this extension offers PKI-based digital signatures using RSA keys on smart cards and tokens. It provides a range of functions for developers and web users.

One of the key features of this extension is the ability to select certificates. Users can view their signing certificates stored in smart cards, USB tokens, PFX files on their system, or the local certificate store in Windows environment. This makes it convenient to choose the appropriate certificate for signing.

Another useful function is the ability to sign data or hash values. The extension calculates the signature value by signing the data or hash with the private key of the selected certificate. This ensures the integrity and authenticity of the signed content.