OperaCrypt

This extension allows encrypting or decrypting pieces of text selected from a Web page. It uses the same password for both encrypting and decrypting. The encryption process is based on the well-known Advanced Encryption Standard (AES) symmetric algorithm. All the required tasks are performed by the extension itself with no intervention of external tools or services. This extension can be useful for scenarios such as maintaining encrypted sections in a wiki, sending secure email messages through a Webmail application, etc.